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Influence of a Global Magnetic Field on Ion and Atmospheric Loss and Planetary Habitability


This 3-day workshop will be held virtually on June 15-17th. Sessions will be hosted from 9am ET to 1:30pm ET, including a 30-minute break.

Topics of discussion will focus on atmospheric escape (including ion outflow) from planets and moons, and the influence of planetary magnetic fields and stellar inputs on atmospheric retention. There will be interactions between scientists representing diverse scientific disciplines (Heliophysics, Astrophysics, Astrobiology, and Planetary Science) and approaches (e.g. observations, modeling, theory). Abstracts related to the following concepts are encouraged:

  • Atmospheric escape from planets
  • Ion outflow from planets
  • Influence of magnetic fields on atmospheric escape
  • Atmospheric/ionospheric chemistry related to atmospheric escape
  • Influence of stellar outputs and their variability on atmospheric escape
  • Influence of atmospheric escape on planetary evolution
  • Influence of Ionosphere-Thermosphere coupling on atmospheric escape
  • Exoplanet atmospheric loss and star-planet interactions
  • Future challenges and connections to other scientific fields

Note: the word atmospheric escape includes neutral and ion escape processes and rates.

Register for the Workshop

To register for the workshop, simply fill out the Google Form. If you have questions or technical difficulties, please email peticola@sonoma.edu.

This workshop is hosted by the MACH Center, supported by NExSS, sponsored by NASA’s Heliophysics DRIVE program.

Workshop Program Schedule


The workshop program schedule is organized by day and session. Each day starts at 7:00AM Mountain Daylight Time and ends at 11:30AM Mountain Daylight Time. Each presentation below has an abstract associated with it, which can be found in the abstract tab above. Session Chairs and Support Team for each session is as follows: Tuesday, Session 1: Catherine Regan (support Cohen, Holmstrom); Tuesday, Session 2: Agnit Mukhopadhyay (support Cohen, Holmstrom); Wednesday, Session 1: Shotaro Sakai (support Seki); Thursday, Session 1: Kai Zhao (support Kistler); Thursday, Session 2: Yi Qi (support Ma).

Tuesday Session 1: Atmospheric Escape Processes and Drivers

Time (MDT) First Author Topic
7:00AM David Brain

Welcome

7:05AM Ruth Murray-Clay

TBA

7:30AM Moa Persson

Global coupling between the solar wind and the oxygen ion escape at Venus

7:45AM Carolina Villarreal D’Angelo

The use of Lyman alpha observations to constrain stellar and planetary winds properties

8:00AM Tatsuya Yoshida

Hydrodynamic escape of a reduced proto-atmosphere on Mars

8:15AM Thomas Cravens

Estimates of Photochemical Oxygen Loss Rates from Mars-like Exoplanets

8:30AM Vladimir Airapetian

The Atmospheric Response of Earth-like Exoplanets to X-ray and EUV emission from TRAPPIST1 and TOI-700 M dwarfs

8:45AM All

Discussion

9:00AM All

Break



Tuesday Session 2: Magnetospheres, Reservoirs, and Drivers

Time (MDT) First Author Topic
9:30AM Fran Bagenal

TBA

9:55AM Dimitri Veras

The future evolution of planetary magnetospheres

10:10AM Erdal Yiğit

Thermospheric gravity wave activity during dust storms and influence on escape

10:25AM Judy J. Chebly

Destination exoplanet: Habitability conditions influenced by stellar winds properties

10:40AM Daria Kubyshkina

Atmospheric mass loss through time: concurrent influence of the stellar irradiation and the own planetary environment

10:55AM Suk-Bin Kang

Energetic particle precipitation-driven ionization and heating in the upper atmosphere of magnetized exoplanets around M dwarfs

11:10AM All

Discussion



Wednesday Session 1: Ion Outflow and Escape

Time (MDT) First Author Topic
7:00AM Alex Glocer

Ion escape of primary and secondary atmospheres for Earth and Earth-sized exoplanets

7:25AM Hans Nilsson

Ion escape at Mars and Earth compared

7:40AM Chuanfei Dong

Role of Planetary Obliquity in Regulating Atmospheric Escape: G-dwarf versus M-dwarf Earth-like Exoplanets

7:55AM Naritoshi Kitamura

Limited impact of escaping photoelectrons on the terrestrial polar wind flux in the polar cap

8:10AM Niloufar Nowrouzi

The Variation of Auroral Ionospheric Outflow during ICME and SIR Sawtooth Events

8:25AM Leonardo Regoli

Atmospheric Escape of our Terrestrial Home ExploreR (AETHER)

8:40AM All

Discussion

9:00AM All

BREAK



Wednesday Session 1: Poster Session

Time (MDT) First Author Topic
9:30AM-11:30AM All

Poster Session



Thursday Session 1: Effects of Magnetic Fields on Ion Escape

Time (MDT) First Author Topic
7:00AM Guillaume Gronoff

Atmospheric Escape Processes and Planetary Atmospheric Evolution: from misconceptions to challenges

7:25AM James Green

Magnetospheres of Terrestrial Exoplanets and Exomoons: Implications for Habitability and Detection

7:40AM Romain Maggiolo

Semi-empirical modelling of the effect of planetary magnetization on atmospheric escape for various solar wind pressure levels

7:55AM Tristan Weber

Martian crustal magnetic field influence on ion escape as measured by MAVEN

8:10AM Ryoya Sakata

Dependences of ion escape from ancient Mars on solar wind, solar XUV, and intrinsic magnetic field conditions

8:25AM Yingjuan Ma

The influence of planetary magnetic field on ion escape rate

8:40AM All

Discussion

9:00AM All

BREAK



Thursday Session 2: Planetary Magnetic Fields and their Consequences

Time (MDT) First Author Topic
9:30AM Robin Ramstad

Do Intrinsic Magnetic Fields Protect Atmospheres from Stellar Winds? – Lessons from Ion Measurements at Mars, Venus, and Earth

9:55AM Yaxue Dong

Localized Hybrid Simulation of Martian Crustal Magnetic Cusp Regions

10:10AM Eric G. Blackman

Role of magnetospheres in protecting planetary atmospheres and the connection to stellar activity evolution

10:25AM Marin Anderson

Extrasolar Space Weather Monitoring: Stellar and Planetary Radio Emission as a Probe of Habitability

10:40AM Evgenya Shkolnik

Measuring the Magnetic Fields of Exoplanets with Star-Planet Interactions

10:55AM Nick Schneider

Does exoplanet aurora imply the presence of a global magnetic field?

11:10AM All

Discussion

11:25AM All

Concluding Remarks

Abstracts


Tuesday Session 1: Atmospheric Escape Processes and Drivers


Global coupling between the solar wind and the oxygen ion escape at Venus

Moa Persson, IRAP, CNRS-UPS-CNES, Toulouse, France

Co-authors: Y. Futaana, Swedish Institute of Space Physics, Kiruna, Sweden R. Ramstad, LASP, University of Boulder Colorado, Boulder, CO, USA A. Schillings, Department of Physics, Umeå University, Umeå, Sweden K. Masunaga, LASP, University of Boulder Colorado, Boulder, CO, USA H. Nilsson, Swedish Institute of Space Physics, Kiruna, Sweden A. Fedorov, IRAP UPS CNRS, Toulouse, France S. Barabash, Swedish Institute of Space Physics, Kiruna, Sweden

Understanding the influence of a global magnetic field requires a comparison with the baseline – non-magnetised planets. Venus is a good example because of its lack of both an intrinsic and crustal magnetic fields. An important characteristic for Venus is that today, it has a very dry and thick atmosphere, but that it might have been covered with several hundreds of meters of water on its surface in its early history. One of the mechanisms that could be responsible for the loss of the water is atmospheric escape to space. One of the largest escape channels at Venus at present day is non-thermal ion escape through the magnetotail. The interaction between the solar wind and the Venusian ionosphere causes an energy transfer from the solar wind to the ionospheric particles. When the ionospheric ion reaches above escape energy (~8 eV for O+) it escapes to space. It has been shown that the escape of oxygen ions at Venus increases as the energy in the upstream solar wind increases. In this study, we extend the previous escape study by further investigating how much of the solar wind energy that are transferred to the escaping particles and how the energy transfer changes with the upstream conditions.

We used the Ion Mass Analyser (IMA) sensor, part of the ASPERA-4 instrument package on board Venus Express, to investigate the coupling between the net power of the escaping oxygen ions and that of the upstream solar wind. We show that only about 0.01 % of the available solar wind power is transferred to the escaping ions, and that the percentage decreases as the available energy in the upstream solar wind increases. This means that, today, the Venusian induced magnetosphere is very efficient at protecting its atmosphere from being stripped by the solar wind. A comparison with a similar study made at Mars, which has crustal magnetic fields but no intrinsic magnetic field, shows a similar trend to that at Venus, but the energy transfer from the solar wind to the Martian ionospheric ions is more effective. A similar study at Earth, which has an intrinsic magnetic field, showed a different response of its escape to the variations in the energy of the upstream solar wind, than both Venus and Mars. Here, we will show the coupling between the solar wind and oxygen ion escape for Venus, and compare it with the similar studies made at Mars and Earth.


The use of Lyman alpha observations to constrain stellar and planetary winds properties

Carolina Villarreal D’Angelo, Instituto de Astronomía Teórica y Experimental (IATE)

The amount of high energy irradiation that gaseous planets orbiting very close to their star receive can cause the heating and expansion of their upper atmospheric layers.

If the planetary atmosphere is heated enough, the gas can become gravitationally unbound from the planet and escape in the form of a wind. The wind of these particular exoplanets will interact with the wind from their host star creating signatures that can be observed.

Atmospheric escape has been detected for a couple of hot-Jupiters and warm-Neptunes by means of in-transit spectroscopy observations carried in Lyman alpha line at first. These observations then became a tool to constrain the properties of the planetary and stellar wind using numerical simulations.

In this talk, I will present the results from 3D numerical magneto-hydrodynamic simulations that models the wind-wind interaction in the HD209458 and GJ436 systems. The results from these simulations are used to reproduce the observations in Lyman alpha (and H alpha in the case of GJ436) and constrain the system parameters like the characteristics of the stellar wind or the presence of a planetary magnetic field. I will also discuss the role of the stellar wind, charge exchange and radiation pressure in shaping the neutral material that escape from the planet and produced the line signature.


Hydrodynamic escape of a reduced proto-atmosphere on Mars

Tatsuya Yoshida, Tohoku University

Co-authors: Kiyoshi Kuramoto (Hokkaido University)

Mars may have obtained a proto-atmosphere enriched in H2, CH4, and CO during accretion. Such a reduced proto-atmosphere would have been largely lost by hydrodynamic escape, but its flux is highly uncertain. To estimate the evolution of the proto-atmosphere of Mars correctly, an exact escape modeling including exact radiative balance and chemical processes is required partly because those reduced species and their photochemical products may act as an effective coolant that suppresses the escape of atmosphere. Here we develop a one-dimensional hydrodynamic escape model that includes radiative processes and photochemical processes for a multi-component atmosphere and apply to the reduced proto-atmosphere on Mars.

Under the enhanced XUV flux suggested for young Sun, the escape flux decreases by more than one order of magnitude with increasing the mixing fraction of CH4 and CO from zero to > 10 % mainly because of the energy loss by radiative cooling by these infrared active chemical molecules. Concurrently, the mass fractionation between H2 and other heavier species becomes to be enhanced. Given that the proton-Mars initially obtained > 10 bar of H2 and carbon species equivalent to 1 bar of CO2 was then left behind after the end of the hydrodynamic escape of H2, the total amount of carbon species lost by hydrodynamic escape is estimated to be equivalent to 20 bar of CO2 or more. Such a severe loss of carbon species may explain the paucity of CO2 on Mars compared to Earth and Venus. If the proto-Mars obtained > 100 bar of H2, the timescale for H2 escape exceeds ~100 Myr. This implies that an atmosphere with reduced chemical compositions allowing the production of organic matter deposits may have been kept on early Mars traceable by geologic records.


Estimates of Photochemical Oxygen Loss Rates from Mars-like Exoplanets

Thomas Cravens, University of Kansas

Co-authors: A. Renzaglia (U. Kansas), A. Rahmati (UC Berkeley), O. Hamil (Univ. Kansas), and J. L. Fox (Wright State Univ.)

The evolution of the atmosphere of Mars and the loss of volatiles over the lifetime of the solar system has been a key motivation for the Mars Atmosphere and Volatile Evolution (MAVEN) mission. Studies based on MAVEN data have demonstrated that the major atmospheric oxygen loss process is photochemical – that is, the escape of fast O atoms produced by dissociative of the major ionospheric ion species, O2+. A hot oxygen corona is also produced by this process and some O loss is due to ion loss associated with the solar wind interaction with the planet. Note that at Venus and Earth, all the hot O atoms produced by the dissociative recombination reaction have speeds less than the escape speed and cannot directly escape, although ion loss is possible. Using our Mars-based knowledge, this talk will consider how we can extend our understanding of this key atmospheric loss process to different size Mars-like exoplanets and to different levels of stellar ionizing radiation. The effects of different upper atmosphere compositions will also be discussed. Oxygen loss has direct relevance to the retention of volatiles (whether carbon dioxide or water) by planets, and thus to issue of habitability.


