PS – Planetary & Solar System Sciences

PS2.2 – Space environments of unmagnetized or weakly magnetized solar system bodies and the effects of space weather on these systems

EGU22-62 | Presentations | PS2.2

Full-kinetic global simulations of the plasma environment at Mercury: a model from planetary to electrons scales to support BepiColombo

Federico Lavorenti, Pierre Henri, Francesco Califano, Jan Deca, Sae Aizawa, and Nicolas Andre

Mercury is the only telluric planet of the solar system, other than Earth, with an intrinsic magnetic field. Thus, the Hermean surface is shielded from the impinging solar wind via the presence of an “Earth-like” magnetosphere. However, this cavity is twenty times smaller than its alike at the Earth. The relatively small extension of the Hermean magnetosphere enables us to model it using global full-kinetic simulation with the aid of modern supercomputers. Such modeling is crucial to interpret, and prepare, the future observations of the ongoing joint ESA-JAXA mission BepiColombo.

The model used in this work is based on three-dimensional, implicit full-PIC simulations of the interaction between the solar wind and Mercury’s magnetosphere (i.e. at 0.3-0.47 AU). This model includes self-consistently the ion and electron physics down to kinetic electron scales. On top of that, we show comparisons between in-situ observations by Mariner-X and BepiColombo space missions. This comparison allows us (i) to validate our model and (ii) to gain insights into the electron dynamics in the Hermean environment, thought to be governed by kinetic-scale processes.

First, we validate our model through a qualitative comparison between three-dimensional outcomes of our global simulations and the ones of reduced fluid/hybrid simulations (in the context of the SHOTS collaboration). Moreover, comparison with in-situ Mariner-X observations during its first Mercury flyby complete the validation of our model. Second, we study the global dynamics of electrons showing regions where strongest particle acceleration/energization occurs, giving quantitative estimate of electron temperature anisotropy in the Hermean environment. Such results are used to interpret past, and plan future, BepiColombo in-situ observations.

How to cite: Lavorenti, F., Henri, P., Califano, F., Deca, J., Aizawa, S., and Andre, N.: Full-kinetic global simulations of the plasma environment at Mercury: a model from planetary to electrons scales to support BepiColombo, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-62, https://doi.org/10.5194/egusphere-egu22-62, 2022.

EGU22-8557 | Presentations | PS2.2

A magnetosheath hydrodynamic plasma flow model around Mercury

Daniel Schmid, Yasuhito Narita, Ferdinand Plaschke, Martin Volwerk, Rumi Nakamura, and Wolfgang Baumjohann

The magnetosheath is defined as the plasma region between the bow shock, where the super-magnetosonic solar wind plasma is decelerated and heated, and the outer boundary of the intrinsic planetary magnetic field, the so-called magnetopause. Recently we  presented an analytical magnetosheath plasma flow model around Mercury, which can be used to estimate the plasma flow magnitude and direction at any given point in the magnetosheath exclusively on the basis of the plasma parameters of the upstream solar wind. However, this model assumes a constant plasma density and velocity along the flowlines. Here we present a more sophisticated model were we take hydrodynamic effects into account, to also obtain the density and velocity change along the flowline. The model serves as a useful tool to trace the magnetosheath plasma along the streamline both in a forward sense (away from the shock) and a backward sense (toward the shock), offering the opportunity of studying the growth or damping rate of a particular wave mode or evolution of turbulence energy spectra along the streamline in view of upcoming arrival of BepiColombo at Mercury.

How to cite: Schmid, D., Narita, Y., Plaschke, F., Volwerk, M., Nakamura, R., and Baumjohann, W.: A magnetosheath hydrodynamic plasma flow model around Mercury, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8557, https://doi.org/10.5194/egusphere-egu22-8557, 2022.

