TP18

Figure 1. Velocity vectors of the H+ ions projected on the YZ-plane compiled from the VEX measurements (From Lundin et al., GRL, 40(7), 273,  2013).

By collecting data from VEX orbits obtained when the spacecraft entered and exited a vortex structure between 2006 and 2013 those crossings are indicated with the segments placed in Figure 2. As a whole there is a general difference between segments located within two circles that are traced with a preference to occur farther away from Venus (located at the left side) in the 2006-2009 orbits (left circle) with respect to those in the 2010-2013 orbits (right circle). At the same time, there is a corresponding difference in the width of the segments with larger values (higher values in the vertical coordinate) for those placed in the right circle. In particular, since minimum solar cycle conditions were present during the 2009-2013 orbits there is an indication that under such conditions the position of the vortex structures occurred closer to Venus along the wake and at the same time their width becomes larger.

Figure 2. Width of vortex structures in 20 VEX orbits measured downstream from Venus. The numbers at the side of each segment represent the two last digits of the year between 2006 and 2009 prior to a solar cycle minimum (left circle) and between 2009 and 2013 during that time period (right circle) (Pérez-de-Tejada and Lundin. IntechOpen, ISBN-978-1-83969-313-7), 2021.

 Such properties are compatible with the shape of a corkscrew flow in fluid dynamics depicted in Figure 3 in which its thickness decreases with distance downstream from an object immersed in a flow.

The decrease of the overall size of vortices with distance along the Venus wake as noted in Figure 2 has important implications regarding its effects on the motion of the planetary ions that stream in the wake. Most notable is that their kinetic energy around those features depends on the scale size of vortices and if the latter become smaller with the downstream distance as produced by the expansion of the solar wind into the wake the energy released should be assimilated by particles that remain moving in the smaller size vortices. In addition, such particles have directed motion along the wake and as a result, some of that energy may contribute to enhance their speed in that direction. It is thus possible that a fraction of planetary O+ ions dragged along by the solar wind may be gradually accelerated along the Venus wake. 

The acceleration of those particles can be estimated in terms of the change that the cross section of the vortex structures experience along the wake and that as shown in Figure 4 produces an increase in their speed in both panels from ~10 km/s by ~5 10³ km altitude to ~40 km/s by ~10⁴ km.  Following the shape of a vortex structure downstream from Venus similar to that indicated in the equivalent form past an object in Figure 3 we can suggest a shape that by two planetary radii downstream from Venus the thickness of the vortex should have decreased. The outcome of that geometry is that when the thickness of the corkscrew flow decreases along the wake the speed of the particles has to be larger so that their kinetic energy density integrated over the area of the cross section is preserved.

Figure 3. View of a corkscrew vortex flow in fluid dynamics. Its geometry is equivalent to that expected for a vortex flow in the Venus wake. The vortex flow becomes thinner when it is detected further downstream from Venus as suggested from the data in Figure 2 (from Pérez de Tejada and, Lundin, Intech Open (ISBN-978-1-83969 -313-7), 2021. 

Figure 4. Speed profiles of the solar wind and ionospheric ions as a function of altitude measured in the dawn-dusk (left) and in the noon-midnight meridian (right) (from Lundin et al., ICARUS, 215, 751, 2011).

 Variations in the speed profiles with altitude measured in the dawn-dusk and in the dawn-dusk meridians across the Venus wake are compatible with those expected from the shape of the corkscrew flow in Figure 3 where larger speed values should be encountered where the cross section of the vortex structure is smaller. Thus, the data points in Figure 4 at low altitudes refer to the motion of the spacecraft through a wide vortex in a region close to Venus and at higher altitudes apply where the cross section of the vortex is smaller and hence the flow speeds are larger as it is the case by ~10⁴ km altitude.

An implication also consistent with the shape of a corkscrew flow shape in Figure 3 is the abrupt ending of the speed profile by ~ 1.5 10⁴ km altitude in both panels of Figure 4 and that is not related to any drastic change in the density profile since comparable density values were measured above and below that altitude. Instead, the abrupt ending of the speed profile at that altitude may imply the exit of the spacecraft from the corkscrew flow region along its trajectory. Measurement of planetary ion flows in the Venus near wake also suggest that they proceed under superalfvenic conditions and thus are unrelated to magnetic field effects (Pérez-de-Tejada et al., JGR, 118, doi: 10.1002/2013JA019029, 2013). At the same time the flow direction appears to be independent of the magnetic field orientation (Lundin, personal communication).                                                                   

How to cite: Pérez-de-Tejada, H. and Lundin, R.: Particle acceleration in the Venus plasma wake, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-64, https://doi.org/10.5194/epsc2022-64, 2022.