The Atmospheric Response of Earth-like Exoplanets to X-ray and EUV emission from TRAPPIST1 and TOI-700 M dwarfs

Vladimir Airapetian, NASA/GSFC/Sellers Exoplanet Environments Collaboration (SEEC) and American University, DCEEC and American University, DC

Co-authors: Jared M. Bell (NASA/GSFC/SEEC) Alex Glocer (NASA/GSFC/SEEC) Suk-bin Kang (NASA/GSFC/SEEC) William Danchi (NASA/GSFC/SEEC)

Recent Kepler, K2, TESS, HST and ground-based observations suggest that exoplanets around active G-M planet hosts should be exposed to high ionizing radiation fluxes from stellar coronae, flares, magnetized winds and coronal mass ejections. What is the impact of the high-energy radiation on atmospheres of rocky exoplanets? The answer to this question is one of the central issues to exoplanetary habitability, because the presence of a thick high molecular weight atmosphere over sufficiently long timescales is a crucial factor associated with planetary surface pressure and its exposure to stellar UV and particle irradiation. Here we present the results of 1D Exo-GITM models of thermodynamics and atmospheric dynamics of an Earth-like exoplanet controlled by quiescent coronal XUV emission from TRAPPIST-1 and TOI-700. We show that ion escape is the dominant process in atmospheric escape at the XUV flux ~ 1-10 times of the solar flux, which is characteristic of conditions for a recently discovered rocky exoplanet TOI-700d. Our models suggest that the transition from ion escape to hydrodynamic escape occurs at ~ 60 times of the XUV solar flux. We discuss the implications of the atmospheric escape due to XUV driven photoionization driven heating and Joule heating rate for unmagnetized and a magnetized planet and habitability conditions for TOI-700d and TRAPPIST-1a-e rocky exoplanets.




Tuesday Session 2: Magnetospheres, Reservoirs, and Drivers


The future evolution of planetary magnetospheres

Dimitri Veras, University of Warwick

Co-authors: Aline Vidotto (Trinity College Dublin)

How planetary magnetospheres evolve after the Sun turns off of the main sequence has relevant applications for extrasolar planetary systems, particularly with respect to habitability. Here we determine how the size of planetary magnetospheres evolve over time from the end of the main sequence through to the white dwarf phase due to the violent winds of red giant and asymptotic giant branch stars. By using a rough semianalytic prescription, we investigate the entire relevant phase space of planet type, planet orbit and stellar host mass. We find that the planetary magnetosphere will always be quashed at some point during the giant branch phases unless the planet’s magnetic field strength is at least two orders of magnitude higher than Jupiter’s current value. We also show that the time variation of the stellar wind and density does not allow a magnetosphere to be maintained at any time for field strengths less than 10^{−5} T (0.1 G). This lack of protection hints that habitable planets orbiting white dwarfs would have been previously inhospitable.


Thermospheric gravity wave activity during dust storms and influence on escape

Erdal Yiğit, George Mason University

Co-authors: Alexander S. Medvedev, Mehdi Benna, Bruce Jakosky

Atmospheric gravity waves (GWs) of lower atmospheric origin play an important role for the variability and the mean structure of the Martian middle and upper atmosphere, and ionosphere. Lower atmospheric global dust storms affect the Martian weather and variability of the whole Martian atmosphere system as well. Here we present a recent analysis of the CO2 density data from the Neutral Gas and Ion Mass Spectrometer (NGIMS) instrument on board NASA’s Mars Atmosphere Volatile EvolutioN (MAVEN) spacecraft that show a remarkable increase in the GW-induced density fluctuations in the thermosphere during the 2018 major dust storm. The mean thermospheric GW activity increases by a factor of two during the peak phase of the dust storm. The magnitude of the relative density perturbations is around 20% on average and 40% locally. It takes about one and a half months after the onset of the storm for the GW activity to start to decrease gradually. We argue that the enhanced temperature disturbances in the Martian thermosphere can facilitate atmospheric thermal escape. For the first time, we estimate observationally that, for a 20% and 40% GW- induced disturbances, the net increase of Jeans escape flux of hydrogen is a factor of 1.3 and 2, respectively. We provide physical evidence for a GW-induced increase in escape and argue that such an enhanced atmospheric escape during dust storms could have played an important role in the history of Mars.


Destination exoplanet: Habitability conditions influenced by stellar winds properties

Judy J. Chebly, Leibniz institute for astrophysics

Co-authors: Julián D. Alvarado-Gómez [1] Katja Poppenhaeger [1] [2] [1 ]Leibniz Institute for Astrophysics Potsdam An der Sternwarte 16, 14482 Potsdam, Germany. [2] University of Potsdam, Institute of Physics and Astronomy, Karl-Liebknecht-Str. 24/25, 14476 Potsdam-Golm.

Stars interact with their planets through gravitation, radiation, and magnetic fields. While magnetic activity decreases with time reducing associated high-energy phenomena, stellar winds persist throughout the entire stellar evolution. The cumulative effect of stellar winds on exoplanets will dominate over other forms of star-planet interactions. This is crucial for processes such as atmospheric erosion which directly connects with the concept of Habitable Zone planets (HZ) around late-type stars. In order to characterize their influence, we are using one of the most detailed solar models that exist to date (the state-of-the-art Space Weather Modelling Framework) and apply it to the stellar winds domain. In this talk/poster I will summarize the initial results from this investigation, showing how different stellar wind properties are affected by stellar parameters such as the surface magnetic field strength and geometry. These results are used to parametrize the limits for sub-Alfvenic con ditions, which drastically affect the type of stellar wind-exoplanet interactions in a given system. Finally, I will discuss the relevance of these results by considering a possible restriction of the classical HZ, which will consider the expected local stellar wind conditions as a function of the surface magnetic field properties of the planet host.

Atmospheric mass loss through time: concurrent influence of the stellar irradiation and the own planetary environment

Daria Kubyshkina, Trinity College Dublin

Co-authors: Aline Vidotto, Trinity College Dublin

The evolution of the atmospheres of low and intermediate-mass exoplanets is strongly affected by evaporation. However, the dominant source of atmospheric escape, which contributes most to planetary evolution and forms the observed population of exoplanets, is yet debated. The two most prominent drivers of atmospheric mass loss are the own post-formation cooling luminosity of a planet and the stellar irradiation. The effect on planetary evolution from both sources depends on planetary parameters, such as mass and orbital separation, and on the starting conditions after protoplanetary disk dispersal, such as the initial atmospheric mass fraction and post-formation luminosity of a planet. In turn, the atmospheric mass loss driven by high-energy stellar irradiation depends also on the type of the host star and on its past activity (and thus the amount of radiation emitted through its lifetime). The latter can be very different for the first Gyr of the main sequence for stars of similar mass and type.

We will present a comparative study of a range of sub-Neptune-like exoplanets that evolve in various orbits around stars of different masses and different evolutionary histories. As a model of atmospheric evolution, we employ our own framework combining planetary evolution in MESA with the escape prescription of hydrogen-dominated atmospheres based on hydrodynamic modeling. We demonstrate that the final state of a planet depends on the host star properties and planet types. In particular, the differences in stellar evolution paths have a bigger effect on planetary evolution for stars close to solar mass or heavier, while for lower mass stars the initial conditions of a planet appear to be more important. This suggests, that the primary driver of atmospheric escape is not the same for different regions of the planetary/stellar parameter space.


Energetic particle precipitation-driven ionization and heating in the upper atmosphere of magnetized exoplanets around M dwarfs

Suk-Bin Kang, NASA/GSFC/CUA

Co-authors: Alex Glocer (NASA/GSFC), Vladimir Airapetian (NASA/GSFC/American University), Willam Danchi (NASA/GSFC)

Interaction of magnetized winds of active planet hosts with exoplanetary magnetospheres is an important factor of upper atmospheric heating that can contribute to atmospheric escape from close-in exoplanets. This interaction can cause formation of energetic proton and electron precipitation into exoplanetary atmospheres through magnetic reconnection or other wave-particle interactions. These precipitating particles can induce ionization in the upper atmosphere via collisions and subsequent ionization of atmospheric neutrals. The ionization rate is further enhanced by secondary electrons released from the cascade ionization of other neutrals until they get thermalized. Ions produced from such impact ionization with neutrals can escape along the magnetic field lines contributing to atmospheric loss. Importantly, the ionospheric conductivity induced by these particles is essential to regulating the upper atmospheric Joule heating defined by the resistive heating associated with the disparate ion and neutral flows transverse to the magnetic field. The upper atmospheric (ionospheric) conductivity closing magnetospheric current can increase atmospheric temperature through Joule heating and can possibly provide significant pressure leading to a hydrodynamic escape. We note that the ionospheric conductivity for most exoplanet scenarios is poorly constrained resulting in significant uncertainty in global simulations of the magnetosphere-ionosphere-atmosphere interaction. In this presentation, we simulate ions and electrons produced by impact ionization due to energetic proton and electron precipitation in magnetized atmospheres of hot Jupiters and close-in rocky exoplanets around M dwarfs. We calculate ionospheric conductivity and show that ionization rates and associated Joule heating rates at the night side due to energetic ion and precipitation can be comparable to X-ray and Extreme UV (XUV) driven photoionization and radiative heating at the day side. This suggests that energetic particle precipitation via stellar wind-magnetosphere processes can potentially drive a substantial atmospheric escape from close-in exoplanets around active stars.



Wednesday Session 1: Ion Outflow and Escape


Ion escape of primary and secondary atmospheres for Earth and Earth-sized exoplanets

Alex Glocer, NASA/GSFC

Co-authors: L. Daldorf, S-B Kang, V. Airapetian, J. Bell, W. Danchi, K. Garcia-Sage – (NASA/GSFC)

Atmospheric escape represents one of the major factors in determining the habitability of a planet, and thus its characterization is required to understand where life can be found. Atmospheric escape is comprised of a myriad of processes including hydrodynamic escape, photochemical escape, ion outflow, Jeans escape, and more. Each of these processes envision a different mechanism by which energy input in the form of stellar wind and Extreme UV flux (EUV) from the planet’s host star can be transformed into energy which can help atmospheric particles overcome gravity and be lost to space. In this presentation we will focus on ion escape at Earth and Earth-sized exoplanets in different regimes. We begin by examining how ion outflow responds to different energy inputs for present day earth. This examination will explore how ion outflow scales with different energy inputs, how this scaling varies by species, and what controls the maximum and minimum values. We will then look at similar escape processes for a close-in Earth-like planet located in the habitable zones of K and M-dwarf stars. In this regime the EUV energy input is much larger and the corresponding ion outflow also increases. Finally, we examine how long an Earth-sized planet can hold on to its partially ionized primary hydrogen atmosphere accreted from the protoplanetary disk under different EUV energy inputs. This study differs from the prior studies discussed in two important ways. First, the primary atmosphere is H dominated instead of oxygenated like the secondary atmosphere. Second, the dominant loss process is hydrodynamic escape including both neutrals and ions as opposed to pure ion outflow. We show in our simulations how long it would take to evacuate the primary atmosphere under different assumptions about energy input from the host star.


Ion escape at Mars and Earth compared

Hans Nilsson, Swedish Institute of Space Physics

Co-authors: Audrey Scillings, Mats Holmström, Stas Barabash, Gabriella Stenberg Wieser, Yoshifumi Futaana

We present ion outflow data from Mars Express IMA spanning more than one solar cycle. We discuss the dependence of the outflow rate on the solar cycle and compare with data from the strong solar maximum of the Phobos mission. We then proceed to compare this with the ion outflow observed at Earth using the Cluster spacecraft. We discuss the similarities, differences and the role of the geomagnetic field of Earth. We highlight the role of ionospheric convection bringing fresh plasma into the outflow region of magnetised planets, and show some Incoherent Scatter radar data of what the initial up flow looks like.


Role of Planetary Obliquity in Regulating Atmospheric Escape: G-dwarf versus M-dwarf Earth-like Exoplanets

Chuanfei Dong, Princeton University

Co-authors: Zhenguang Huang (University of Michigan), Manasvi Lingam (Florida Institute of Technology)

We present a three-species (H+, O+ and e−) multi-fluid magnetohydrodynamic model, endowed with the requisite upper-atmospheric chemistry, that is capable of accurately quantifying the magnitude of oxygen ion losses from “Earth-like” exoplanets in habitable zones, whose magnetic and rotational axes are roughly coincidental with one another. We apply this model to investigate the role of planetary obliquity in regulating atmospheric losses from a magnetic perspective. For Earth-like exoplanets orbiting solar-type stars, we demonstrate that the dependence of the total atmospheric ion loss rate on the planetary (magnetic) obliquity is relatively weak; the escape rates are found to vary between 2.19 × 10^26 s^−1 to 2.37 × 10^26 s^−1. In contrast, the obliquity can influence the atmospheric escape rate (~10^28 s^−1) by more than a factor of 2 (or 200%) in the case of Earth-like exoplanets orbiting late-type M-dwarfs. Thus, our simulations indicate that planetary obliquity may play a weak-to-moderate role insofar as the retention of an atmosphere (necessary for surface habitability) is concerned.