EGU22-5255 | Presentations | PS2.2

Global hybrid modeling of ultra-low frequency solar wind foreshock waves at Mercury, Venus and Mars

Riku Jarvinen, Esa Kallio, and Tuija Pulkkinen

We study the solar wind interactions of Mercury, Venus and Mars in a global hybrid model, where ions are treated as particles and electrons form a charge-neutralizing fluid. We concentrate on the formation of large-scale, ultra-low frequency (ULF) waves in planetary ion foreshocks and their dependence on solar wind and interplanetary magnetic field conditions in the inner solar system. The ion foreshock forms in the upstream region ahead of the quasi-parallel bow shock, where the angle between the shock normal and the magnetic field is small enough. The magnetic connection to the bow shock allows the backstreaming of solar wind ions leading to the formation of the ion foreshock. This kind of beam-plasma configuration is a source of free energy for the excitation of plasma waves. The foreshock ULF waves convect downstream with the solar wind flow and encounter bow shock and transmit in the downstream region. The analyzed simulation runs use more than two hundred simulation particles per cell on average to allow fine enough velocity space resolution for resolving the foreshocks and waves self-consistently. We find significant differences in wave and foreshock properties between these three planets and discuss their causes.

How to cite: Jarvinen, R., Kallio, E., and Pulkkinen, T.: Global hybrid modeling of ultra-low frequency solar wind foreshock waves at Mercury, Venus and Mars, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5255, https://doi.org/10.5194/egusphere-egu22-5255, 2022.

EGU22-4175 | Presentations | PS2.2

LatHyS hybrid simulation of the August, 10 2021 BepiColombo Venus flyby

Sae Aizawa, Moa Persson, Thibault Menez, Nicolas Andre, Ronan Modolo, Alain Barthe, Emmanuel Penou, Andrei Fedorov, Jean-Andre Sauvaud, Francois Leblanc, Jean-Yves Chaufray, Yoshifumi Saito, Shoichiro Yokota, Go Murakami, Vincent Genot, Beatriz Sanchez-Cano, Daniel Heyner, Tim Horbury, Philippe Louarn, and Christopher Owen

The 2nd Venus flyby of BepiColombo has been examined and compared by the newly developed global hybrid simulation LatHyS for the Venusian environment. The LatHyS has been first validated by comparison with Venus Express observations, then using the observation from Solar Orbiter, which was located in the upstream region and both observed the same solar wind, it is applied for the Venus flyby. The simulation successfully reproduced the observed signatures and it shows that BepiColombo passed through the stagnation region of Venus, which supports the results obtained by data-analysis. In addition, we have sampled the plasma information along the trajectory and constructed the energy spectrum for three species (solar wind proton, planetary proton, and planetary oxygen ion) and possible effect due to the limited field of view is discussed. Moreover, ion escape from Venus for planetary species have been discussed and the escape rate is estimated. 

How to cite: Aizawa, S., Persson, M., Menez, T., Andre, N., Modolo, R., Barthe, A., Penou, E., Fedorov, A., Sauvaud, J.-A., Leblanc, F., Chaufray, J.-Y., Saito, Y., Yokota, S., Murakami, G., Genot, V., Sanchez-Cano, B., Heyner, D., Horbury, T., Louarn, P., and Owen, C.: LatHyS hybrid simulation of the August, 10 2021 BepiColombo Venus flyby, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4175, https://doi.org/10.5194/egusphere-egu22-4175, 2022.

In 2020 and 2021 both BepiColombo and Solar Orbiter used Venus for a gravity assist in order to reach Mercury and to finally get into the correct orbit around the Sun, respectively. These flybys were the first since Mariner 10 to sample a long stretch, more than 30 Venus radii of the induced magnetotail of Venus. This brought the opportunity to study the structure and dynamics of the tail during different solar wind conditions. On this poster we will discuss the differences and also the similarities (even though the four flybys took different trajectories through the induced magnetotail) using the magnetometers on both spacecraft. Field line draping, magnetic reconnection, and plasma waves will all pass by on stage.

How to cite: Volwerk, M. and the The VenusMagTeam: Two Spacecraft, Four Flythroughs: Magnetometer Measurements by BepiColombo and Solar Orbiter in the Induced Magnetotail of Venus, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-822, https://doi.org/10.5194/egusphere-egu22-822, 2022.