The thermal electron temperature, Te, is an important quantity in planetary ionospheres because many photochemical reaction rates depend on it. Te thus plays a role in driving ion composition, structure and dynamics. In addition, enhancements in Te with altitude have been shown to drive ambi-polar electric fields that can energize cold planetary ions and lead to ion escape to space.

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission acquires Te profiles on each orbit and as a result, a comprehensive data set exists that spans the full range of Mars local times, latitudes and solar zenith angles. We will determine which physical processes control the Te profile shapes and temperature values. In particular, we will focus on the “transition region” where Te values can rapidly increase from small values (<500 K) at lower altitudes, to larger values (>1000 K), over a relatively narrow altitude range. The suite of plasma instruments carried by MAVEN allows us to investigate the role of, for example, electron-neutral collisions, ion temperature, wave heating, etc. Understanding the physical processes that control the form of Te profiles will inform us of the mechanisms key to structuring the current day Mars ionosphere. Such understanding will also provide key insight needed for studies of ionospheric escape to space and long term evolution of the Mars atmosphere.

How to cite: Turner, A., Fowler, C., and Andersson, L.: Determining the physical processes that control thermal electron temperature profiles in the Mars ionosphere., Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-146, https://doi.org/10.5194/epsc2022-146, 2022.

Mars is an unmagnetized planet meaning that it has no internally generated global dipole magnetic field; the solar wind interaction with Mars is thus highly dependent on upstream conditions that include the orientation of the Interplanetary Magnetic Field (IMF). This interaction controls the transfer of energy and momentum from the solar wind into the magnetosphere, ionosphere and atmosphere, driving structure and dynamics within each. The Mars-solar wind interaction has been studied in detail for “nominal” Parker Spiral IMF conditions, but few studies exist that investigate the interaction under less typical “radial IMF” conditions. We utilize in-situ measurements made by NASAs Mars Atmosphere and Volatile EvolutioN (MAVEN) mission during radial IMF conditions at Mars to identify several prominent features that arise during this interaction:

• Highly disturbed magnetic and plasma conditions exist over the nose of the planet, which are reminiscent of foreshock like conditions and indicative of radial IMF.
• Solar wind protons and alphas are observed to penetrate directly into the dayside ionosphere down to MAVEN periapsis altitudes (~230 km).
• The magnetic pileup region (or magnetic barrier) forms deep within the dayside ionosphere, directly exposing significant heavy planetary ion densities above to the solar wind flow.
• Planetary ions above the magnetic barrier are mass loaded by the solar wind flow, characterized by signatures consistent with VxB acceleration under near radial IMF conditions.
• Thermal ion distributions in the ionosphere are observed to possess significant suprathermal energetic tails, suggesting that additional energization mechanisms are present that heat the cold ion core. Electron and ion temperatures are 2-10 times higher than average values that occur under more typical IMF conditions.
• Significant erosion of the dayside upper ionosphere occurs and appears to drive substantial ion escape to space.

How to cite: Fowler, C., Hanley, G., McFadden, J., Halekas, J., Schwartz, S., Mazelle, C., Chaffin, M., Mitchell, D., Andersson, L., Espley, J., Ramstad, R., Dong, Y., and Curry, S.: A MAVEN case study of radial IMF at Mars: impacts on the dayside ionosphere, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-233, https://doi.org/10.5194/epsc2022-233, 2022.

Unlike Earth, Venus doesn’t have an intrinsic magnetic field shielding it from the solar wind. However, an induced
magnetic field is generated from the interaction of solar wind and the dense atmosphere of the planet. Recent
Venus flybys by the BepiColombo mission in October 2020 and August 2021, and by Parker Solar Probe and Solar
Orbiter, are unique opportunities to further study the interaction between Venus and the Sun.