Limited impact of escaping photoelectrons on the terrestrial polar wind flux in the polar cap

Naritoshi Kitamura, Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo

Co-authors: Kanako Seki, (Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo), Yukitoshi Nishimura (Department of Electrical and Computer Engineering and Center for Space Physics, Boston University), and James P. McFadden (Space Science Laboratory, University of California, Berkeley)

A statistical analysis using a long-term (over one solar cycle) photoelectron data set obtained by the Fast Auroral SnapshoT satellite demonstrates that photoelectron outflows has little impact on the polar wind ion flux. This result implies that it is the source region of H+ ions in the topside ionosphere and not the photoelectron flux that controls the terrestrial polar wind flux. The polar wind ion flux, estimated from electron outflow does not change with increasing net photoelectron production due to increasing solar activity. The magnitude of a self-created field-aligned potential drop is likely determined so as to equilibrate electron fluxes with ion fluxes regulated by a net production rate of H+ ions. The result suggests that the polar wind H+ ion flux from magnetized terrestrial planets, including Earth-like exoplanets, can be estimated once the composition and temperature of its atmosphere, which determine the net ion production rate, are known.


The Variation of Auroral Ionospheric Outflow during ICME and SIR Sawtooth Events

Niloufar Nowrouzi, University of New Hampshire

Co-authors: Lynn. M. Kistler (UNH), Eric. J. Lund (UNH), Kai Zhao (NUIST)

Sawtooth events are repeated injections of energetic particles at geosynchronous orbit. Although studies have shown that 94% of sawtooth events occur during magnetic storm times, the main factor that causes a sawtooth event is unknown. Simulations have suggested that heavy ions like O+ may play a role in driving the sawtooth mode by increasing the magnetotail pressure and causing the magnetic tail to stretch. O+ ions located in the nightside auroral region have a direct access to the near-earth plasma-sheet. O+ in the dayside cusp can reach to the midtail plasma-sheet when the convection velocity is sufficiently strong. Whether the dayside or nightside source is more important is not known. We show results of a statistical study of the variation of the O+ and H+ outflow flux during sawtooth events for SIR and ICME sawtooth events. We perform a superposed epoch analysis of the ion outflow using the TEAMS (Time-of-Flight Energy Angle Mass Spectrograph) instrument on the FAST spacecraft. TEAMS measures the ion composition over the energy range of 10 eV e-1 to 12 keV e-1. We have done major corrections and calibrations (producing 3D data set, anode calibration, mass classification, removing ram effect and incorporating dead time corrections, potential correction) on TEAMS data and produced a data set for four data species (H+, O+, and He+). From 1996 to 2007, we have data for 108 orbits of CME-driven and for 83 orbits of SIR-driven sawtooth events with an altitude above 1500 km. We will compare the outflow at different local times before and after substorm onset, and for CME and SIR storms


Atmospheric Escape of our Terrestrial Home ExploreR (AETHER)

Leonardo Regoli, Johns Hopkins University Applied Physics Laboratory

Co-authors: Pontus Brandt (JHU/APL), Matina Gkioulidou (JHU/APL), Ian Cohen (JHU/APL), Abigail Rymer (JHU/APL), Peter Kollmann (JHU/APL), Angelos Vourlidas (JHU/APL), Romina Nikoukar (JHU/APL), Robert Lillis (SSL/UCB), Mike Chaffin (LASP/CU-B), Raluca Ilie (UIllinois), Iannis Dandouras (IRAP/CNRS), Mats Andre (IRF), Mats Holmstrom (IRF), Keika Kunihiro (UTokyo), Kanako Seki (UTokyo), David Brain (LASP/CU-B), Orenthal Tucker (GSFC), Tom Nordheim (JPL)

The presence of an atmosphere is thought to be one of the fundamental criteria for sustaining a habitable environment. Earth, Mars and Venus belong to the habitable zone, with very different evolution of their atmospheres and climates. Until recently, it was commonly believed that the presence of an intrinsic magnetic field helped shield a planetary atmosphere by standing off the solar wind and preventing its direct interaction with the upper atmosphere. However, present-day estimates of escape rates for the three planets are very similar, despite Earth, in contrast to Mars and Venus, having an intrinsic magnetic field. The scattered estimates of current terrestrial escape rates fall in a very wide range from below the current loss rates of Mars and Venus up to two orders of magnitude above.

The Atmospheric Escape of our Terrestrial Home ExploreR (AETHER) will provide the necessary measurements to address its overarching science goal:

“Understand global terrestrial atmospheric loss to space as an example of a magnetized planet in the habitable zone”

AETHER will achieve this goal by providing the most accurate escape rates of both neutral and ionized particles from the Earth under a range of upstream conditions, thus providing an insight into the role of the global geomagnetic field in protecting the Earth’s atmosphere.

With this mission, we will provide the scientific community the necessary dataset to further understand the evolution of the terrestrial atmosphere in particular, and of other terrestrial planets in general.



Wednesday Session 2: Poster Abstracts are at the bottom of this page.



Thursday Session 1: Effects of Magnetic Fields on Ion Escape


Atmospheric Escape Processes and Planetary Atmospheric Evolution: from misconceptions to challenges

Guillaume Gronoff, SSAI / NASA LaRC

Co-authors: Arras, P. (University of Virginia, Charlottesville, VA); Baraka, S. (NIA, Hampton, VA); Bell, J. (NASA GSFC, Greenbelt, MD); Cessateur, G. (BIRA/IASB, Brussels, Belgium); Cohen, O. (University of Massachussetts, Lowell, ME); Curry, S. (Space Science Laboratory, Berkeley, CA); Drake, J. (Center for Astrophysics, Cambridge, ME); Elrod, M. (NASA GSFC, Greenbelt, MD); Erwin, J. (BIRA/IASB, Brussels, Belgium); Garcia-Sage, K. (NASA GSFC, Greenbelt, MD); Garraffo, C. (Center for Astrophysics, cambridge, MD); Glocer, A. (NASA GSFC, Greenbelt, MD); Heavens, N. (Space Science Institute, Boulder, CO); Lovato, K. (Hampton University, Hampton, VA); Maggiolo, R. (BIRA/IASB, Brussels, Belgium); Parkinson, C. (Space Science Institute, boulder, CO); Simon Wedlund, C. (IWF, Graz, Austria); Weimer, D. R. (NIA, Hampton, VA); Moore, W. B. (NIA, Hampton, VA)

The recent discoveries of telluric exoplanets in the habitable zone of different stars have led to questioning the nature of their atmosphere, which is required to determine their habitability. Atmospheric escape is one of the challenging problems to be solved: simply adapting what is currently observed in the solar system is doomed to fail due to the large variations in the conditions encountered around other stars. A better strategy is to evaluate the different processes that shaped planetary atmosphere and to evaluate their importance depending upon the stellar conditions.

We reviewed the different escape mechanisms and their magnitude in function of different conditions [Gronoff et al. 2020]. This led us to discuss the importance of a magnetic field in protecting an atmosphere. The importance of the thermal escape, of polar wind, and of the transport of plasma within the magnetosphere are typically forgotten when claiming that magnetic fields are protecting planetary atmospheres and leading to their habitability.

Overall, the habitability of a planet should not be claimed only on by its location in the habitable zone but also after careful analysis of the interaction between its atmosphere and its parent star .

Gronoff, G., Arras, P., Baraka, S., Bell, J. M., Cessateur, G., Cohen, O., et al. ( 2020). Atmospheric Escape Processes and Planetary Atmospheric Evolution. Journal of Geophysical Research: Space Physics, 125, e2019JA027639. https://doi.org/10.1029/2019JA027639


Magnetospheres of Terrestrial Exoplanets and Exomoons: Implications for Habitability and Detection

James Green, NASA Headquarters

Co-authors: Scott Boardsen, Goddard Space Flight Center and Chuanfei Dong, Princeton University

The ravaging of planetary atmospheres in young solar systems due to extreme solar radiation and particle fluxes is believed to be a significant factor for our understanding of how an exoplanet will develop and maintain an atmosphere, which is a critical element of a habitable environment. Meanwhile, recent studies show that planetary magnetic fields may protect planets from atmospheric losses indicating planetary magnetic fields play an important role in planetary habitability.

Another factor that should be considered with respect to the habitability of a terrestrial exoplanet concerns the magnetic characteristics of an associated exomoon. With the existence of exoplanets well established, one of the next frontiers is the discovery of exomoons. Despite all reported identification of exomoon candidates are still controversial, efforts have been made to search for exomoons and understand their formation during the past years. Since it is without a doubt that they must exist around some exoplanets, it is important to examine what role, if any, they would have in creating an environment that contributes to the habitability of their host planet.

Although speculated for several decades, only recently have scientists determined that our Moon had an extensive magnetosphere for several hundred million years soon after it was formed. We have investigated the expected magnetic topology of the early Earth-Moon magnetospheres and found that they would couple in such a way as to protect the atmosphere of both the Earth and Moon. By extension of this technique, we show the results of our magnetic field topological modeling which demonstrate that terrestrial exoplanet-exomoon coupled magnetospheres work together to protect the early atmospheres of both the exoplanet and the exomoon. When exomoon magnetospheres are within the exoplanet’s magnetospheric cavity, the exomoon magnetosphere acts like a protective magnetic bubble providing an additional magnetopause confronting the stellar winds when the moon is on the dayside. In addition, magnetic reconnection would create a critical pathway for the atmosphere exchange between the early exoplanet and exomoon. When the exomoon’s magnetosphere is outside of the exoplanet’s magnetosphere it then becomes the first line of defense against strong stellar winds, reducing exoplanet’s atmospheric loss to space.


Semi-empirical modelling of the effect of planetary magnetization on atmospheric escape for various solar wind pressure levels

Romain Maggiolo, royal Belgian Institute for Space Aeronomy, Belgium

Co-authors: Herbert Gunell, Umeå University, Sweden Gael Cessateur, royal Belgian Institute for Space Aeronomy, Belgium Johan De Keyser, royal Belgian Institute for Space Aeronomy, Belgium Justin T. Erwin, royal Belgian Institute for Space Aeronomy, Belgium Vivianne Pierrard, royal Belgian Institute for Space Aeronomy, Belgium Fabien Darrouzet, royal Belgian Institute for Space Aeronomy, Belgium Maria Hamrin, Umeå University, Sweden

Gunell et al. (2018, doi:10.1051/0004-6361/201832934) developed a semi empirical model of atmospheric escape describing the dependence of the atmospheric escape rate on planetary magnetic field strength for Venus-, Earth- and Mars-like planets. This model is based on in-situ measurements of atmospheric escape that are scaled as a function of the planetary magnetic moment using physical considerations and a magnetic field model. The model shows that the escape rate is not a monotonic function of the planetary magnetic moment but rather shows multiple peaks over a wide range of magnetizations because the escape rates for different escape mechanisms peak at different values of the magnetic moment; this is particularly true for escape of ions through the polar caps and for escape through the cusps. We present a new version of this model that includes a dependency on the solar wind dynamic pressure. Considering the influence of solar wind pressure on atmospheric escape is a first step to better characterize the effect of planetary magnetic fields on the past atmospheric erosion of rocky planets when the Sun was more active.


Martian crustal magnetic field influence on ion escape as measured by MAVEN

Tristan Weber, NASA Goddard Space Flight Center

Co-authors: Tristan Weber, David Brain, Shaosui Xu, David Mitchell, Jared Espley, James McFadden Gael Cessateur, royal Belgian Institute for Space Aeronomy, Belgium Johan De Keyser, royal Belgian Institute for Space Aeronomy, Belgium Justin T. Erwin, royal Belgian Institute for Space Aeronomy, Belgium Vivianne Pierrard, royal Belgian Institute for Space Aeronomy, Belgium Fabien Darrouzet, royal Belgian Institute for Space Aeronomy, Belgium Maria Hamrin, Umeå University, Sweden

The martian surface is scattered with pockets of magnetism that were left in place by the planet’s former dynamo. In some locations, crustal magnetic fields act as “mini-magnetospheres”, shielding the planet’s atmosphere, while in other locations they act as channels for enhanced energy input and particle escape. The net effect of this system is not intuitively clear, but previous modeling studies have suggested that crustal fields likely decrease global ion escape from Mars. In this study we use data from the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft to analyze how crustal magnetic fields influence both global and local ion escape at Mars. We find that crustal fields only increase ion escape if ions are not bound tightly to the magnetic field. Specifically, ion escape is increased only if closed magnetic fields trap 35% or less of energized Oxygen ions. In any other case, crustal fields decrease both global and local ion escape by as much as 40% and 80%, respectively. This suggests that the presence of crustal magnetic fields has had a moderate impact on atmospheric ion loss throughout Martian history, potentially influencing the planet’s atmospheric evolution and habitability.