EGU22-1821 | Presentations | PS2.2

First evidence of carbon escape through Venus magnetosheath along draped magnetic field lines

Lina Hadid and the MSA, MIA and MEA teams

On August 10, 2021, the Mercury-bound BepiColombo spacecraft flew for the second time by Venus for a Gravity-Assist Maneuver. During this second flyby of Venus, a limited number of instruments were turned on, allowing unique observations of the planet and its environment. Among these instruments, the Mass Spectrum Analyzer (MSA) that is part of the particle analyzer consortium onboard the magnetospheric orbiter (Mio) was able to acquire its first plasma composition measurements in space. As a matter of fact, during a limited time interval upon approach of the planet, substantial ion populations were recorded by MSA, with characteristic energies ranging from about 20 eV up to a few hundreds of eVs. Comparison of the measured Time-Of-Flight spectra with calibration data reveals that these populations are of planetary origin, containing both Oxygen and Carbon ions. The Oxygen observations are to some extent consistent with previous in situ measurements from mass spectrometers onboard Venus Express and Pioneer Venus Orbiter. On the other hand, the MSA data provide the first ever in situ evidences of Carbon ions in the near-Venus environment at about 6 planetary radii. We show that the abundance of C+ amounts to about ~30% of that of O+. Furthermore, the fact that photoelectrons are simultaneously observed with the low energy planetary ions indicate a magnetic connection to the dayside ionosphere from which ions are ejected under the effect of the ambipolar electrostatic field.

How to cite: Hadid, L. and the MSA, MIA and MEA teams: First evidence of carbon escape through Venus magnetosheath along draped magnetic field lines, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1821, https://doi.org/10.5194/egusphere-egu22-1821, 2022.

EGU22-3658 | Presentations | PS2.2

Solar Orbiter Data-Model Comparison in Venus' Induced Magnetotail

Katerina Stergiopoulou, Riku Jarvinen, David J. Andrews, Niklas J.T. Edberg, Andrew P. Dimmock, Esa Kallio, and Yuri Khotyaintsev

We investigate the Venusian magnetotail and its boundaries utilising magnetic field and density measurements that cover a wide range of radial distances, from the two geometrically similar Solar Orbiter Venus flybys on 27 December 2020 and 9 August 2021. We look at the magnetic field components along the spacecraft trajectory in an attempt to identify boundary crossings, as well as the extent and intensity of the bowshock deep in the magnetotail. We compare these observations with results of a simulation of the induced magnetosphere and magnetotail of Venus, where the initial upstream conditions are provided by Solar Orbiter measurements, to examine in what degree the simulation representation agrees with the observations. The model encloses a massive volume of 80RV x 60RV x 60RV  in which we look at magnetic field and proton density variations. Additionally, we vary the rotation of the clock angle in order to find for which rotation angle we get the best match with the observations during the different steps of the spacecraft's trajectory. 

How to cite: Stergiopoulou, K., Jarvinen, R., Andrews, D. J., Edberg, N. J. T., Dimmock, A. P., Kallio, E., and Khotyaintsev, Y.: Solar Orbiter Data-Model Comparison in Venus' Induced Magnetotail, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3658, https://doi.org/10.5194/egusphere-egu22-3658, 2022.

EGU22-6696 | Presentations | PS2.2

Spatially Highly Resolved Solar-wind-induced Magnetic Field on Venus

Maosheng He, Joachim Vogt, Eduard Dubinin, Tielong Zhang, and Zhaojin Rong

The current work investigates the Venusian solar-wind-induced magnetosphere at a high spatial resolution using all Venus Express (VEX) magnetic observations through an unbiased statistical method. We first evaluate the predictability of the interplanetary magnetic field (IMF) during VEX's Venusian magnetospheric transits and then map the induced field in a cylindrical coordinate system under different IMF conditions. Our mapping resolves structures on various scales, ranging from the ionopause to the classical IMF draping. We also resolve two recently reported structures, a low-ionosphere magnetization over the terminator, and a global "looping" structure in the near magnetotail. In contrast to the reported IMF-independent cylindrical magnetic field of both structures, our results illustrate their IMF dependence. In both structures, the cylindrical magnetic component is more intense in the hemisphere with an upward solar wind electric field (E^SW) than in the opposite hemisphere. Under downward E^SW, the looping structure even breaks, which is attributable to an additional draped magnetic field structure wrapping toward −E^SW. In addition, our results suggest that these two structures are spatially separate. The low-ionosphere magnetization occurs in a very narrow region, at about 88°–95° solar zenith angle and 185–210 km altitude. A least-squares fit reveals that this structure is attributable to an antisunward line current with 191.1 A intensity at 179 ± 10 km altitude, developed potentially in a Cowling channel.