Observational data are essential in the study of this interaction but they are limited by the mission’s trajectory,
offering a constrained view of the processes that take place. On the other hand, simulations offer a global view
of the interactions, allowing us to get results with physical significance that would not have been possible from
observational data only. LatHyS is a three-dimensional parallel multi-species model using the hybrid formalism,
that represents the electrons as a massless fluid conserving the neutrality of the plasma, and the ions by numerical
macroparticles with variable weights. Ions and electrons are coupled together using the Maxwell equations, and the
macroscopic plasma parameters determine the evolution of the magnetic field (Ledvina et al. 2008). It was initially
developed at LATMOS, Paris, France, for Mars (Modolo et al. 2005) and later parallelized (Modolo et al. 2016) for
performance and optimization purposes. It has the advantage of having a self consistently calculated ionosphere.
LatHyS was recently adapted to the simulations of the interaction between the solar wind and Venus at IRAP,
Toulouse, France (Aizawa et al. 2022).

The work conducted aims at adapting a multi-grid method, initially adapted to LatHyS by Leclercq et al. 2016
for the study of Mars and Ganymede, to the case of Venus. The multi-grid refinement allows a more efficient use
of computing resources and an improved accuracy of the simulation thanks to a spatial resolution equivalent to or
lower than the ionospheric plasma scale height.

First, the multi-grid method is presented. Then, simulations using the multi-grid method on the solar wind’s
interaction with Venus are conducted, and their results are compared to simulations made using LatHyS with a
single homogeneous grid.
Finally the outputs of the numerical simulations are compared to data on the magnetic field and charged particles
from recent flybys and from the Venus Express mission, that orbited the planet from 2006 to 2014.

References:

Aizawa et al. 2022. https://doi.org/10.1016/j.pss.2022.105499

Leclercq et al. 2016. http://dx.doi.org/10.1016/j.jcp.2016.01.005

Ledvina et al. 2008. http://dx.doi.org/10.1007/s11214-008-9384-6

Modolo et al. 2005. https://doi.org/10.5194/angeo-23-433-2005

Modolo et al. 2016. http://dx.doi.org/10.1002/2015JA022324

How to cite: Jariel, E., Aizawa, S., Modolo, R., Leclercq, L., Baskevitch, C., Andre, N., and Persson, M.: Adapting a multi-grid method to a numerical simulation model of the interaction between Venus and the solar wind, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-417, https://doi.org/10.5194/epsc2022-417, 2022.

While the orbital and environmental parameters (e.g. orbit-Sun-distance, planetary mass/diameter, rotation rate, surface pressure) of Venus and Mars are very different, their planetary ionospheres show many similarities. The photochemically dominated regions of the undisturbed dayside ionospheres of Venus (Figure 1) and Mars (Figure 2) contain two major features: The ionospheric main peak (V2 at Venus and M2 at Mars) both originate from photoionization by solar EUV radiation, while the weaker secondary V1/M1 region is based on the primary and secondary ionization by solar X-ray radiation [1]. The upper region of the Venus and Mars dayside ionospheres is dominated by transport processes. The extent and shape of these regions in Venus Express Radio Science (VEX-VeRa) and Mars Express Radio Science (MEX-MaRS) observations is highly variable on temporal scales and ranges from an undisturbed exponential decay (Figure 1a and 2a) to strongly compressed shapes (Figure 1b and 2b). 

In this work, 9 years of VEX-VeRa (2006-2014) and 18 years of MEX-MaRS (2004-ongoing) radio science observations are used to study the behavior of the upper ionospheric region of Venus and Mars. The identified parameters will be compared to other characteristics of the solar wind interaction region of both planets identified by Venus Express [2], Mars Express [3] and MAVEN [4] to improve our understanding of the solar wind interaction of planets without a global magnetic field. The effect of potential drivers on the temporal variability of the upper ionosphere are investigated for Venus and Mars by comparison with pristine solar wind parameters (e.g. VEX-ASPERA4 [5], MEX-ASPERA3 [6]) and solar radiation fluxes (FISM-V2 model [7], MAVEN EUV monitor [8]).

References

  [1] Fox et al. (1996)  Adv. Space Res., 17 (11).

  [2] Titov et al. (2006)  Cosmic Research 44 (4).

  [3] Fletcher (2004)  Mars Express. The scientific payload. ESA.

  [4] Jakosky B. M. et al. (2015)  SSR, 195, 3-48.

  [5] Barabash et al. (2007)  PSS, 55 (12).

  [6] Barabash et al. (2006)  SSR, 126, 113-164.

  [7] Chamberlin et al. (2020) Space Weather, 18 (12).

  [8] Thiemann et al. (2017)  JGR Space Phys., 122 (3).

How to cite: Peter, K., Pätzold, M., Chu, F., Ramstad, R., Thiemann, E., Fränz, M., Girazian, Z., Kopf, A., Tellmann, S., Häusler, B., Futaana, Y., and Holmström, M.: The variability of the topside ionospheres of Venus and Mars in light of radio science observations, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-857, https://doi.org/10.5194/epsc2022-857, 2022.