Dependences of ion escape from ancient Mars on solar wind, solar XUV, and intrinsic magnetic field conditions

Ryoya Sakata, The University of Tokyo

Co-authors: K. Seki [1], S. Sakai [2], N. Terada [2], H. Shinagawa [3], T. Tanaka [3,4] ([1] Graduate School of Science, The University of Tokyo [2] Graduate School of Science, Tohoku University [3] National Institute of Information and Communications [4] International Center for Space Weather Science and Education, Kyushu University)

https://drive.google.com/open?id=1lGGPkXksKM-0sJfKqwke-XsZxfnLbDmZ


The influence of planetary magnetic field on ion escape rate

Yingjuan Ma, UCLA

Co-authors: Chris Russell, Gabor Toth; Andrew Nagy, Dave Brain

The influence of planetary magnetic field strength on ion escape rate is evaluated using a multi-species MHD model of Mars under different IMF orientations and solar cycle conditions with current Mars atmosphere. To examine the effect of planetary magnetic field, we run a set of simulation cases with identical solar wind parameters but different planetary magnetic field strengths ranging from 0 to 5000 nT. Model results clearly show that the detailed relationship between ion escape rates and planetary dipole strength depends on the IMF orientations as well as ionospheric thermal pressure controlled by solar EUV flux. In general, we found that the total ion escape rate does not vary much for weakly magnetized cases (< 50 nT) and increases for intermediate planetary dipole cases (100 nT-500nT). Model results for relative strong planetary dipole cases may require extra caution, as kinetic processes are neglected in the MHD model calculation.



Thursday Session 2: Planetary Magnetic Fields and their Consequences


Do Intrinsic Magnetic Fields Protect Atmospheres from Stellar Winds? – Lessons from Ion Measurements at Mars, Venus, and Earth

Robin Ramstad, Laboratory for Atmospheric and Space Physics / University of Colorado Boulder

Co-authors: Stas Barabash – Swedish Institute of Space Physics

Recent studies of atmospheric ion escape rates at Mars, Venus, and Earth have enabled a direct comparison between the planets, revealing mutually different dependencies on upstream solar wind and solar extreme ultraviolet (EUV) conditions. We describe a general framework for understanding ion escape as a process that can be limited by potential bottlenecks, such as ion supply, solar wind energy transfer, and transport efficiency, effectively determining the state of the ion escape process at each planet. We find that ion escape from Venus and Earth is energy-limited, though exhibit differing dependencies on solar wind and EUV, revealing the influence of Earth’s intrinsic magnetic field on coupling between outflowing ions and the solar wind. In contrast, ion escape from Mars is in a supply-limited state, mainly due to its low gravity, and has likely contributed relatively little to the total loss of the early Martian atmosphere, in comparison to neutral escape processes. Contrary to the current paradigm, the comparisons between these terrestrial planets in the solar system indicate that an intrinsic magnetic dipole field may either decrease or increase the escape rate, depending on the upstream conditions. We argue that a modern, nuanced, and evidence-based view of the magnetic field’s role in atmospheric escape is required to understand the evolution of planetary atmospheres.


Localized Hybrid Simulation of Martian Crustal Magnetic Cusp Regions

Yaxue Dong, University of Colorado

Co-authors: Brain, David (Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, USA); Jarvinen, Riku (Department of Electronics and Nanoengineering, Aalto University, Aalto, Finland; Finnish Meteorological Institute, Helsinki, Finland); Egan, Hilary; Poppe, Andrew (Space Sciences Lab, University of California, Berkeley, CA, USA)

Mars does not have a global dipole magnetic field, but has localized crustal fields, which play a role in the ionosphere and solar wind interaction. The Martian crustal fields are involved in various physical processes in the induced magnetosphere, such as particle precipitation, field-aligned currents, and ion outflow. These processes usually occur in the magnetic ‘cusp’ regions with mostly vertically aligned and open field lines. Due to the small spatial scale of the Martian crustal magnetic cusps, localized models with high spatial resolutions and ion kinetics are needed to understand the physical processes in the cusp regions.

We use the HYB hybrid simulation platform developed at the Finnish Meteorological Institute to model Martian magnetic cusp regions. We adapt the HYB model to a moderately strong magnetic cusp (surface magnetic field strength ~100 nT) on the nightside of Mars. Two plasma sources are included in the simulation: hot protons from the magnetotail and cold heavy ions from the ionosphere. Our model results can qualitatively reproduce the vertical electric potential drop, particle transport, and field aligned current in the cusp region, which provides a possible mechanism of the buildup of the vertical electric field and the energy transfer between the two plasma populations. We also run the model under different ionosphere and magnetic field conditions to study the variability of the cusp system and discuss the effects on the ion escape in the cusp region.


Role of magnetospheres in protecting planetary atmospheres and the connection to stellar activity evolution

Eric G. Blackman, University of Rochester

Co-authors: John A. Tarduno

Although a magnetosphere always provides some protection from the effects of stellar radiation, the extent to which it protects against stellar wind ablation depends upon (1) how well it deflects wind mass, energy, and momentum and (2) how well it traps otherwise escaping plasma. Using an analytic approach to highlight key concepts, we estimate mass, energy, and momentum capture rates for magnetized vs. unmagnetized planet and use them to constrain upper limits on mass loss. The approach reveals a competition between local reduction of incoming plasma flux by a planetary magnetic field and an increase in capture area. Distinguishing whether the dominant threat is input energy or momentum is also important. If the ionopause or magnetopause is close to the planet surface, as for Venus and Mars, wind momentum is likely most damaging. For planets with large magnetospheres, like Earth, energy is more likely the problem. This combination of factors can conspire to produce similar mass loss rates for planets of different magnetizations. When coupled to models of stellar activity evolution, we find that Earth’s magnetosphere actually captured actually more mass but less energy than it would have if unmagnetized since start of the geodynamo. However, as the solar wind weakens in the future and the magnetospheric capture area increases, local focusing of incoming charged particles toward the magnetic poles may increase even the local energy flux beyond that of an unmagnetized planet. This highlights that the longer term protective role of Earth’s magnetic field, and for planetary magnetospheres generally, crucially depends on their ability to trap outgoing plasma.


Extrasolar Space Weather Monitoring: Stellar and Planetary Radio Emission as a Probe of Habitability

Marin Anderson, Jet Propulsion Laboratory, California Institute of Technology

Both stellar magnetic activity — transient mass loss events like coronal mass ejections (CMEs) and stellar energetic particles (SEPs) — and exoplanet magnetospheres play an important role in defining habitability. Radio observations provide a unique window to both phenomena, and have been well-studied in our own solar system, from solar radio bursts associated with space weather events like CMEs and SEPs, to auroral radio emission from all the magnetized bodies in the solar system.The relevance of planetary magnetic fields to atmospheric retention and, consequently, habitability, remains an important open question. Detection of exoplanet magnetic fields and atmospheres would provide a large and diverse sample of objects outside our solar system with which to examine this question. Similarly, radio observations of a large and diverse sample of nearby stars are critical for understanding stellar space weather environments – especially the prevalence of CMEs on other stars, about which very little is currently known. I will present ongoing work with the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA), a low-frequency radio array that is pioneering the concept of extrasolar space weather monitoring and targeting exoplanet magnetospheres. I will conclude by looking towards the future of radio observations of stars and exoplanets with next-generation, space-based radio arrays.


Measuring the Magnetic Fields of Exoplanets with Star-Planet Interactions

Evgenya Shkolnik, Arizona State University

Planets interact with their host stars through gravity, radiation and magnetic fields. For giant planets orbiting stars within ~20 stellar radii (=0.1 AU for a Sun-like star), magnetic star-planet interactions (SPI) are observable at a range of wavelengths with a variety of photometric, spectroscopic and spectropolarimetric techniques. At such close distances, planets orbit within the sub-alfvénic radius of the star, where magnetic interactions are particularly efficient, allowing for the detection and study of exoplanetary magnetic fields, thus probing their internal dynamics and atmospheric evolution. In this talk, I will provide a review (and preview) of magnetic SPI studies for hot Jupiters orbiting Sun-like stars. As we refine our observational techniques, we can extend them to lower-mass stars where the sub-alfvénic region coincides with the classical habitable zone, giving us a way with future experiments to detect the magnetic fields of potentially habitable planets.


Does exoplanet aurora imply the presence of a global magnetic field?

Nick Schneider, LASP, U. Colorado

Co-authors: Sonal Jain, Zac Milby, Justin Deighan, LASP/U. Colorado

The key question “Is a global magnetic field required for exoplanet habitability?” compels the followup “How can we detect a global magnetic field?”. A plausible answer is that planets with global magnetic fields have auroral activity (e.g., Hallinan et al., 2015). This is exemplified by the Earth and Jupiter, the terrestrial and jovian planets with the strongest magnetic fields having the greatest auroral activity. What’s less known is that Mars, lacking a global magnetic field, has recently been shown to have extensive global aurora enabled by the lack of a global magnetic field. The same is probably true for Venus (Phillips et al. 1986, Slanger et al. 2001, Gray et al., 2014). Evidence for Mars’ global aurora comes from the Imaging UltraViolet Spectrograph on the MAVEN mission orbiting Mars. Space weather events even during solar minimum conditions have led to planet-engulfing ultraviolet aurora (Schneider et al., 2018) from the penetration of ~100 keV electrons deep into the atmosphere. The episode was accompanied by “ground level event”” hazardous radiation measured by Curiosity’s RAD instrument (Hassler et al., 2018) with direct reliance to habitability.

The existence of aurora on an unmagnetized planet does not invalidate the general correlation with global magnetic fields, but it demands a closer look. A key difference between aurora on Mars vs. Earth/Jupiter is where the energy is derived. Is derived locally at the planet, for example by particle acceleration through reconnection in a global field, as for Earth and Jupiter? Or at the star/Sun in space weather events, as dominates at Mars? This difference in where the precipitating particles are accelerated can affect the associated planetary emissions. Ultraviolet and visible emissions are relatively insensitive to the source of energy, since the emission is generated within the atmosphere where precipitation occurs. Radio emissions, often generated in the acceleration process, are more strongly correlated with a planetary global magnetic field. The takeaway messages are that the presence or absence of aurora emissions cannot be construed as evidence for or against a global magnetic fields, and a deeper investigation is called for into which detections would constitute valid evidence.



Wednesday Session 2: Poster Abstracts


Learnings from the Paleo-Magnetosphere: Global Simulations of a Geomagnetic Excursion using Historic Rock Magnetism Records

Agnit Mukhopadhyay, University of Michigan

https://drive.google.com/open?id=19rUMV752kwRFEPV54pFtKC5_DRjzS8Ip


Thermal escape in Earth-like terrestrial exoplanets and early Earth with intense XUV environments

Akifumi Nakayama, The University of Tokyo

The retention of the atmosphere is known to a key factor for planetary climates and habitability. For instance, the atmospheric mass diverse the planetary climate of a terrestrial exoplanet included the young Earth into warm or cold climate, even planets in the habitable zone. While terrestrial planets inside the habitable zone are commonly exposed to the high-energy X-ray and ultraviolet (XUV) photons irradiated by host stars. In particular, low-temperature late dwarfs have a longer active phase than Sun-like stars, although planets around late dwarfs are promising targets for near-future atmospheric characterization. The previous studies suggest that XUV intensities of active young Sun and other active stars are enough to erode the present Earth-like atmosphere in a short term. Previous theoretical studies of the thermosphere structure and atmospheric thermal escape for terrestrial atmospheres mainly focused on the energy balance between heating via irradiated XUV and cooling via molecular IR radiation of vibrational-rotational transitions and hydrodynamical effects. However, their models would lack an important cooling process in the high-temperature gas. The cooling by atomic line emission, which is caused by the transition of electronic states, is known to a common process in several astronomical fields at high temperature, such as hydrogen Lyman cooling in hot Jupiter atmosphere and line emissions of hydrogen and metals in molecular clouds. So far, we have a poor understanding of how such process behaves in high XUV intensity and Earth-like N$_2$-O$_2$ atmosphere, corresponding to the young Earth and terrestrial exoplanets in the habitable zone. To do so, we revisit the response of the upper atmospheric structure for N$_2$-O$_2$ atmosphere in Earth-mass planet to an elevated level of XUV intensity, using a newly developed upper atmosphere model. The model presented here includes thermo- and photo-chemistry, thermo- and chemical diffusion, hydrodynamics, absorption of stellar IR radiation, and molecular IR radiative cooling as well as other theoretical models and newly consider radiative cooling effect via the electronic transition of atomic species. We find that atomic radiative cooling is efficient before the hydrodynamic effect becomes superior. Atomic radiative cooling becomes the dominant cooling process for the condition where the temperature at the exobase is larger than approximately 3000K. Furthermore, the temperature at the exobase for intense XUV case is regulated to approximately 6000K and insensitive to XUV flux. This is because the cooling efficiency of atomic radiation strongly depends on the temperature in such high temperatures. As a consequence, the upper atmosphere is almost hydrostatic and the atmospheric escape remains sluggish even XUV intensity is comparable to thousand times Earth’s XUV intensity or very active young Sun and planets in the habitable zone orbiting active late dwarfs. The results would give new insights into Earth’s evolution and habitability of terrestrial exoplanets.


