TP5
This session focuses on the ionospheres of Mars, Venus, Pluto, Titan, and comets, and solicits abstracts concerning remote and in situ data analysis, modelling studies, instrumentation and mission concepts. Abstracts on planetary flybys, such as the BepiColombo and Solar Orbiter flybys to Venus, are also welcome. Topics may include, but are not limited to, day and night side ionospheric variability, sources and influences of ionization, ion-neutral coupling, current systems, comparative ionospheric studies, and solar wind-ionosphere interactions and responses of the ionized and neutral regimes to transient space weather events. Abstracts on general plasma and escape processes are also welcome.
The Venus and Mars interactions with the solar wind are often compared because both planets lack a substantial intrinsic global magnetic field, and both have CO2-dominated atmospheres thick enough to form an ionosphere (ionized atmospheric layer). To first order, their magnetospheres are mainly induced in nature, with draped interplanetary magnetic fields (IMF) dominating their topology. However, this simple picture can be complicated by the magnetization of the ionosphere at Venus and Mars’s localized crustal field magnetism. An important property of these planet-solar wind interactions is the magnetic field’s connectivity to the collisional ionosphere/atmosphere, and possibly the planet surface. This can provide insights into the induced magnetization state of their ionospheres, the possible particle and energy exchange between their ionospheres and the solar wind, and the impact Mars’s crustal fields have on its near-space environment. Suprathermal (>1 eV) electrons are easily magnetized and excellent tracers of magnetic topology. In this talk, we describe the use of combined electron energy and pitch angle distributions measured by Venus Express and Mars Atmospheric Volatile and EvolutioN (MAVEN) to infer magnetic topology at Venus and Mars, respectively. We will review the main contributions of magnetic topology to the understanding of the Mars and Venus plasma environment.
How to cite: Xu, S.: Magnetic Topology at Mars and Venus, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-53, https://doi.org/10.5194/epsc2024-53, 2024.
The study explores the dynamic interaction between Interplanetary coronal mass ejections (ICMEs) and the induced magnetosphere of Venus, utilizing measurements from the Venus Express (VEX) mission. Over the period 2006-2013, we analyzed 16 ICME events, noting peak magnetic field strengths at the ionopause around 100 nT. Our investigation comprehensively examines the altitude of the inbound bow shock and ionopause during these ICME passages. The ionosphere is found to be highly magnetized due to the very high magnetic pressure of the induced magnetosphere. Remarkably, the altitude of the ionopause is found to be significantly compressed as compared to the previous quiet day due to the increased solar wind dynamic pressure. Intriguingly, the bow shock position exhibited minimal deviations compared to typical quiet days, underscoring that, during ICME events, the ionopause location is more responsive to solar wind pressure fluctuations than the bow shock location. Additionally, we observed a notable increase in heavy-ion density near and above the ionopause compared to quiet days. This substantial increase implies that ICMEs can induce atmospheric loss in Venus’s atmosphere and also cause a significant reduction in the ionopause location.
How to cite: Rout, D., Thampi, S., Miyoshi, Y., Pant, T., and Bhardwaj, A.: The response of the Venusian upper atmosphere during the passage of interplanetary coronal mass ejections, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-259, https://doi.org/10.5194/epsc2024-259, 2024.
When the cone angle of the solar interplanetary magnetic field (IMF) becomes small, induced magnetospheres of unmagnetized planets degenerate, resulting in a markedly different mode of the interaction. In this case, solar wind protons penetrate all the way to the top of the atmosphere on the dayside of Mars. Ions from the ionosphere propagate upstream in the solar wind, toward the Sun, with a substantial flow perpendicular to the solar wind flow. We investigate the ionospheric ion escape from such an object. This study specifically concentrates on hybrid simulations of the ionospheric ion escape from Mars in the case of the 4° cone angle with the other solar wind conditions typical. The total escape rate is found to be almost one order of magnitude higher than for the typical Parker spiral case. The unique feature of the degenerate induced magnetosphere is the upstream escape driven by the ambipolar field, contributing 42% to the total escape rate, fully absent in the Parker spiral case. Additionally, 52% of the total escape occurs through the cross-flow plume, arising from the drift of ionospheric ions in the weak convective field and IMF. This channel dominates and is seven times more intense than the plume driven by the convective field in the nominal case. Understanding how degenerate magnetospheres operate is important not only for the planets in the solar system, but also for exoplanets.
How to cite: Zhang, Q., Barabash, S., Holmström, M., Wang, X.-D., Futaana, Y., Fowler, C. M., Ramstad, R., and Nilsson, H.: Ion escape from degenerate induced magnetospheres: The case of Mars, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-91, https://doi.org/10.5194/epsc2024-91, 2024.