The European Space Agency Rosetta mission escorted comet 67P/Churyumov-Gerasimenko for two years, during which it acquired an extensive dataset, revealing unprecedented detail about the neutral and plasma environment of the coma. The measurements were made over a large range of heliocentric distances, and therefore of outgassing activities, as Rosetta witnessed 67P evolve from a low-activity icy body at 3.8 AU to a dynamic object with large-scale plasma structures and rich ion and neutral chemistry near perihelion at 1.2 AU. One such plasma structure is the diamagnetic cavity, a region of negligible magnetic field surrounding the comet nucleus. It is formed through the interaction of the unmagnetized outwardly expanding cometary plasma with the incoming solar wind. This region was encountered many times by Rosetta between April 2015 and February 2016, as the comet moved towards and away from perihelion.

In this study, we focus on the changing role of chemistry during the escort phase, particularly on trends in the detection of high proton affinity species near perihelion and within the diamagnetic cavity. NH₄⁺ is produced through the protonation of NH₃ which has the highest proton affinity of the neutral species and is therefore the terminal ion. The ratio of this species to the major ion species H₃O⁺ can then be an indicator of the importance of ion-neutral chemistry as an ion loss process compared to transport. We use data from the high resolution mode of the ROSINA (Rosetta Orbital Spectrometer for Ion-Neutral Analysis)/DFMS (Double Focussing Mass Spectrometer) instrument, which allows certain ions of the same integer mass per charge ratio to be separated from one another, most importantly H₂O⁺ and NH₄⁺. This data is then analysed alongside a range of plasma properties from the RPC (Rosetta Plasma Consortium) suite of instruments, to determine features of the plasma within and outside of the diamagnetic cavity that may systematically impact the ion species detected in the mass spectrometer, for example through the spacecraft potential.

For the same period, ion ROSINA/DFMS ion data are analysed together with simultaneous observations of the cometary plasma properties by RPC instruments, in order to identify systematic plasma features or biases which may impact the ion composition detected by ROSINA. In addition, the ion composition measurements are compared to ionospheric simulations. We evaluate the relative significance of ion-neutral chemistry and transport such that their impacts on the ion composition in different interaction regions are identified.

How to cite: Lewis, Z., Beth, A., Altwegg, K., Eriksson, A., Galand, M., Götz, C., Henri, P., Héritier, K., O'Rourke, L., Richter, I., Rubin, M., Stephenson, P., and Vallieres, X.: Ionospheric composition of comet 67P near perihelion with multi-instrument Rosetta datasets, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-960, https://doi.org/10.5194/epsc2022-960, 2022.

BepiColombo is a joint mission of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) to the planet Mercury. It was launched in October 2018 and it is due to arrive at Mercury in late 2025. It consists of two spacecraft, the Mercury Planetary Orbiter (MPO) built by ESA, and the Mercury Magnetospheric Orbiter (MMO) built by JAXA, as well as a Mercury Transfer Module (MTM) for propulsion built by ESA. The cruise phase to Mercury will last ~7 years and constitutes an exceptional opportunity for studying the evolution of the solar wind, solar transients, as well as for planetary science and planetary space weather. On this last topic, BepiColombo is proving to be an important upstream solar wind monitor for the terrestrial planets. This is especially important for case of Mars where we currently do not have many observations of the upstream interplanetary magnetic field or solar wind. As consequence, the analysis and interpretation of ionospheric observations is challenging, especially when coronal mass ejections and solar energetic particles hit Mars and we do not have Earth plasma observatories in good alignment with Mars to provide the space weather context. While Mars missions such as Mars Express or MAVEN are able to investigate the impact of the solar wind on the ionosphere, BepiColombo can be the solar wind sentinel for Mars, so we can see the cause and effect. Therefore, this work focuses on the response of the Martian ionosphere to solar transient events which have been previously detected by BepiColombo, and for which we can provide the right upstream solar wind context, such as during the last months of 2021. The objective is to evaluate the response of the Martian ionosphere and its dynamics with more accuracy knowing the exact energy inputs from the solar wind as detected in-situ in the solar wind by BepiColombo.

How to cite: Sanchez-Cano, B., Lester, M., Joyce, S., Witasse, O., Benkhoff, J., Heyner, D., Pinto, M., Moissl, R., and Vainio, R.: BepiColombo as upstream solar wind monitor for Mars’ ionosphere, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-994, https://doi.org/10.5194/epsc2022-994, 2022.