Timing of the martian dynamo

Anna Mittelholz, ETH Zurich

The question of how a dynamo field affects atmospheric escape is still widely debated. Any modelling of atmospheric escape thus begs the question about the timing of planetary dynamos. Recent findings regarding the longevity of the martian dynamo using MAVEN magnetic field data indicate an active dynamo field during earliest crustal formation (4.5 Ga), and also while water was active on the martian surface (3.7 Ga). These results, and previous information on the timing of the dynamo need to be considered in models for the integrated atmospheric loss at Mars.


Martian Crustal Field Modifications in the Dayside Ionosphere

Antonio Renzaglia, University of Kansas

Crustal magnetic fields were first discovered at Mars by the Mars Global Surveyor (MGS) mission (Acuña et al., 1998). Since then, there have been several crustal field models and maps produced, as well as many missions to Mars to better study the crustal fields. The crustal fields are thought to influence ion loss from the planet, so having a precise understanding of the structure of these fields is vital. The Mars Atmospheric and Volatile EvolutioN (MAVEN) explorer is yet another mission to the red planet, and its magnetometer (MAG) instrument has been returning interesting data on both induced and crustal fields. Induced magnetic fields are the result of the solar wind interaction with the Martian ionosphere, in areas where crustal fields are less strong. Sometimes, a current sheet is formed when these 2 types of fields are found in close proximity to one another. Cravens et al. (2020) and Harada et al. (2017) considered cases in which magnetic reconnection took place in these current sheets. But what was not explored in these papers is that the currents in the boundary will not just affect the external induced field regions, but will affect the crustal field regions as well. We discuss this “extended” interaction and consider what can be learned from the perturbation of the crustal magnetic field in the dayside ionosphere, and also how these interactions may affect atmospheric loss from the planet.


Solar wind forcing of planetary environments in the presence and absence of intrinsic magnetospheres

Arnab Basak, Center of Excellence in Space Sciences India, IISER Kolkata

An intrinsic planetary magnetosphere provides shielding against the impinging solar wind particles, thereby reducing atmospheric erosion. When a planet loses its global magnetic field due to the halting of its interior dynamo, the solar wind is able to penetrate closer to the planetary surface leading to greater atmospheric loss and impacting the planetary habitability. The imposed magnetosphere which forms around the planet due to the draping solar magnetic field is not as effective in protecting the atmosphere. The entire mechanism of such complex dynamics is reproduced by 3D compressible magnetohydrodynamic simulations using the Star Planet Interaction Module (CESSI-SPIM) developed at CESSI, IISER Kolkata. Planets with gravitationally stratified atmospheres and hosting magnetospheres of varying dipole strengths are considered for comparison. We also simulate a case analogous to the conditions of present-day Mars by considering a non-magnetized planet without atmosphere. The results are found to be in agreement with observations from Mars Global Surveyor (MGS) and Mars Atmosphere and Volatile EvolutioN (MAVEN) missions and is expected to complement data from the recent Mars missions. The study is relevant for the exploration and detection of habitable planets in solar and exoplanetary systems. References: (1) A. Basak and D. Nandy, MNRAS 502, 3569 (2021).


Investigating the 2007 global scale dust storm at Mars with ASPERA-3

Catherine Regan, Mullard Space Science Laboratory- UCL

In July 2007, a regional dust storm on Mars grew and became global, engulfing the entire planet and lasting several months. This storm had a profound impact across Mars, with dust reaching altitudes of 80 km and global temperatures rising by up to 40 K. It is seen from Mars Express (MEx) MARSIS data that ionization created in the lower atmosphere is observed at higher altitudes, with an altitude dependent enhancement in plasma density over crustal magnetic fields (Venkateswara et al., 2019). The Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) experiment on the MEx spacecraft has operated at Mars since 2004 (continuing to operate today) and has produced a long time-base of plasma measurements from as low as 250 km. ASPERA-3 on MEx will be used to investigate the effects the 2007 global dust storm had on the plasma environment by comparing data before, during, and after the event. Of particular interest are plasma measurements over radial magnetic fields from crustal anomalies, where transport of charged particles is guided out of the atmosphere. The before, during, and after effects will shed light on to the influence dust storms have on the escaping plasma measured by ASPERA-3 and how dust changes the local plasma escape directly from the atmosphere. Our initial study focuses on data from the electron spectrometer (ELS) where we investigate how the energy distribution and peak energy value varies in altitude above the Martian surface.


Modeling the impact of stellar XUV radiation and energetic charged particles on atmospheric escape and planetary habitability

Dimitra Atri, New York University in Abu Dhabi

Stellar XUV radiation and energetic charged particles impact planetary atmospheres by inducing atmospheric escape, changes in chemistry and enhancing biological radiation dose on the surface. These effects can significantly impact planetary habitability. We use the Flare Frequency Distribution (FFD) of stars observed by Transiting Exoplanet Survey Satellite (TESS) to calculate atmospheric escape rates of potentially habitable planets through the hydrodynamic escape channel. We compare the integrated loss of planetary atmospheres from flares and steady state stellar XUV around FGKM stars over 5 billion years and discuss its impact on their potential habitability. We also model how stellar particle events interact with exoplanetary magnetospheres and enhance radiation dose on their surfaces. Finally, we discuss studying these phenomena in greater detail on Mars using MAVEN data.


Geomagnetic storms effect on foF2 of ionosphere at mid lattitude

Dr. Shivangi Bhardwaj, Sri Sai University, Palampur, Himachal Pradesh, India

We have studied the effect of geomagnetic storms on critical frequency of F2 layer i.e. foF2 of ionosphere. We have chosen mid latitude station, Guangzhou (23.1N, 113.4E). To characterize the state of ionosphere over the selected station we have used the ground based ionosonde observations. We considered nine geomagnetic storms that occurred during the peak of solar cycle 23. From our analysis we found that during the geomagnetic storms a significant decrease occurs in the value of foF2.


Reconstructing the Extreme Ultraviolet Emission of Cool Dwarfs

Girish M. Duvvuri, CU Boulder/CASA/LASP

Characterizing the atmospheres of planets orbiting M dwarfs requires understanding the spectral energy distributions of M dwarfs over planetary lifetimes. Surveys like MUSCLES, HAZMAT, and FUMES have collected multiwavelength spectra across the spectral type’s range of effective temperature and activity, but the extreme ultraviolet flux (EUV, 100 to 912 Angstroms) of most of these stars remains unobserved because of obscuration by the interstellar medium compounded with limited detector sensitivity. While targets with observable EUV flux exist, there is no currently operational facility observing between 150 and 912 Angstroms. Inferring the spectra of exoplanet hosts in this regime is critical to studying the evolution of planetary atmospheres because the EUV heats the top of the thermosphere and drives atmospheric escape. Here we present our implementation of the differential emission measure (DEM) technique to reconstruct the EUV spectra of cool dwarfs with uncertainties characterized by applying our method to the Sun and AU Mic. We demonstrate preliminary DEM models and the generated EUV spectra for a larger sample of cool dwarfs and lay the foundation for an interpolation scheme to reconstruct the EUV spectrum of any cool dwarf based on its stellar properties.


Effect of Stellar Coronal Mass Ejection (CME) and Flare on the atmosphere of hot Jupiter HD189733b and its transit signature

Gopal Hazra, Trinity College Dublin

The evolution of planetary atmospheres is very much dependent on the environment of their host stars (e.g., stellar radiation,stellar wind, stellar flares and Coronal Mass Ejections (CMEs)). For close in planets, the stellar radiation evaporates the planetary atmosphere as a form of supersonic planetary outflow due to photoionisation. The interaction of stellar wind with this planetary outflow helps to shape up the atmosphere and its mass loss rate. Moreover, flares and CMEs from the star will also have great impact on planetary evaporation. In this work, we investigate the impact of flares and CMEs on the atmosphere of the exoplanetHD189733b. We solve mass, momentum and energy equations in 3D including ionisation rate equations to launch the planetary outflow self-consistently. As we solve extra photoionisation equations, we can calculate the hydrogen ionisation fraction properly.We study four cases: first – the quiescent phase of the star including stellar wind, second- a flare case, third- a CME case and Fourth- the flare is followed by a CME. We calculate transit lines for each case. We find that the flare case and CME case have asignificant effect on mass loss rate of the planet and hence on its transit lines


Atmospheric escape on oxygenated Earth-like exoplanets and possible observational states

Greg Cooke, University of Leeds

How the upper atmosphere corresponds to the lower atmosphere and surface conditions is a difficult observational problem when characterising rocky exoplanets. Using the 3D Earth System Model WACCM6 (CESM2), we simulate various oxygen levels on Earth, modelling the atmospheric evolution between the start of the Proterozoic geological eon 2.4 billion years ago and present day. We demonstrate how changing oxygen and ozone concentrations modify the atmospheric structure and chemical state of Earth through time, extending the implications to possible exoplanet analogues. Lower oxygen levels reduce hydrogen escape, with fewer O and H atoms, and more N atoms, reaching the thermosphere and ionosphere. For transmission spectra, higher oxygen concentrations result in a more detectable atmosphere, and we predict how to avoid biosignature false negatives (where the detection of the presence of life is missed) on these exoplanets. Our results have implications for exoplanet atmospheric escape, atmospheric redox evolution, and future atmospheric characterisation with next generation telescopes.


Ion streaming instability and solitary structures associated with escaping planetary ions at Mars

Hassan Akbari, NASA GSFC

We present results, obtained by several wave and particle instruments onboard MAVEN, that establish the presence of intense plasma wave activity in conjunction with the initial stage of planetary ion energization inside the Martian induced magnetosphere. The plasma waves are observed over a broad frequency range that extends from below the lower-hybrid frequency (~10 Hz) to the vicinity of the electron cyclotron (~ kHz) and ion plasma frequencies (~kHz). High-resolution electric field burst memory data, furthermore, show the presence of large-amplitude solitary structures, including uni-polar electric field features that likely contain net parallel potential. It is argued that the plasma waves and the nonlinear structures effectively couple the flowing solar wind and the Martian plasma, leading to exchange of energy and momentum and consequently acceleration and loss of planetary O+ and O2+ ions. Similar instabilities are sometimes observed in the F region of the Earth’s auroral ionosphere in conjunction with ion up flow.


Multi-species analysis of perturbation component in the thermosphere and ionosphere on Mars to identify the possible sources

Hiromu Nakagawa, Tohoku University

Large-amplitude perturbations of density and temperature ubiquitously exist in the Martian mesosphere and thermosphere (Bougher et al., 2015; Yigit et al., 2015; Terada et al., 2017; England et al., 2017; Nakagawa et al., 2020), ionosphere (Mayyassi et al., 2019). However, the excitation sources are still open question. There are two possible sources to drive the perturbations: (1) atmospheric waves propagating from lower atmosphere, and (2) energy injected from above by external forcing, such as solar wind, and solar energetic particle. In order to constrain the possible sources to drive perturbations for understanding the regional coupling between lower, upper atmosphere, ionosphere, and space environment at a non-magnetized planet, Mars, we focus on the multi-species analysis of perturbation component of density in the thermosphere and ionosphere by MAVEN/NGIMS. We applied MAVEN/NGIMS dataset at NASA PDS level-2, version-8, revision-1 during the period from February 2015 to 2020 for five years. The perturbation component of neutrals (CO2,N2) and ions (O2+,CO2+,O+) are identified by the polynomial fit to the individual profile (residual from the fit), as similarly done by England et al. (2017) and Mayyassi et al. (2019). Local-time dependence is most significant in the thermospheric perturbations, as suggested by Terade et al. (2017) and Nakagawa et al. (2020). Annual variation of the amplitudes from year to year is also noteworthy. We found a good correlation of perturbation amplitudes between CO2 and N2 in both dayside and nightside over the five years. This result suggests lower atmospheric waves in the long-wavelength limit is the main candidate for the thermospheric perturbations in nightside, in addition to dayside (Cui et al., 2014; England et al., 2017). Meanwhile, anti-correlation of perturbation amplitudes between CO2+ and O+ can be seen only in dayside. This result suggests photochemical “imprint” in dayside ionosphere indicates the strong thermosphere-ionosphere coupling in dayside. Good correlation of perturbation amplitudes between CO2 and CO2+ in dayside supports this fact. On the other hand, Less or positive correlation of perturbation amplitudes between CO2+ and O+ in nightside implies that the external sources mainly drive the nightside perturbations in the ionosphere which contradict those originated from below. In addition, we have investigated the role of the crustal magnetic field on the atmospheric coupling in dayside. We found no significant difference in the thermospheric perturbations between northern and southern hemisphere. This suggests that the crustal magnetic field does not affect on the lower-upper atmospheric coupling. We also found the notable ion-specific perturbations especially in southern hemisphere, in addition to the moderate correlation between CO2 and CO2+. This is consistent with Mayyassi et al. (2019); which suggests that the crustal magnetic field might disturb the thermosphere-ionosphere coupling, possibly due to the injected particles along the magnetic field from the space. Further study is needed to investigate the SEP-induced perturbation and its mechanism.