How to cite: He, M., Vogt, J., Dubinin, E., Zhang, T., and Rong, Z.: Spatially Highly Resolved Solar-wind-induced Magnetic Field on Venus, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6696, https://doi.org/10.5194/egusphere-egu22-6696, 2022.

EGU22-4000 | Presentations | PS2.2

Influence of planetary space weather on the shapes of Venus plasma boundaries

Claire Signoles, Moa Persson, Alexander Wolff, Nicolas Martinez, Viktor Lindwall, Yoshifumi Futaana, Sebastian Rojas-Mata, Tielong Zhang, Nicolas André, Sae Aizawa, and Andrei Fedorov

As Venus does not have an intrinsic magnetic field, the solar wind interacts directly with the Venusian atmosphere, altering its structure and composition, for example through atmospheric ion escape to space. In particular, the interaction will result in the formation of plasma boundaries, which separate regions of different plasma populations around Venus. Knowing how space weather influences the shape of these boundaries is one of the key pieces to understanding the current state of the Venusian atmosphere.

During its eight years mission, including more than 3000 orbits around Venus, Venus Express made measurements of the plasma environment, covering a wide range of upstream conditions. Using conjoint plasma and magnetic field measurements from the ASPERA-4 (Analyser of Space Plasma and Energetic Atoms) and the magnetometer instruments, we identified the locations where the spacecraft crossed the bow shock and the ion composition boundary for each orbit. Using the derived dataset, we then determined the boundary shapes with a two-parameter fit. The boundary shape fittings were done with respect to one or multiple upstream conditions.

Here we report that both boundaries are highly dependent on solar wind extreme ultraviolet (EUV) flux, expanding further from the planet at solar maximum. A likely explanation is that at solar maximum, combined heating of the exosphere ions and a higher photoionization rate lead to a higher planetary ion production. These additional ions increase the internal thermal pressure, pushing the boundaries outward.

Additionally, at solar minimum, solar wind parameters like dynamic pressure and energy flux were found to not affect the shape of the bow shock, which is consistent with previous studies. The influence of the strength and orientation of the interplanetary magnetic field, the Mach number, and potential correlations between multiple upstream parameters, are also discussed in this talk.

How to cite: Signoles, C., Persson, M., Wolff, A., Martinez, N., Lindwall, V., Futaana, Y., Rojas-Mata, S., Zhang, T., André, N., Aizawa, S., and Fedorov, A.: Influence of planetary space weather on the shapes of Venus plasma boundaries, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4000, https://doi.org/10.5194/egusphere-egu22-4000, 2022.

EGU22-653 | Presentations | PS2.2

Proton Temperature Anisotropies in the Venus Plasma Environment during Solar Minimum and Maximum

Sebastián Rojas Mata, Gabriella Stenberg Wieser, Yoshifumi Futaana, Alexander Bader, Moa Persson, Andrey Fedorov, and Tielong Zhang