The Rosetta spacecraft followed comet 67P/Churyumov-Gerasimenko (67P) for more than two years, at slow walking pace (about 1 m/s) within 1500 km from the nucleus. During one of the radial movements of the S/C in the early phase of the mission the radial distribution of the plasma density could be estimated, and the ionospheric density was found to be inversely proportional to the cometocentric distance r from the nucleus (a 1/r-distribution). In this study we characterise the radial distribution of plasma around 67P throughout the mission further, and expanding on the initial results. We also investigate how a 1/r-distribution can be perceived during a flyby with a fast (10's km/s) spacecraft, such as the upcoming Comet Interceptor mission, when there is also an asymmetry introduced to the outgassing over the comet surface. We use data from the Rosetta Plasma Consortium (RPC) Langmuir probe (LAP) and Mutual Impedance (MIP) instruments during six  intervals throughout the mission, when Rosetta moved radially with respect to the comet, to determine the radial distribution of the plasma. We then simulate what radial distribution a fast flyby mission would actually observe during its passage through a coma when there is a 1/r plasma density distribution but also an asymmetric outgassing introduced. The plasma density around comet 67P is found to roughly follow a 1/r dependence, although significant deviations occur in some intervals. If normalizing all data to a common outgassing rate (or heliocentric distance) and combining the intervals to cover a the full radial range of 10-1500 km, a 1/r^1.19 average distribution is found. The simulated observed density from a fast S/C flying through a coma with a 1/r-distribution but with an asymmetric outgassing can in fact appear as both a 1/r-distribution, a 1/r^2-distribution, or an even steeper distribution, due to the combined effect of the radial variation in plasma with the variation in density arising from the spacecraft moving over an asymmetrically outgassing body.

How to cite: Edberg, N. J. T., Johansson, F. L., Eriksson, A. I., Vigren, E., Henri, P., and De Keyser, J.: Radial distribution of plasma at comet 67P and implications for cometary flyby missions, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-631, https://doi.org/10.5194/epsc2022-631, 2022.

Electron density structure and its temporal/spatial variations is one of the critical quantities in understanding an upper atmosphere. Mars has currently several orbiters studying its upper atmosphere and in particular electron density profiles.  The Mars Express (MEX), in the orbit since 2003 has been measuring Mars upper atmosphere through remote measurements by the MARSIS (Sub-Surface Sounding Radar Altimeter) sounder and radio occultations by MaRS (Radio Science Experiment - sounding of the internal structure, atmosphere and environment). The Mars Atmosphere and Volatile EvolutioN,  MAVEN mission  whose science objectives include exploration of the interactions of the Sun and the solar wind with the Mars magnetosphere and upper atmosphere has  complete plasma package. Maven has been performing in-situ composition measurements since November 2014, in particular, the Langmuir Probe and Waves  (LPW) instrument onboard MAVEN provide electron density using current-voltage sweeps.

Here we  present the comparison of multi-instrument spacecraft measurements of Mars upper atmosphere for selected dates, using remote sensing (MEX) and in-situ measurements (MAVEN).  The mutual observations are selected from publicly available data on ESA Planetary Science Archive as well as MAVEN Science Data Center. The L2 level Radio Occultation data are analyzed to obtain the Mars upper Atmosphere Electron density profiles. The MARSIS and LPW provide top side electron profiles whereas Radio occultations provide the full electron density profile. We focuse on the photochemical equilibrium region of the Martian ionosphere–thermosphere  below 200 km. The analysis  also includesz the  Deep Dip  campaigns of MAVEN making in-situ measurements of the region near the ionospheric peak.

The comparison of independent measurements using different techniques will be presented and the differences and similarities between the observations will be discussed to help to validate our understanding of the physical and chemical processes occurring in the atmosphere.

Figure 1: Comparison of MEX Radio Occultations (RO) with the MAVEN Langmuir Probe and Waves (LPW) for 3 selected mutual observation in March 2015

How to cite: Karatekin, Ö., Krishnan, A., Verkercke, S., Henry, G., Sánchez-Cano, B., and Witasse, O.: Multi-instrument/Spacecraft observations of Mars upper Atmosphere Electron density, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-688, https://doi.org/10.5194/epsc2022-688, 2022.