The Disconnect between UV and White-Light Flares in Low-Mass Stars

James A. G. Jackman, Arizona State University

Stellar flares are explosive phenomena that release radiation across the entire electromagnetic spectrum. The far-UV emission from flares can dissociate atmospheric species and exacerbate atmospheric erosion. Yet, the near-UV flux may be necessary for the emergence of life on rocky planets around low-mass stars such as TRAPPIST-1. A detailed knowledge of the UV energies and rates of flares is therefore essential for our understanding of the habitability of M dwarf systems. However, measurements of UV flare rates require expensive campaigns with HST, meaning habitability studies instead often use UV rates based on extrapolations from white-light studies with TESS. Despite their use in contemporary habitability studies, such extrapolations are untested and their accuracy remains unconstrained. To this end, we have combined TESS white-light and archival GALEX UV photometry for M dwarfs from TESS cycles 1 to 3 to test the UV predictions of habitability studies. We will show how white-light flare studies underestimate the UV rates of flares, how to correct for this effect, and the impact our results have on our current understanding of the UV environments of exoplanets around M dwarfs.


Seasonal dependency of exospheric loss due to photoionization at Mercury

Jamie Jasinski, NASA Jet Propulsion Laboratory, California Institute of Technology.

We present the first investigation and quantification of the photoionization loss process to Mercury’s sodium exosphere from spacecraft and ground‐based observations. We analyze plasma and neutral sodium measurements from NASA’s MESSENGER spacecraft and the THEMIS telescope. We find that the sodium ion (Na+) content and therefore the significance of photoionization varies with Mercury’s orbit around the Sun (i.e., true anomaly angle: TAA). Na+ production is affected by the neutral sodium solar‐radiation acceleration loss process. More Na+ was measured on the inbound leg of Mercury’s orbit at 180°–360° TAA because less neutral sodium is lost downtail from radiation acceleration. Calculations using results from observations show that the photoionization loss process removes ∼10^24 atoms/s from the sodium exosphere, showing that modeling efforts underestimate this loss process. This is an important result as it shows that photoionization is a significant loss process and larger than loss from radiation acceleration. Despite planetary differences in heliocentric distance, space environment processes, and atmospheric content, the estimated loss of sodium due to photoionization at Mercury is similar to ion loss rates at Venus and Mars.


Detection of Young Stars and a Brown Dwarf at Low Radio Frequencies

Jason Ling, Rice University

Detection of low-frequency (<5 GHz) radio emission from stellar and planetary systems can lead to new insights into stellar activity, extra-solar space weather, and planetary magnetic fields, as stellar emissions are often associated with Type II and III radio bursts and planetary emissions are typically due to the cyclotron maser instability [CMI], mediated through the planetary magnetic field. In this work, we investigate 3 large field-of-view surveys at 74 MHz, 150 MHz, and 1.4 GHz, as well as a myriad of multi-wavelength ancillary data, to search for radio emission from about 2600 stellar objects, including about 800 exoplanetary systems, 600 nearby low-mass stars, and 1200 young stellar objects located in the Taurus and Upper Scorpius star forming regions. We report 11 detections at 1.4 GHz, 6 of which also have corresponding 150 MHz signals. Notably, all 11 radio sources are located in nearby star forming regions, and one appears to be a young brown dwarf. Our results enlarge the number of pre-main sequence stars observed at frequencies of 1.4 GHz or less by a factor of 3. Furthermore, we use image stacking and statistical methods to derive upper limits on the average quiescent radio luminosity of the family of objects under investigation. These analyses provide observational constraints for large-scale searches for low-frequency radio emissions from stars and planets.


HoME: Habitability of Magnetized Environments

Julián D. Alvarado-Gómez, Leibniz institute for astrophysics

The stellar magnetic field completely dominates the environment around late-type stars. It is responsible for driving the coronal high-energy radiation (EUV/X-rays), the development of stellar winds, and the generation transient events such as flares and coronal mass ejections (CMEs). These elements can have a strong impact in the evolution of planetary systems via star-planet interactions and erosion of exoplanetary atmospheres, making them a critical aspect to be considered in our search for habitable places in the Universe. In this context, the project “HoME: Habitability of Magnetized Environments” aims to perform a systematic characterization on how stellar magnetism affects the habitability conditions of exoplanetary systems and determine how such conditions change across spectral type and age. To achieve this objective, HoME employs surface magnetic field distributions of stars, in the form of Zeeman-Doppler Imaging (ZDI) observations and/or from high-end dynamo simulations, to construct physics-based models of the environments around stars and exoplanets. An example of the HoME characterization for the Proxima Centauri system is summarized in this poster contribution.


Dependences of H+ and O+ Outflows from the Dayside Cusp Region and the Nightside Aurora: a comparison study

Kai Zhao, Nanjing University of Information Science and Technology

Recalibrated FAST/Time-of-Flight Energy, Angle, and Mass Spectrograph (TEAMS) data is used to investigate the correlations between the H+ and O+ outflows from both the dayside cusp region and the nightside auroral oval zone and the parameters related to energy input to the Earth’s ionosphere. The data is collected during the 24 – 25 September 1998 geomagnetic storm following a coronal mass ejection (CME) event. Those parameters include the Alfvénic Poynting flux (Sac) associated with waves at frequencies from 0.125 to 0.5 Hz, the quasistatic Poynting flux (Sdc) measuring the fluctuations with frequencies below 0.125 Hz, the omni-directional number flux of electrons (fen), the omni-directional energy flux of the electrons (fee), the density of electrons in the loss cone (nep), and the amplitude of the extreme low frequency (ELF) waves at frequencies from 30 Hz to 20 kHz (AELF). The Poynting flux is calculated as EV×δBwest/μ0, thus indicates the input electromagnetic energy to the iono


Effects of crustal magnetic fields on the atmospheric ion escape from Mars observed by MAVEN

Kanako Seki, University of Tokyo

https://drive.google.com/open?id=1fQ_ZALPsfoawLUsc2ZKJrg9l76kr0nBA


A two-spacecraft study of Mars’ induced magnetosphere’s response to upstream conditions

Katerina Stergiopoulou, Swedish Institute of Space Physics (IRF), Uppsala, Sweden

The solar wind input to the Martian system plays a decisive role in formulating the morphology of the near-Mars plasma environment. Ion escape rates, boundary locations around the planet and the structure of the induced magnetosphere in general, have been shown by numerous studies to be influenced by the upstream solar wind conditions. This work is a two spacecraft study in which we investigate the effects of the upstream solar wind conditions on the Martian induced magnetosphere. We use Mars Express (MEX) magnetic field magnitude data from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument together with interplanetary magnetic field (IMF) measurements, solar wind density and velocity from the magnetometer (MAG) and the Solar Wind Ion Analyzer (SWIA) instruments on board Mars Atmosphere and Volatile EvolutioN (MAVEN), from November 2014 to November 2018. We make real time comparisons of the IMF magnitude and the magnetic field magnitude in the induced magnetosphere of Mars, and we test the ratio B_{MEX}/B_{MAVEN} against the solar wind dynamic pressure, speed and density. The response of the induced magnetosphere to intervals of higher than the average solar wind dynamic pressure leads to the enhancement of the induced fields especially on the dayside. However, when the induced fields are analysed relative to instantaneous values of IMF, by calculating the ratio B_{MEX}/B_{MAVEN}, a different picture emerges particularly when examining the response of this quantity to factors such as the solar wind dynamic pressure, solar wind density and speed. We find enhanced relative induced fields mainly on the dayside and up to the nominal magnetic pile-up boundary region, for lower than the average solar wind dynamic pressure.

Despite the stronger magnetic fields observed in the induced magnetosphere during periods of high solar wind dynamic pressure, when we compare these fields with the interplanetary magnetic field (IMF) measured simultaneously, we see in fact relative enhancements for low solar wind dynamic pressure. In the tail, the induced or draped fields rise appreciably at the terminator, likely indicative of the more dynamic aspects of the Martian induced magnetotail, and suggesting that the fields observed in the tail are not purely those of the draped IMF. We again observe relatively higher values in the tail of the ratio of induced (local) fields to the upstream IMF for intervals of lower upstream dynamic pressure, thus following the same trend observed on the dayside. Dividing the solar wind dynamic pressure into its components, we notice that the patterns seen in solar wind density resemble the behaviour observed in the solar wind dynamic pressure cases, thus at least tentatively suggesting that the upstream density has a larger controlling influence on the structure of the induced magnetosphere than the solar wind velocity does.

Enhanced upstream dynamic pressure is responsible for enhanced

induced fields and increased atmospheric escape. However, some caution should be taken in describing such dependencies, since the induced fields themselves are conversely more significantly enhanced relative to the IMF during intervals of lower dynamic pressure. This conclusion is generally in agreement with results reported earlier by Ramstad et al. (2017) [Ramstad et al., (2017), Global Mars-solar wind coupling and ion escape, Journal of Geophysical Research: Space Physics, 122], where is shown that the efficiency of atmospheric escape is inversely related to the solar wind dynamic pressure. Obtaining a clearer picture of the configuration of the ionosphere and the induced magnetosphere is necessary for complete understanding the processes driving ion escape.


MHD Effects of the Stellar Wind on Observations of Escaping Exoplanet Atmospheres

Laura Harbach, Imperial College London

Interaction with the stellar wind and accompanying radiation can result in significant atmospheric erosion, potentially affecting a planet’s ability to host life. Previous research indicates the atmospheres of close-in, low-mass planets are highly vulnerable to the effects of XUV driven photoevaporation. However, the effects of the stellar wind on low-mass exoplanet atmospheres have only just begun to be addressed. We present 3D magnetohydrodynamical (MHD) simulations of the effect of the stellar wind on the escaping atmosphere of a magnetized planet in the habitable zone of a low-mass M dwarf. We use the TRAPPIST-1 system as the basis of our simulations and model the planet to have an H-rich evaporating outflow, with a pre-defined mass loss rate. Our results show the atmospheric outflow is dragged and accelerated upon interaction with the stellar wind, resulting in a diverse range of planetary magnetospheres which are strongly dependent on the local stellar wind conditions through the orbit and can vary over timescales as short as an hour. We explore the implications of this wind-outflow interaction on potential observations of escaping atmospheres and show that stellar wind interactions provide an explanation for observed variations in transit absorption features.


Cassini observations of ionospheric plasma in Saturn’s magnetosphere

Marianna Felici, Boston University

It is well known that the ionosphere is an important mass source for the magnetosphere at Earth, but lesser attention has been dedicated to study the ionospheric mass source at Saturn.

Felici et al. (2016) presented evidence of ionospheric outflow from Saturn’s ionosphere, detected when Cassini was located at ≃ 2200 h Saturn local time, 36 RS far from Saturn. During several entries into the magnetotail lobe, tailward flowing cold ions were observed; the ions appeared to be dispersed in energy and the Ion Mass Spectrometer/Time Of Flight instrument revealed a ion composition dominated by light ions. Ultraviolet auroral observations showed a bright and extended aurora, and the heliospheric model ENLIL suggested that the magnetosphere was being compressed by a region of high solar wind dynamic pressure. Felici et al. (2016) considered several configurations for the active atmospheric regions and estimated the corresponding source and mass rates outflowing the ionosphere.

We have now identified 247 instances in the Cassini Plasma Spectrometer Singles (CAPS/SNG) data, in which the ions appear dispersed in energy. For two of these events, we conducted an investigation of the location of the spacecraft in respect to the plasma sheet, flow direction, ion composition, ionospheric and solar wind activity at the times of detections, utilizing the Cassini Magnetometer data, CAPS Time of Flight data, Cassini Ultraviolet Imaging Spectrograph data, and ENLIL model results. We interpreted these additional events as ionospheric outflow, estimated the number flux, and lastly, compared these results to the estimates by Felici et al. (2016) and the models for ionospheric outflow at Saturn presented in Glocer et al. (2007) and Martin et al. (2020).