Venus’ lack of an intrinsic magnetic field allows the solar wind to closely interact with its atmosphere [1], making it a
prime target for investigating how unmagnetized atmospheric bodies in our Solar System [2] or elsewhere [3] interact
with magnetized plasma flows. This close interaction means that solar-activity correlations exhibited by the solar wind and
other heliospheric parameters [4, 5] cause solar-cycle variations in Venus’ plasma environment and plasma phenomena. We
investigate these variations by characterizing the proton population around Venus during periods of solar minimum (2006–2009)
and maximum (2010–2014). We use data from the Ion Mass Analyser (IMA) instrument, a particle mass-energy spectrometer
which was onboard the Venus Express (VEX) mission. We apply a previously developed methodology which fits Maxwellian
models to measurements of the protons’ velocity distribution functions [6] to produce statistical distributions of bulk speeds and
temperatures in various regions of Venus’ plasma environment. We also present spatial maps and probability-density histograms
comparing the proton parameters between the two time periods.
We find that the temperatures perpendicular (T) and parallel (T) to the background magnetic field are 20–35% lower
in the magnetosheath during solar maximum. This suggests that the heating of particles as they cross the bow shock varies
between the two time periods. We also find that the regions in the magnetosheath with highest temperature ratio T/T are
farther downstream from the bow shock during solar maximum than minimum. This is consistent with previous observations of
how mirror-mode structures presumably generated at the bow shock strictly decay as they are convected into the magnetosheath
during solar minimum, whereas during solar maximum they first grow and then decay [7]. We also present ongoing work to
further characterize the plasma environment as a function of upstream solar-wind parameters (such as Mach number or cone
angle) and bow shock geometry. We discuss preliminary results concerning energy conversion processes at Venus’ bow shock.


REFERENCES
[1] Y. Futaana, G. Stenberg Wieser et al., “Solar Wind Interaction and Impact on the Venus Atmosphere,” Space Science Reviews, vol. 212, no. 3-4, 2017.
[2] C. Bertucci, F. Duru et al., The induced magnetospheres of mars, venus, and titan, 2011, vol. 162, no. 1-4.
[3] C. Dong, M. Jin et al., “Atmospheric escape from the TRAPPIST-1 planets and implications for habitability,” Proceedings of the National Academy of
Sciences of the United States of America, vol. 115, no. 2, 2017.
[4] C. T. Russell, E. Chou et al., “Solar and interplanetary control of the location of the Venus bow shock,” Journal of Geophysical Research, vol. 93, no. A6, 1988.
[5] P. R. Gazis, “Solar cycle variation in the heliosphere,” Reviews of Geophysics, vol. 34, no. 3,  1996.
[6] A. Bader, G. Stenberg Wieser et al., “Proton Temperature Anisotropies in the Plasma Environment of Venus,” Journal of Geophysical Research: Space
Physics, vol. 124, no. 5, 2019.
[7] M. Volwerk, D. Schmid et al., “Mirror mode waves in Venus’s magnetosheath: Solar minimum vs. solar maximum,” Annales Geophysicae, vol. 34, no. 11, 2016.

How to cite: Rojas Mata, S., Stenberg Wieser, G., Futaana, Y., Bader, A., Persson, M., Fedorov, A., and Zhang, T.: Proton Temperature Anisotropies in the Venus Plasma Environment during Solar Minimum and Maximum, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-653, https://doi.org/10.5194/egusphere-egu22-653, 2022.

EGU22-5413 | Presentations | PS2.2

Mirror mode-like structures around unmagnetised planets: a comparison between the magnetosheaths of Mars and Venus

Cyril Simon Wedlund, Martin Volwerk, Christian Mazelle, Sebastián Rojas Mata, Gabriella Stenberg Wieser, David Mautner, Jasper Halekas, Jared Espley, Diana Rojas-Castillo, Christian Möstl, and César Bertucci

Mirror mode structures arise whenever a temperature anisotropy is present in the plasma, classically in the wake of the bow shock in a quasi-perpendicular configuration with respect to the interplanetary magnetic field, or from pickup ion distribution effects. Born from space plasma instabilities and in competition with other wave modes, these ultra-low frequency waves contribute to energy exchanges between the different plasma populations present in the magnetosheath. At Mars and Venus, such structures have very similar scales: they last typically a few tens of seconds and appear as peaks or dips in the magnetic field data in antiphase with the local plasma density variations. As magnetometers are present on many space missions, magnetic field-only criteria are an ideal tool to study these structures across different magnetosheath environments. We present here for the first time a comparison of the statistical occurrence of magnetosheath mirror mode-like structures at Mars with MAVEN and at Venus with Venus Express. Based on magnetic field-only measurements, we use identical detection criteria at both planets to select quasi-linear structures in B-field measurements. We then present two-dimensional maps of mirror mode-like occurrence rates with respect to solar cycle variations and EUV flux levels, atmospheric seasons (for Mars) and the nature of the shock crossing (quasi-parallel or quasi-perpendicular configurations), and compare them between planets. Finally, we discuss ambiguities in the nature of the detected structures and their global effects on the magnetosheath.