Radars in orbit around Mars such as MARSIS on Mars Express and SHARAD on Mars Reconnaissance Orbiter provide evidence for the nature of the surface and some sub-surface layers.  We have now extended our earlier work, which has indicated solar energetic particles are responsible for the attenuation of the reflected MARSIS and SHARAD radar signals from the surface of Mars, often resulting in radar blackouts. The MARSIS instrument also operates in a topside sounding mode, the Advanced Ionospheric Sounder AIS mode), which also receives surface reflections and we now investigate the impact of the solar energetic particles on the surface reflection during ionospheric sounding observations made by MARSIS. We present observations during two intervals in December 2014 and in September 2017. MARSIS AIS was making observations on the nightside as Mars Express moved towards periapsis and then towards the dayside. The nightside AIS observations clearly demonstrate a similar loss of the surface signal to that seen in the MARSIS sub-surface mode. In addition there is evidence of a reflection from the enhanced layer created by the electrons which is responsible for the attenuation in the signal. The critical frequency is of order 1 MHz, which is equivalent to a peak electron density of order 10¹⁰ m^-3, at an altitude of about 100 km. These characteristics are similar to our previous modelling work of the impact of the solar energetic electrons.

How to cite: Lester, M., Sanchez-Cano, B., Joyce, S., Meggi, D., Opgenoorth, H., Lillis, R., Witasse, O., Orosei, R., and Cartacci, M.: Radar Blackouts at Mars: Evidence for a low altitude ionisation layer, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1040, https://doi.org/10.5194/epsc2022-1040, 2022.

Global dust storms at Mars engulf the entire planet in a dusty haze, causing increases in temperature and ion escape as dust is lifted up to 80 km in altitude. The two most recent storms occurred in 2007 (Mars Year (MY) 28) and 2018 (MY34), and have been observed by spacecrafts such as Mars Express (MEx). MEx has been operating at Mars since 2004, and has produced a long time-base of plasma measurements from as low as 250 km. Using MEx, we investigate whether the 2007 dust storm has influenced the magnetosphere of Mars by looking at the position of the bow shock and induced magnetospheric boundary, compared to the expected position provided by 3D magnetohydrodynamical models. To identify boundary positions, we use data from the ASPERA-3 instrument (Analyser of Space Plasma and EneRgetic Atoms) onboard MEx, which contains an electron spectrometer (ELS), ion mass analyser (IMA), neutral particle imager (NPI) and neutral particle detector (NPD). For this study, we use data from ELS and IMA. We consider a number of influences on the boundary position, including the solar wind conditions and the crustal fields. Our study period includes time before, during, and after the MY28 global storm, and we expected the bow shock and induced magnetospheric boundary to increase in altitude due to the storm. Out results show that the system is more complex, and multiple influences need to be distinguished to leave any change due to the dust storm itself.

How to cite: Regan, C., Coates, A., Wellbrock, A., Haythornthwaite, R., Jones, G., Sánchez-Cano, B., Holmström, M., Frahm, R., and Garnier, P.: Investigating the Global Dust Storm in Mars Year 28 with Mars Express, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-527, https://doi.org/10.5194/epsc2022-527, 2022.

Space weather events are one of the many major factors affecting the escape and evolution of Martian atmosphere. The Sun-planet interaction is affected by several factors such as the heliocentric distance, chemical composition of the atmosphere, solar illumination and its intrinsic magnetic field. Mars has a varied environment of magnetic field. It has little or no intrinsic magnetic field, but there exist some strong, crustal magnetic field patches. Thus, it becomes one of the solar system's best models for understanding the interaction of weakly ionized plasma with a highly irregular magnetic field.

Martian ionosphere owes its existence to the photoionization of neutral species by solar extreme ultraviolet (EUV) and X-ray photons. Martian ionosphere has a stratified structure with two main layers in its electron density profile (N_e). The primary layer (M2 layer) is formed by solar EUV radiation (~20-90 nm) and has a peak electron density at around 120-140 km altitude with a peak density of ~10¹¹ m^-3. The second layer (M1 layer) occurs at lower altitude with a peak electron density of ~10⁹ m^-3 and is formed by solar soft X-ray and electron impact ionization. The electron densities and the altitudes at which these peaks are very variable.

Radio Occultation (RO) experiments are the first and major explorer of the Martian ionosphere and electron density profiles. RO experiments precisely measure the Doppler shift observed on the link between a planetary spacecraft and Earth, as the spacecraft passes into occultation behind the planet. The RO data can be processed to extract the vertical electron density profiles of the ionosphere. Apart from vertical electron density profiles, RO can also provide density, temperature and pressure profiles of the neutral atmosphere. Thus, it is also a powerful tool to understand the both the neutral atmosphere and ionosphere.