Introduction
Auroras are hallmarks of the interaction between solar particles and the atmosphere of planets. Martian aurora was first discovered in 2005, since then, four different types have been identified: localized discreet aurora (Bertaux et al., 2005), global diffuse aurora (Schneider et al., 2015), dayside proton aurora (Deighan et al., 2018), and large-scale sinuous aurora (Lillis et al., 2022). All previous detections have been made in the UV from orbit. Here we present, from observations with the SuperCam and MastCam-Z instruments on the Mars 2020 Perseverance rover, the first detection of aurora from the Martian surface and the first detection of the green 557.7 nm atomic oxygen auroral emission on Mars. This is the same emission line that is familiar from terrestrial aurora.
Charged particles accelerated by interplanetary coronal mass ejections (ICMEs) or solar flares are referred to as solar energetic particles (SEPs) (Reames, 1999). Diffuse aurora is strongly correlated with SEP events. ICME-accelerated SEPs travel nearly radially, as opposed to flare-accelerated SEPs which follow the Parker spiral. If the solar source region is identified, ICME-accelerated SEP events at Mars, and thus diffuse aurora, can be forecasted.
The dynamic nature of rover planning and operations allows for a reactive observation strategy that takes advantage of such forecasts. We made several attempts, starting in May 2023, to react to SEP events and observe with the M2020 rover (Farley et al., 2020) instruments at times when we believed the likelihood of emission to be highest. Our fourth attempt, in March 2024, yielded the positive detection reported here.
Instruments
On the M2020, SuperCam and MastCam-Z have the best combination of sensitivity and operational flexibility for detecting diffuse aurora.
SuperCam is a multi-technique spectrometer. Its channel covering the 535-853 nm range includes an optical intensifier which can amplify weak optical signals (Wiens et al., 2021) and therefore make auroral emissions, especially the atomic oxygen forbidden transitions at 557.7 and 630 nm, detectable. Other channels lack an intensifier and therefore the UV emissions commonly seen in Mars aurora (e. g. (Schneider et al., 2015)) are not expected to be detectable.
MastCam-Z is a pair of multispectral, stereoscopic imaging cameras capable of providing broadband and narrowband color images, and direct solar images using neutral density filters. Each camera has a CCD detector with 1648×1214 pixels with a selectable field of view ranging from 6.2°×4.6° to 25.6 ×19.2° (Bell et al., 2021).
Results
On March 15th 2024, a long-lasting C4.9 flare with an accompanying ICME erupted from Active Region 13599. Mars was expected to be centered in the projected path, with ion density peaking around 04:00 UTC, March 18th.
Error Detection And Correction (EDAC) counters are cumulative housekeeping logs, registering bit-flips in spacecraft memories. EDACs are sensitive to SEP events, which manifests as jumps in the otherwise steadily increasing counter. Mars Express logged 4 times as many errors when the ICME was expected to reach Mars compared to before and after the solar storm, as indicated in Figure 1.
Figure 1: Housekeeping error log from Mars Express during the six week interval surrounding the March 18th event. The blue line shows the cumulative errors, the orange line shows the number of errors per day, and the green line indicates the time of the rover observations.
SuperCam and MastCam-Z observations were scheduled shortly after the predicted ion density peak. The SuperCam observation consisted of 2x75 spectra and began at 00:33 local mean solar time (LMST) on Sol 1094, or 06:47 UTC on March 18. Figure 2 shows an average of all spectra, after detector background subtraction, and further processing with a 3-pixel-wide median filter. Fitting a gaussian line-shape (0.452 nm FWHM) and 3rd-order polynomial continuum, we obtain 93 R for the 557.7 nm auroral emission with a 1-σ uncertainty of 13 R (Rayleigh is a photon flux, where 1 R corresponds to a column emission rate of 1010 photons per square metre per column per second). No other emission lines were observed. From preliminary radiative-transfer modeling, using an adapted version of the multiple-scattering pseudo-spherical code of Clancy et al., (2017), we estimate that the intensity would have been 1.9 kR if viewed on the limb from orbit.
MastCam-Z imaged the sky using filter position 0 in both cameras starting at 00:43 LMST. Although sky brightness was dominated by Phobos-illuminated aerosols leading to an overall yellow-orange color, after modeling and subtracting the Phobos light we found an excess green-channel signal equivalent to 100 +/- 20 R, fully consistent with the green line emission detected by SuperCam.