We will present these new results that show ionospheric outflow events with different characteristics and number fluxes, underlining the variability of this phenomenon and its importance for improving our understanding of ionosphere-magnetosphere coupling, the ionosphere as a source of plasma for the magnetosphere, how much upstream conditions drive the system, and extrapolating ionospheric escape rate at Saturn.

References

Felici, M., Arridge, C. S., Coates, A. J., Badman, S. V., Dougherty, M. K., Jackman, C. M., Kurth, W. S., Melin, H., Mitchell, D. G., Reisenfeld, D. B., et al. (2016), Cassini observations of ionospheric plasma in Saturn’s magnetotail lobes, J. Geophys. Res. Space Physics, 121, 338– 357, doi:10.1002/2015JA021648.

Glocer, A., T. I. Gombosi, G. Toth, K. C. Hansen, A. J. Ridley, and A. Nagy (2007), Polar wind outflow model: Saturn results, Journal of Geophysical Research: Space Physics, 112 (A1), doi:10.1029/2006JA011755.

Martin, C. J., Ray, L. C., Felici, M., Constable, D. A., Lorch, C. T. S., Kinrade, J., Gray, R. L. (2020), The effect of field-aligned currents and centrifugal forces on ionospheric outflow at Saturn, Journal of Geophysical Research: Space Physics, 125 (e2019JA027728), doi:10.1029/2019JA027728.


Using an enhanced spacecraft wake to detect escaping ionospheric ions

Mats André, Swedish Institute of Space Physics, Uppsala, Sweden

Much of the ionospheric escape from Earth is in the form of cold (eV) positive ions with a low energy (few eV) supersonic drift. These ions can not reach a spacecraft charged to tens of volts, but rather cause an enhanced wake. We have developed a method to use Cluster spacecraft observations of this wake to estimate the flux of escaping ions to about 10^26 ions/s which is a significant fraction of the total outflow. Can this method be used on other missions and around other planets?


Estimating Ion Escape from Unmagnetized Planets

Mats Holmstrom, Swedish Institute of Space Physics

We present a new method to estimate ion escape from unmagnetized planets that combines observations and models. Assuming that upstream solar wind conditions are known, a computer model of the interaction between the solar wind and the planet is executed for different ionospheric ion production rates.

This enables studies of how escape depend on different parameters, and also escape rates during extreme solar wind conditions, applicable to studies of escape in the early solar system, and at exoplanets.


Terrestrial Ionospheric Ions Observed at Lunar Orbit

Matthew Fillingim, Space Sciences Laboratory, University of California, Berkeley

During its orbit about Earth, the Moon spends about one week per month in the terrestrial magnetotail. Lunar orbiting spacecraft, then, can measure escaping ions as the ions travel down the magnetotail past the Moon. Two such spacecraft, the Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS) probes, have observed multiple instances of outflowing heavy ions presumably of ionospheric origin at the Moon. The heavy ion fluxes, which are observed during geomagnetically disturbed times, consist of atomic and molecular species traveling at nearly identical velocities as the concurrently observed protons. Backwards particle tracing in time-dependent electromagnetic fields derived from magnetohydrodynamic models of the terrestrial magnetosphere suggests that these ions originate in the near equatorial inner magnetosphere, escape the inner magnetosphere through magnetopause shadowing near noon, and are subsequently accelerated to common velocities down the low‐latitude boundary layer to lunar distances. Terrestrial ionospheric outflow is often considered a high latitude process involving the polar wind or auroral heating mechanisms. These results highlight the role of the dayside inner magnetosphere and magnetopause region may play in escape processes. Changes in magnetospheric convection and/or movement of the dayside magnetopause (intrinsic or induced) due to changes in external drivers (IMF and solar wind dynamic pressure) may be an important process contributing to escape. The HERMES instrument suite on the upcoming Lunar Gateway will be an ideal platform from which to measure ionospheric escape down the terrestrial magnetotail and to constrain the processes and pathways leading to escape.


Seasonal and dust related variations of the dayside thermospheric and ionospheric compositions of Mars observed by MAVEN/NGIMS

Nao Yoshida, Tohoku University

We report seasonal and dust related variations of neutral and ion species (CO2, O, and N2, and CO2+, O2+, O+, and N+) in the dayside Martian upper atmosphere between ~150 and 250 km altitudes observed by the Neutral Gas and Ion Mass Spectrometer aboard the Mars Atmosphere and Volatile Evolution spacecraft. We find that major ions, O2+, O+, and CO2+ in the ionosphere vary mainly according to the seasonal variation of CO2 density in the thermosphere. The sinusoidal seasonal variations of CO2+ and O2+ densities are clearly identified, while that of O+ is less discernible. These observed seasonal variations of ion densities are well reproduced by a photochemical equilibrium model. Furthermore, we find a decrease in O, O+, and O2+ densities in the whole altitude range at Ls = 342 – 346 in MY 33 during a regional dust event. The decrease in O density would lead to the decrease in O+ and O2+ densities in the ionosphere through ion-neutral reactions. Observed variations of ion and neutral species associated with season and a regional dust storm are also confirmed in pressure coordinates. Observations show that O2+/O+ and CO2+/O+ ratios at a given pressure level in the ionosphere vary by a factor of up to ~3, which can modify the composition of escape ion flux from the Martian atmosphere.


Solar zenith angle dependence of relationships between energy inputs to the ionosphere and ion outflow fluxes

Naritoshi Kitamura, Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo

The ionosphere is one of the important sources for magnetospheric plasma, particularly for heavy ions with low charge states. We investigate the effect of solar illumination on the number flux of ion outflow using data obtained by the Fast Auroral SnapshoT satellite at 3000–4150 km altitude from 7 January 1998 to 5 February 1999. We derive empirical formulas between energy inputs and outflowing ion number fluxes for various solar zenith angle ranges. We found that the outflowing ion number flux under sunlit conditions increases more steeply with increasing electron density in the loss cone or with increasing precipitating electron density (>50 eV), compared with the ion flux under dark conditions. Under ionospheric dark conditions, weak electron precipitation can drive ion outflow with small averaged fluxes (~10^7 cm^−2 s^−1). The slopes of relations between the DC and Alfvén Poynting fluxes and outflowing ion number fluxes show no clear dependence on solar zenith angle. Intense ion outflow events (>10^8 cm^−2 s^−1) occur mostly under sunlit conditions (solar zenith angle < 90°). Thus, it is presumably difficult to drive intense ion outflows under dark conditions, because of a lack of the solar illumination (low ionospheric density and/or small scale height owing to low plasma temperature).


Observations of Ion Upflow in Conjunction with Pulsating Aurora

Niharika Godbole, University of New Hampshire

Pulsating aurora is a commonly observed phenomenon that occurs in the post-midnight sector. Near magnetic midnight on March 3rd, 2014, the e-POP satellite traversed a region of pulsating aurora over eastern Canada. In-situ data suggest a Type II ion upflow event which occurred in coincidence with the pulsating aurora. Features in this event are similar to those recorded by ground-based All-Sky Imagers and PFISR on February 7th, 2017, which show signatures of Type II ion upflow alongside pulsating aurora. Data from both events are presented and analyzed.


Small-scale magnetic structure in the Martian ionosphere

Oliver Hamil, University of Kansas

Charactarization of small-scale magnetic structure morphology using MAVEN data. Various magnetic structures exist in the martian ionosphere, including magnetic slabs, flux-ropes, rotated ionopause-type structures, etc. How these structures are formed is not well established. One possible explanation for the magnetic structures is variation in the upstream IMF in which small scale timing stuctures in the solar wind are “frozen in” at the top of the ionosphere and subsequently convected downward in altitude and outward to higher solar zenith angle. We seek to identify various structure morphologies and establish whether they have any connection to the upstream solar wind. Such a connection, if it exists, may be important to ionospheric dynamics and relevant to atmospheric loss at Mars. This knowledge may further our understanding of the interaction between a Mars-like exoplanet and its parent star.


Planet-induced radio emission from the coronae of M dwarfs

Robert Kavanagh, Trinity College Dublin

There have recently been detections of radio emission from low-mass stars, some of which are indicative of star-planet interactions. Motivated by these exciting new results, here we present stellar wind models for the two active planet-hosting M dwarfs Prox Cen and AU Mic. Our models incorporate large-scale photospheric magnetic field maps, reconstructed using the Zeeman-Doppler Imaging method. We use our models to assess if planet-induced radio emission could be generated in the coronae of the host stars, through a mechanism analogous to the sub-Alfvénic Jupiter-Io interaction. For Prox Cen, we do not find any feasible scenario where the planet can induce radio emission in the star’s corona, as the planet orbits too far from the star in the super-Alfvénic regime. However, in the case that AU Mic has a mass-loss rate of 27 times that of the Sun, we find that both planets b and c in the system can induce radio emission from 10 MHz – 3 GHz in the corona of the host star for the majority of their orbits, with peak flux densities of 10 mJy. Our predicted emission bears a striking similarity to that recently reported from GJ 1151, which is indicative of being induced by a planet. Detection of such radio emission would allow us to place an upper limit on the mass-loss rate of the star, and also constrain the magnetic field strength of the planet that induces the emission.


Escape of planetary ions from Mercury’s magnetosphere under different solar wind conditions

Sae AIZAWA, IRAP

The combination of Mercury’s weak intrinsic magnetic field and solar wind conditions at Mercury’s location results in the formation of a relatively small magnetosphere compared to that of Earth. Typical bowshock and magnetopause locations at Mercury are 2 and 1.4 Mercury radius from the center of Mercury, respectively, and thus, Mercury’s mini-magnetosphere is strongly compressed and may disappear when solar wind condition is extreme. Under these particular circumstances, the solar wind can directly interact with its exosphere and surface and planetary ion escape is expected to be enhanced. In this study, the production and escape of planetary ions from the exosphere have been investigated under different solar wind conditions using the global hybrid simulation LatHyS. In particular, we have focused on dynamic pressure and interplanetary magnetic field dependence. This study will provide a good indication of the ability of a mini-magnetosphere to protect its exosphere from ion escape, to be compared to that of the larger magnetosphere of the Earth.


Effects of the IMF direction on atmospheric escape from a Mars-like planet under weak intrinsic magnetic field conditions

Shotaro Sakai, Tohoku University

The relationship between planetary climate change and the existence of intrinsic magnetic fields is an interesting research topic. It is considered that Mars had maintained a warm and wet climate until ~4 billion years ago. However, the atmosphere and water were lost, resulting in only a thin Martian atmosphere. A recent model study suggests that Mars lost a large portion of the atmosphere within 500 million years of its origin. One of the important processes of atmospheric escape is ion outflow from the Martian upper atmosphere, which is useful for the escape of heavy species such as ionospheric ions. The escape mechanism due to ion outflow strongly depends on the solar wind parameters, solar X-ray and extreme ultraviolet (XUV) irradiances, and magnetic field conditions.

Direction of the upstream interplanetary magnetic field (IMF) also significantly changes the magnetospheric configuration, influencing the atmospheric escape mechanism. This paper investigates effects of IMF on the ion escape mechanism from a Mars-like planet that has a weak dipole magnetic field directing northward on the equatorial surface. The northward (parallel to the dipole at subsolar), southward (antiparallel), and Parker-spiral IMFs under present solar wind conditions are compared based on multispecies magnetohydrodynamics simulations. In the northward IMF case, molecular ions escape from the high-latitude lobe reconnection region, where ionospheric ions are transported upward along open field lines. Atomic oxygen ions originating either in the ionosphere or oxygen corona escape through a broader ring-shaped region. In the southward IMF case, the escape flux of heavy ions increases significantly and has peaks around the equatorial dawn and dusk flanks. The draped IMF can penetrate into the subsolar ionosphere by erosion, and the IMF becomes mass-loaded as it is transported through the dayside ionosphere. The mass-loaded draped IMF is carried to the tail, contributing to ion escape. The escape channels in the northward and southward IMF cases are different from those in the Parker-spiral IMF case. The escape rate is the lowest in the northward IMF case and comparable in the Parker-spiral and southward IMF cases. In the northward IMF case, a weak intrinsic dipole forms a magnetosphere configuration similar to that of Earth, quenching the escape rate, while the Parker-spiral and southward IMFs cause reconnection and erosion, promoting ion escape from the upper atmosphere.


Star-planet interactions in Close-in Exoplanets: high energy irradiation versus strong stellar winds

Stephen Carolan, Trinity College Dublin

The high-energy flux in X-ray and Extreme ultraviolet that young close-in planets receive from their host stars can lead to strong atmospheric evaporation. For these planets, their atmospheres take the form of dense photoevaporative hydrogen outflows. The stellar wind exerts pressure on the expanding atmosphere and, if sufficiently strong, can affect atmospheric escape rates and spectroscopic transit signatures. We study the dichotomy of the escaping atmosphere in these close-in systems. The high EUV stellar flux they receive is expected to cause strong atmospheric escape. However the stellar wind, particularly for young stars, can be very strong which could reduce or even inhibit the planet’s atmospheric escape. Through 3D hydrodynamic simulations, we show that, as the stellar wind becomes stronger, the evaporation rates of close-in exoplanets are reduced and their atmospheres are forced to occupy a smaller volume. This affects Ly-α transit signatures, which are reduced to barely any absorption in the extreme stellar wind scenario. Future Ly-α transits could therefore place constraints not only on the evaporation rate of of these planets, but also on the mass-loss rates of their host stars.