Here we study the effect of solar flares and coronal mass ejections on the whole Martian atmosphere using the publicly available Mars Express radio occultation data from ESA Planetary Science Archive (PSA). For this, we selected two major solar disturbed periods occurred during 6^th to 13^th of June 2011 and 16^th February to 31^st March 2015. Using the Level 2 data we calculated the N_e profiles in the ionosphere as well as the temperature profiles of lower atmosphere. We also compare our results with numerical models and available measurements like MARSIS and Langmuir probe on NASA's MAVEN in the selected period.

Figure 1: a. Electron density profiles observed by MEX on 2011 following a solar event on the 8^th of June 2011.

How to cite: Krishnan, A., Karatekin, Ö., Verkercke, S., Henry, G., and Witasse, O.: Effect of Solar Event on Mars Atmosphere, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-673, https://doi.org/10.5194/epsc2022-673, 2022.

The Martian magnetosphere contains elements of induced and intrinsic origin.  We will focus on three questions concerning its structure. Reconnection of the draping IMF with crustal field leads to a twisting of classical induced configuration. Why this twist is so stable and well arranged despite of a very complex topology of the crustal magnetic field.  Another interesting question is a significant asymmetry of the Martian magnetosphere. The observations show that additionally to the main draping of the interplanetary magnetic field lines in the antisunward direction a draping in the opposite direction to the motional electric field arises. What origin is of such asymmetry? The third question is related to the fact that Mars occurs not only in the flow of solar wind but also in the flow of ‘oxygen wind’ originating from the extended hot oxygen corona. What effects arise during such type of the interaction? We will discuss possible answers on these questions.

How to cite: Dubinin, E., Fraenz, M., and Paetzold, M.: Do we understand well how the Martian magnetosphere is organized?, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-71, https://doi.org/10.5194/epsc2022-71, 2022.

We estimate ion escape from Mars by combining 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 results in different amounts of mass loading of the solar wind. Then we obtain the ion escape rate from the model run that best fit observations of the bow shock location. This method 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. This approach also allows us to use data sets traditionally not used for ion escape estimates, such as magnetic field and electron observations. We can also estimate the escape rate from a very small set of observations, during every orbit of a spacecraft around a planet or during one flyby of a planet.

How to cite: Holmstrom, M., Zhang, Q., Wang, X.-D., and Fatemi, S.: Estimations of Ion Escape from Mars, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-239, https://doi.org/10.5194/epsc2022-239, 2022.

The Rosetta spacecraft escorted comet 67P/Churyumov-Gerasimenko for two years along its orbit, from Aug 2014 to Sep 2016, observing the evolution of the comet from a close perspective. The Rosetta Plasma Consortium (RPC) monitored the plasma environment at the spacecraft throughout the escort phase.

Cometary electrons are produced by ionization of the neutral gas coma. This occurs through photoionization by extreme ultraviolet photons, and through electron-impact ionization (EII) by collisions of energetic electrons with the coma. Far from perihelion, EII is, at times, more prevalent than photoionization (Galand et al., 2016; Heritier et al., 2018), but the EII frequency has not been assessed across the whole mission. The source of the cometary electrons, and the origin of the ionizing electrons is still unclear.

We have calculated the electron impact ionization (EII) frequency throughout the Rosetta mission and at its location from measurements of RPC’s Ion and Electron Sensor (RPC/IES). EII ionization is confirmed as the dominant source of cometary electrons and ions when far from perihelion but is much more variable than photoionization. We compare the EII frequency with properties of the neutral coma and cometary plasma to identify key drivers of the energetic electron population. The EII frequency is structured by outgassing rate and magnetic field strength.

The first 3D collision model of electrons at a comet (Stephenson et al. 2022) is also utilised to assess the origin of electrons within the coma. The model uses self-consistently calculated electric and magnetic fields from a fully-kinetic and collisionless Particle-in-Cell model (Deca et al. 2017, 2019)as an input. The modelling approach confirms cometary electrons are produced by impacts of energetic electrons at low outgassing. The ionizing electrons are identified as solar wind electrons that have undergone acceleration in an ambipolar potential well, confirming the results of the data analysis.