How to cite: Simon Wedlund, C., Volwerk, M., Mazelle, C., Rojas Mata, S., Stenberg Wieser, G., Mautner, D., Halekas, J., Espley, J., Rojas-Castillo, D., Möstl, C., and Bertucci, C.: Mirror mode-like structures around unmagnetised planets: a comparison between the magnetosheaths of Mars and Venus, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5413, https://doi.org/10.5194/egusphere-egu22-5413, 2022.

EGU22-1609 | Presentations | PS2.2

Ranking the drivers of the Martian bow shock location: a statistical analysis of Mars Atmosphere and Volatile EvolutioN and Mars Express observations

Philippe Garnier, Christian Jacquey, Xavier Gendre, Vincent Génot, Christian Mazelle, Xiaohua Fang, Jacob Gruesbeck, Beatriz Sanchez-Cano, and Jasper Halekas

The Martian interaction with the solar wind leads to the formation of a bow shock upstream of the planet. The shock dynamics appears complex, due to the combined influence of external (solar photons, solar wind plasma and fields) and internal (crustal magnetic fields, ionized atmosphere) drivers. The extreme ultraviolet fluxes and magnetosonic mach number are known major drivers of the shock location, while the influence of other possible drivers is less constrained or unknown such as crustal magnetic fields or the solar wind dynamic pressure and the Interplanetary Magnetic Field (IMF) intensity and orientation.

We analyze and rank the influence of the main drivers of the Martian shock location, based on published datasets from Mars Express and Mars Atmosphere Volatile EvolutioN missions and on several methods such as the Akaike Information Criterion, Least Absolute Shrinkage Selection Operator regression, and partial correlations. We include here the influence of the crustal fields, extreme ultraviolet fluxes, magnetosonic mach number, solar wind dynamic pressure and various Interplanetary Magnetic Field parameters (intensity and orientation angles).

We conclude that the major drivers of the shock location are extreme ultraviolet fluxes and magnetosonic mach number, while crustal fields and solar wind dynamic pressure are secondary drivers at a similar level. The IMF orientation also plays a significant role, with larger distances for perpendicular shocks rather than parallel shocks.

How to cite: Garnier, P., Jacquey, C., Gendre, X., Génot, V., Mazelle, C., Fang, X., Gruesbeck, J., Sanchez-Cano, B., and Halekas, J.: Ranking the drivers of the Martian bow shock location: a statistical analysis of Mars Atmosphere and Volatile EvolutioN and Mars Express observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1609, https://doi.org/10.5194/egusphere-egu22-1609, 2022.

EGU22-169 | Presentations | PS2.2

On the Growth and Development of Non-linear Kelvin-Helmholtz Instability at Mars: MAVEN Observations

Gangkai Poh, Jared Espley, Katariina Nykyri, Christopher Fowler, Xuanye Ma, Shaosui Xu, Gwen Hanley, Norberto Romanelli, Charles Bowers, Jacob Gruesbeck, and Gina DiBraccio