I will also present here our newly developed 3d radiation magnetohydrodynamic models, where we simulate the local environment of a magnetised Hot Jupiter, investigating how the atmospheric escape rate and star-planet interaction are affected, for a variety the planet’s magnetic field strength.


Study of atmospheric ion escape from exoplanet TOI-700 d based on multi-species MHD simulation.

Tomoaki Nishioka, Graduate School of Science, University of Tokyo

https://drive.google.com/open?id=1D4i3YAwMYjx__9Fyf-pppRJxUMj1DEVL

Atmospheric escape from the Earth during geomagnetic reversal

Tsareva Olga, Atmospheric escape from the Earth during geomagnetic reversal

The magnetosphere protects the planetary atmosphere from erosion by the solar wind. The question arises as to what will happen to the atmosphere during the geomagnetic reversal, when the dipole component weakens. Atmospheric erosion models are generalized to the case of a dipole-quadrupole magnetosphere. It is shown how the ion escape rates change depending on the configuration and strength of the geomagnetic field during the reversal.


Atomic oxygen loss during proton auroral events at Mars

Valery I. Shematovich, Institute of Astronomy of the Russian Academy of Sciences

Proton auroral events are observed in the dayside atmosphere of Mars and are caused by the high-energy hydrogen atom fluxes (ENA-H) penetrating into the neutral atmosphere (Deighan et al., 2018). Such events also cause the loss of neutral atomic oxygen from the Martian atmosphere. The processes of formation, kinetics, and transport of suprathermal oxygen atoms in the transition region (from the thermosphere to the exosphere) during proton auroral events at Mars were considered. An additional source of hot oxygen atoms – momentum transfer collisions of the precipitating high-energy H atoms with atomic oxygen in the upper atmosphere of Mars, namely, QOh: H(E) + Oth  H(E’ < E) + Osth(E""=E-E') - was taken into account in the Boltzmann kinetic equation for suprathermal O atoms, which was solved using the Monte Carlo kinetic model (Shematovich, Kalinicheva, 2020). As a result, the estimates of the hot oxygen population in the Martian corona were obtained and it was shown that proton auroral events are accompanied by atmospheric loss of the atomic oxygen with value varying in the range (3.5-5.8) ×107 cm-2s-1. The calculated values of the atmospheric loss rate of oxygen atoms caused by the ENA-H precipitation during proton auroral events on Mars are comparable to the values of the atmospheric O loss due to photochemistry (Groeller et al., 2014; Jakosky et al., 2018). It should be noted that although the proton auroras at Mars are sporadic events, the escaping flux of the suprathermal oxygen atoms induced by the precipitation processes can become even dominant under conditions of extreme solar events - solar flares and coronal mass ejections-as it was found in the recent observations of the MAVEN spacecraft (Jakosky et al., 2018). It seems that the loss of the Martian atmosphere due to the forcing by the solar wind plasma and, in particular, the precipitation of high-energy proton and hydrogen atom fluxes during solar flares may play an important role in the atmospheric loss on astronomical time scales (Shematovich, Bisikalo, 2021).

Deighan J., Jain S. K., Chaffin M. S., …, and Jakosky B. M. Discovery of a proton aurora at Mars. Nature Astronomy. 2018. V. 2. P. 802-807.

Shematovich V. I., Kalinicheva E.S. Atmospheric escape of oxygen atoms during the proton aurorae at Mars. Astronomy Reports. 2020. V. 64. P. 628–635

Groeller H., Lichtenegger H., Lammer H., Shematovich V. I. Hot Oxygen and Carbon Escape from the Martian Atmosphere. Planet. Space Sci. 2014. V. 98, P. 93-105.

Jakosky B.M., Brain D., Chaffin M., …, Zurek R. Loss of the Martian atmosphere to space: Present-day loss rates determined from MAVEN observations and integrated loss through time. Icarus. 2018. V. 315. P. 146-160.

Shematovich V., Bisikalo D. (2021, February 23). Hot planetary coronas. In Oxford Research Encyclopedia of Planetary Science. Oxford University Press, 2021.


Literature Review: Simulated Ion Escape of Mars, Venus, and Earth

Wenyi Sun, UCLA

As an important part of planetary atmosphere evolution, ion escape has a significant influence on the habitability of planets. Ion escape is affected by solar EUV intensity and upstream plasma flow properties, including solar wind dynamic pressure, interplanetary magnetic field, , etc. Different atmospheric chemical compositions and internal planetary magnetic fields make each planet’s ion escape show its own characteristics. For more than 30 years, many types of models have been developed to study the ion escape of planets, from 1D models to 3D models, from test particle models to MHD and hybrid models. We reviewed the ion escape simulation results of Mars, Venus, and Earth over the past 30 years, summarized their dependences on upstream properties, showed the differences between different models, and compared the results with the observations.


Exosphere of Proxima Centauri B – Photochemical escape from exoplanets

Yuni Lee, UMBC/NASA GSFC

Exoplanets orbiting around M-dwarf are exposed to more extreme stellar environments than our Solar System bodies experience, which can significantly impact the atmospheres of the planets and affect their habitability and sustainability. This study provides the first prediction of volatile loss from the secondary atmosphere of a Mars-like/Venus-like rocky planet based on coupled interaction between planetary plasma and neutral atmosphere in 3D. We have simulated the 3D exosphere of Proxima Centauri b (PCb) based on the ionosphere simulated by a 3D multi-species MHD model. The study is designed to help us understand the star and planet interaction, formation of the exosphere with given atmospheric conditions and resulting atmospheric escape from PCb and other similar M-dwarf planets. We assumed dissociative recombination of O2+ is the main source reaction for the escape of neutral O atoms and generation of the hot O corona as on Mars and Venus. Our simulation results show that variability of the stellar dynamic pressure does not affect the overall spatial structure of the hot O corona, but the global O escape rate increases by an order of magnitude during high stellar pressure. The escape increases dramatically when the planet possesses its intrinsic magnetic fields as the local cusp regions serve as a reservoir for hot O production. The highly extended hot O corona may lead to a more extended H exosphere through collisions between thermal H and hot O, which exemplifies the importance of considering non-thermal populations in the exosphere for interpretation of future observations. 


The MACH Center

Dave Brain, University of Colorado

Description of MACH Center


Extrasolar Space Weather Monitoring: Stellar and Planetary Radio Emission as a Probe of Habitability

Marin Anderson, Jet Propulsion Laboratory, California Institute of Technology

Both stellar magnetic activity — transient mass loss events like coronal mass ejections (CMEs) and stellar energetic particles (SEPs) — and exoplanet magnetospheres play an important role in defining habitability. Radio observations provide a unique window to both phenomena, and have been well-studied in our own solar system, from solar radio bursts associated with space weather events like CMEs and SEPs, to auroral radio emission from all the magnetized bodies in the solar system.The relevance of planetary magnetic fields to atmospheric retention and, consequently, habitability, remains an important open question. Detection of exoplanet magnetic fields and atmospheres would provide a large and diverse sample of objects outside our solar system with which to examine this question. Similarly, radio observations of a large and diverse sample of nearby stars are critical for understanding stellar space weather environments – especially the prevalence of CMEs on other stars, about which very little is currently known. I will present ongoing work with the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA), a low-frequency radio array that is pioneering the concept of extrasolar space weather monitoring and targeting exoplanet magnetospheres. I will conclude by looking towards the future of radio observations of stars and exoplanets with next-generation, space-based radio arrays.

Posters


Time (MDT) First Author Topic
9:30AM-11:30AM Agnit Mukhopadhyay

Learnings from the Paleo-Magnetosphere: Global Simulations of a Geomagnetic Excursion using Historic Rock Magnetism Records

9:30AM-11:30AM Akifumi Nakayama

Thermal escape in Earth-like terrestrial exoplanets and early Earth with intense XUV environments

9:30AM-11:30AM Anna Mittelholz

Timing of the martian dynamo

9:30AM-11:30AM Antonio Renzaglia

Martian Crustal Field Modifications in the Dayside Ionosphere

9:30AM-11:30AM Arnab Basak

Solar wind forcing of planetary environments in the presence and absence of intrinsic magnetospheres

9:30AM-11:30AM Catherine Regan

Investigating the 2007 global scale dust storm at Mars with ASPERA-3

9:30AM-11:30AM Dave Brain

The MACH Center

9:30AM-11:30AM Dimitra Atri

Modeling the impact of stellar XUV radiation and energetic charged particles on atmospheric escape and planetary habitability

9:30AM-11:30AM Girish M. Duvvuri

Reconstructing the Extreme Ultraviolet Emission of Cool Dwarfs

9:30AM-11:30AM Gopal Hazra

Effect of Stellar Coronal Mass Ejection (CME) and Flare on the atmosphere of hot Jupiter HD189733b and its transit signature

9:30AM-11:30AM Greg Cooke

Atmospheric escape on oxygenated Earth-like exoplanets and possible observational states

9:30AM-11:30AM Hassan Akbari

Ion streaming instability and solitary structures associated with escaping planetary ions at Mars

9:30AM-11:30AM Hiromu Nakagawa

Martian Crustal Field Modifications in the Dayside Ionosphere

9:30AM-11:30AM James A. G. Jackman

The Disconnect between UV and White-Light Flares in Low-Mass Stars

9:30AM-11:30AM Jamie Jasinski

Seasonal dependency of exospheric loss due to photoionization at Mercury

9:30AM-11:30AM Jason Ling

Detection of Young Stars and a Brown Dwarf at Low Radio Frequencies

9:30AM-11:30AM Julián D. Alvarado-Gómez

HoME: Habitability of Magnetized Environments

9:30AM-11:30AM Kai Zhao

Dependences of H+ and O+ Outflows from the Dayside Cusp Region and the Nightside Aurora: a comparison study

9:30AM-11:30AM Kanako Seki

Effects of crustal magnetic fields on the atmospheric ion escape from Mars observed by MAVEN

9:30AM-11:30AM Katerina Stergiopoulou

A two-spacecraft study of Mars’ induced magnetosphere’s response to upstream conditions

9:30AM-11:30AM Laura Harbach

MHD Effects of the Stellar Wind on Observations of Escaping Exoplanet Atmospheres

9:30AM-11:30AM Marianna Felici

Cassini observations of ionospheric plasma in Saturn’s magnetosphere

9:30AM-11:30AM Mats André

Using an enhanced spacecraft wake to detect escaping ionospheric ions

9:30AM-11:30AM Mats Holmstrom

Estimating Ion Escape from Unmagnetized Planets

9:30AM-11:30AM Matthew Fillingim

Terrestrial Ionospheric Ions Observed at Lunar Orbit

9:30AM-11:30AM Nao Yoshida

Seasonal and dust related variations of the dayside thermospheric and ionospheric compositions of Mars observed by MAVEN/NGIMS

9:30AM-11:30AM Naritoshi Kitamura

Solar zenith angle dependence of relationships between energy inputs to the ionosphere and ion outflow fluxes

9:30AM-11:30AM Niharika Godbole

Observations of Ion Upflow in Conjunction with Pulsating Aurora

9:30AM-11:30AM Oliver Hamil

Small-scale magnetic structure in the Martian ionosphere

9:30AM-11:30AM Robert Kavanagh

Planet-induced radio emission from the coronae of M dwarfs

9:30AM-11:30AM Sae AIZAWA

Escape of planetary ions from Mercury’s magnetosphere under different solar wind conditions

9:30AM-11:30AM Dr. Shivangi Bhardwaj

Geomagnetic storms effect on foF2 of ionosphere at mid lattitude

9:30AM-11:30AM Shotaro Sakai

Effects of the IMF direction on atmospheric escape from a Mars-like planet under weak intrinsic magnetic field conditions

9:30AM-11:30AM Stephen Carolan

Star-planet interactions in Close-in Exoplanets: high energy irradiation versus strong stellar winds

9:30AM-11:30AM Tomoaki Nishioka

Study of atmospheric ion escape from exoplanet TOI-700 d based on multi-species MHD simulation.

9:30AM-11:30AM James A. G. Jackman

The Disconnect between UV and White-Light Flares in Low-Mass Stars

9:30AM-11:30AM Tsareva Olga

Atmospheric escape from the Earth during geomagnetic reversal

9:30AM-11:30AM Valery I. Shematovich

Atomic oxygen loss during proton auroral events at Mars

9:30AM-11:30AM Wenyi Sun

Literature Review: Simulated Ion Escape of Mars, Venus, and Earth

9:30AM-11:30AM Yuni Lee

Exosphere of Proxima Centauri B – Photochemical escape from exoplanets