Deca J, Divin A, Henri P, Eriksson A, Markidis S, et al. 2017. Physical Review Letters. 118(20):205101
Deca J, Henri P, Divin A, Eriksson A, Galand M, et al. 2019. Physical Review Letters. 123:55101
Galand M, Héritier K L., Odelstad E, Henri P, Broiles TW., et al. 2016. Monthly Notices of the Royal Astronomical Society. 462:S331–51
Heritier KL, Galand M, Henri P, Johansson FL, Beth A, et al. 2018. A&A, p. 618:A77–A77
Stephenson P, Galand M, Deca J, Henri P, Carnielli G. 2022. Monthly Notices of the Royal Astronomical Society. 511(3):4090–4108

How to cite: Stephenson, P., Altwegg, K., Beth, A., Burch, J., Carr, C., Deca, J., Eriksson, A., Galand, M., Glassmeier, K.-H., Goetz, C., Henri, P., Heritier, K., Johansson, F., Lewis, Z., Nilsson, H., and Rubin, M.: The source of electrons at a weakly outgassing comet, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1047, https://doi.org/10.5194/epsc2022-1047, 2022.

The Imaging Ultraviolet Spectrograph (IUVS) on the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has been used to observe the Mg+ in the upper atmosphere of Mars since 2015. These observations reveal significant diurnal, seasonal and latitudinal variations. For example, a factor of two change in Mg+ occurs during the day at the equator and Mg+ above 100 km decreases across the globe during the Southern Hemisphere summertime.  Possible causes include the influence of photo-chemistry, atmospheric dynamics and the injection rate of meteoric material. To delineate these sources of variability, a 3-dimensional model of the Martian Mg has been developed. The model is based on the Laboratoire de Météorologie Dynamique (LMD) Mars global circulation model (GCM), which is capable of simulating the seasonal cycles in the Martian atmosphere arising from changes in heating rates from orbital geometry and the distribution of dust in the lower atmosphere. The model solves for the dynamics and primary constituents of the atmosphere from the surface to the thermosphere. For this study, the chemistry has been augmented with neutral and ion chemistry for meteoric metals within a CO2 atmosphere, incorporating 7 neutral and 8 ionized Mg-containing species and an additional 42 neutral and ion-molecule reactions. The atmospheric input of meteoric material is specified from seasonal and latitudinal fits to new estimates of the deposition of the ablated metals in the atmosphere. Here we present the first detailed intercomparison of the MAVEN IUV Mg+ observations with simulated Mg+ from the LMD Mars GCM. Model variability is consistent with observations and indicates tropical variability is caused by a combination of photochemistry and vertical transport by atmospheric tides. Comparisons of simulations performed with variable and fixed meteoric input show that the high latitude variations are caused by both seasonal variation in ablation rates and the residual circulation. Finally, we show how Mg+ varies in relation to neutral Mg and the remaining Mg-containing species to determine how Mg+ may be used as a proxy for total Mg variability.

How to cite: Marsh, D., Feng, W., Plane, J., Carrillo-Sánchez, J. D., Janches, D., Crismani, M., Chaufray, J.-Y., Forget, F., González-Galindo, F., and Schneider, N.: Martian Meteoric Mg+: an intercomparison of MAVEN/IUVS observations with simulations using the LMD Mars GCM, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-644, https://doi.org/10.5194/epsc2022-644, 2022.

An investigation of the locations where the bulk thermal pressure is balanced by magnetic pressure in the Martian ionosphere is reported on. We present a statistical study in which we characterize the location where the plasma and magnetic pressures are equal to one another. The data, recorded by the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, have been analyzed from the transition altitude in which the ionospheric ions become magnetized, up to an altitude of ~800km. The electron temperature and density measurements for the plasma thermal pressure were made by the Langmuir Probe and Waves (LPW) instrument, and the magnetic field strength for determining the magnetic pressure was measured by the Magnetometer (MAG) instrument. The three major trends in this pressure balance are: (a) the magnetic pressure is always larger, (b) a clear transition at low altitudes from thermal pressure to magnetic pressure is observed, and (c) the dominant pressure is changing back and forth between the two over a range of altitudes. The findings are studied in congruence with orbital parameters of the MAVEN satellite (including solar local time, latitude, location with respect to crustal fields) to divulge possible explanations of the transition between pressures.

How to cite: Shaver, S., Andersson, L., and Thaller, S.: Locations where the cold thermal pressure balances the magnetic pressure in the Martian ionosphere, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-552, https://doi.org/10.5194/epsc2022-552, 2022.