We analyzed MAVEN observations of fields and plasma signatures associated with an encounter of fully-developed Kelvin–Helmholtz (K–H) vortices at the northern polar terminator along Mars’ induced magnetosphere boundary. The signatures of the K–H vortices event are: (i) quasi-periodic, “bipolar-like” sawtooth magnetic field perturbations, (ii) corresponding density decrease, (iii) tailward enhancement of plasma velocity for both protons and heavy ions, (iv) co-existence of magnetosheath and planetary plasma in the region prior to the sawtooth magnetic field signature (i.e. mixing region of the vortex structure), and (v) pressure enhancement (minimum) at the edge (center) of the sawtooth magnetic field signature. Our results strongly support the scenario for the non-linear growth of K–H instability along Mars’ induced magnetosphere boundary, where a plasma flow difference between the magnetosheath and induced-magnetospheric plasma is expected. Our findings are also in good agreement with 3-dimensional local magnetohydrodynamics (MHD) simulation results. MAVEN observations of protons with energies greater than 10 keV and results from the Walén analyses suggests the possibility of particle energization within the mixing region of the K–H vortex structure via magnetic reconnection, secondary instabilities or other turbulent processes. We estimated the lower limit on the K–H instability linear growth rate to be ~5.84 x 10-3 s-1. For these vortices, we estimate the lower limit of the instantaneous atmospheric ion escape flux due to the detachment of plasma clouds during the late non-linear stage of K–H instability to be ~5.90 x 1026 particles/s, which is agrees with earlier studies for the Venusian plasma clouds but ~two orders of magnitude larger than that calculated for Mars. 

How to cite: Poh, G., Espley, J., Nykyri, K., Fowler, C., Ma, X., Xu, S., Hanley, G., Romanelli, N., Bowers, C., Gruesbeck, J., and DiBraccio, G.: On the Growth and Development of Non-linear Kelvin-Helmholtz Instability at Mars: MAVEN Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-169, https://doi.org/10.5194/egusphere-egu22-169, 2022.

EGU22-2853 | Presentations | PS2.2

Exploring the solar wind-planetary interaction at Mars: Implication for Magnetic Reconnection

Charles F. Bowers, Gina A. DiBraccio, James A. Slavin, Jacob R. Gruesbeck, Tristan Weber, Norberto Romanelli, Abigail R. Azari, and Shaosui Xu

The Martian crustal magnetic anomalies create a varied, asymmetric obstacle for the draped interplanetary magnetic field (IMF) to interact with. One possible result of this interaction is magnetic reconnection, a process by which anti-parallel magnetic field lines connect and reconfigure, transferring energy into the surrounding environment and mixing previously separated plasma populations. Here, we present an analysis to determine the draped IMF conditions that favor reconnection with the underlying crustal anomalies at Mars. First, we plot a map of the crustal anomalies’ strength and orientation compiled from magnetic field data taken throughout the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. Second, we create “shear maps” which calculate and plot the angle of shear between the transverse component of the anomalies and a chosen overlaid draping direction. Third, we define a “shear index” which quantifies the susceptibility of a particular region to undergo reconnection based on a given draped IMF orientation and the resulting shear map for that region. We then compare the shear index for a variety of draped field orientations within different regions of the Martian magnetosphere. Our results suggest eastward/westward (horizontal) draped fields present regions that are more likely for anti-parallel magnetic reconnection to occur with the crustal anomalies than northward/southward (vertical) draped fields, with one notable exception being the strongest crustal anomalies located in the southern hemisphere ~180° longitude. An east/west draped field roughly corresponds to a +/- By IMF direction on the dayside, implying the rate of magnetic reconnection on the dayside of Mars may be enhanced for IMF field lines pointing in the +/- YMSO direction compared to that of IMF field lines pointing in the +/- ZMSO direction, with MSO referring to the Mars Solar Orbital coordinate system. Understanding the interplay between Mars’s crustal magnetic fields and the IMF is crucial to answer outstanding science questions regarding nightside magnetospheric activity at Mars, namely how IMF orientation affects the twisting of the magnetotail, open magnetic topology observations on the nightside, and discrete aurora observations in the southern hemisphere.

How to cite: Bowers, C. F., DiBraccio, G. A., Slavin, J. A., Gruesbeck, J. R., Weber, T., Romanelli, N., Azari, A. R., and Xu, S.: Exploring the solar wind-planetary interaction at Mars: Implication for Magnetic Reconnection, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2853, https://doi.org/10.5194/egusphere-egu22-2853, 2022.

EGU22-4455 | Presentations | PS2.2

Estimating heavy ions escape rate from Mars using hybrid model and observations from MAVEN

Qi Zhang, Mats Holmström, Xiaodong Wang, and Shahab Fatemi

We apply a new method, coupling a hybrid plasma model (ions as particles, electrons as a fluid) and measurements from the Mars Atmosphere and Volatile Evolution (MAVEN) mission, to calculate heavy ion escape rates from Mars. With this method, we acquire estimates of the escape rate orbit by orbit in different upstream conditions. We have investigated how the estimated ion escape depends on the assumed composition of heavy ions, the solar wind velocity aberration and the amount of alpha particles in the solar wind. We also estimate the amount of tail escape and radial escape and compare the model results with  recent Mars Express and MAVEN studies.

How to cite: Zhang, Q., Holmström, M., Wang, X., and Fatemi, S.: Estimating heavy ions escape rate from Mars using hybrid model and observations from MAVEN, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4455, https://doi.org/10.5194/egusphere-egu22-4455, 2022.

EGU22-1814 | Presentations | PS2.2

A Fully Kinetic Perspective on Weakly Active Comets: Symmetric versus Asymmetric Outgassing

Jan Deca, Peter Stephenson, Andrey Divin, Pierre Henri, and Marina Galand

For more than two years, ESA’s Rosetta mission measured the complex and ever-evolving plasma environment surrounding comet 67P/Churyumov-Gerasimenko. In this work, we explore the structure and dynamics of the near-comet plasma environment at steady state, comparing directly the results of a spherically symmetric Haser model and an asymmetric outgassing profile based on the measurements from the ROSINA instrument onboard Rosetta during 67P’s weakly outgassing stages. Using a fully kinetic semi-implicit particle-in-cell code, we are able to characterise (1) the various ion and electron populations and their interactions, and (2) the implications to the mass-loading process caused by taking into account asymmetric outgassing. Our model complements observations by providing a full 3D picture that is directly relevant to help interpret the measurements made by the Rosetta Plasma Consortium instruments. In addition, understanding such details better is key to help disentangle the physical drivers active in the plasma environment of comets visited by future exploration missions.

How to cite: Deca, J., Stephenson, P., Divin, A., Henri, P., and Galand, M.: A Fully Kinetic Perspective on Weakly Active Comets: Symmetric versus Asymmetric Outgassing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1814, https://doi.org/10.5194/egusphere-egu22-1814, 2022.

EGU22-9415 | Presentations | PS2.2

Discrete Aurora on Mars: Insights into reconnection? 

Nicholas Schneider, Ben Johnston, Sonal Jain, Zac Milby, Charlie Bowers, Gina Dibraccio, Jean-Claude Gérard, and Lauriane Soret

Analysis of nightside nadir-viewing observations taken by MAVEN's Imaging Ultraviolet Spectrograph instrument has identified nearly 200 discrete aurora emissions.  Discrete aurora are sporadic localized ultraviolet emissions originating in the upper Martian atmosphere that occur brightest and most frequently near regions of strong crustal magnetic field strength.  The emission detections were verified and characterized by visual appearance across the disk and spectral analysis of Cameron band and ultraviolet doublet emissions.  No geographic or magnetic field information was used to determine whether a suspected emission was real or an artifact in the data.   Unlike limb observations, nadir observations have no line-of-sight ambiguity, allowing us to locate the emissions with high geographic accuracy.  Nadir viewing also provides global coverage of the nightside disk, giving broad geographic and local time coverage.  We find the same dependence on local time, crustal field strength and interplanetary magnetic field orientation seen in limb observations (Schneider et. al. 2021).  

A large fraction of the observed events occur in open field regions associated with the strongest radial magnetic fields. These events occur along approximately east-west lines at the footprints of two magnetic field arcades, one with a north-directed horizontal crustral field and one south-directed (see below). Observations show that these arcades become active in an auroral sense at opposite times of night, one pre-midnight and the other post-midnight. We will show that the geometry of draping of the interplanetary magnetic field over the crustal fields provides a natural explanation for the different local time auroral triggerings, with magnetic reconnection more likely in one arcade pre-midnight and the other post-midnight.
 
    Figure 1: Mars Crustal Magnetic Field Geometry