Figure 2: SuperCam spectra and best-fit model. Top panel: the average of 2x75 spectra shown in black, and best-fit model shown in green. Bottom panel: residual shown in red.
Summary and discussion
A green atmospheric emission was observed by the M2020 rover on March 18th 2024. The signal observed by SuperCam and MastCam-Z corresponds to an intensity of around 93 R. The observed event was likely associated with a C4.9 flare and a subsequent ICME. Considering that the particle flux increase observed in orbit coincided with the estimated arrival of the ICME, we conclude the observed diffuse aurora was mainly induced by ICME-accelerated SEPs.
This detection confirms the prediction from UV observations that emissions would also occur at optical wavelengths. This opens a new avenue for the study of space weather events at Mars. Optical instruments are simpler and cheaper than the UV instrumentation used to date. While the brightness of this event was dimmed by dust, events under better viewing conditions or heavier particle precipitation would likely be above the threshold for human vision and visible to future astronauts.
Acknowledgements
We thank Olivier Witasse for providing EDAC data, and NASA’s Mars Exploration Program for support. We acknowledge the Community Coordinated Modeling Center at Goddard Space Flight Center for the use of the DONKI tool, https://kauai.ccmc.gsfc.nasa.gov/DONKI/, and the Mars Space Weather Alert Notification system which notified us of the SEP event.
How to cite: Knutsen, E. W., McConnochie, T. H., Lemmon, M., Tamppari, L., Viet, S., Cousin, A., Wiens, R. C., Francis, R., Donaldson, C., Lasue, J., Forni, O., Patel, P., Schneider, N., Carrasco, D. T., and Palacio, V.: First detection of visible-wavelength aurora on Mars, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-767, https://doi.org/10.5194/epsc2024-767, 2024.
The Rosetta spacecraft accompanied comet 67P/Churyumov-Gerasimenko for about two years as the comet approached the sun, passed through perihelion, and headed outwards in the solar system again. The activity level of the comet increased when the distance to the sun decreased and a cometary magnetosphere was born. Different plasma boundaries formed, separating distinct regions, such as the diamagnetic cavity or the solar wind ion cavity. A fully developed bow shock was never observed, as the spacecraft spent most the time close to the nucleus. Instead, measurements revealed what appeared to be the first stages of the formation of shock: the infant bow shock. A characteristic feature of the observations of the infant bow shock is the change of the solar wind proton velocity distribution from fast and cold to slow and warm. Such transitions of the solar wind proton populations have been observed many times at comet 67P.
In this paper we focus on the details of the proton velocity distribution functions during apparent transitions between cold and warm protons. It is not obvious how the distributions look like. Protons that appear warm and slow in an energy-time spectrogram may instead be a (partial) ring distribution. Partial ring distributions were not expected at comet 67P due the small spatial scales but were recently reported. Both solar wind proton and cometary ions seem, at least occasionally, to form partial ring distributions in the cometary environment. We study the shape of the velocity distribution functions during cold proton-warm proton-transitions to confirm or reject the interpretation of the warm protons as an indication of an infant bow shock. We also try to understand the physics behind the change of the velocity distribution and, if applicable, the formation of the infant shock.
How to cite: Stenberg Wieser, G., Moeslinger, A., Nilsson, H., Gunell, H., and Goetz, C.: What can velocity distribution functions of warm protons at comet 67P tell us about infant bow shocks?, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-270, https://doi.org/10.5194/epsc2024-270, 2024.
The interaction of Titan's ionosphere with Saturn's magnetosphere results in a complex region of perturbed magnetic fields, energetic and thermalized electrons and ions-induced magnetosphere (IM). Although the complexity of IM has been mentioned before, the local structure hasn't been investigated widely in the past years. In this case study we examine the origin of periodic electron plasma structures in Titan's induced magnetosphere observed during the T36 flyby. We use data from the electron and ion spectrometers CAPS/ELS and IMS, the Langmuir probe and electric antenna RPWS/LP, and the fluxgate magnetometer FGM to analyze plasma parameters, e.g. density and temperature, magnetic field fluctuations. The observed electron structures are periodic on a scale of ~ 20 seconds and possess signatures of acceleration from a few eV up to 700 eV. At the same time, the burst of low-frequency (around the ion-cyclotron and lower-hybrid frequency) and low-amplitude (~ 1 nT ) waves is observed. We propose that the observed electron structures are the result of a large-scale MHD instability as well as could possibly be a generic feature of Titan's induced magnetosphere structure.
How to cite: Kim, K., Edberg, N., Coates, A., and Modolo, R.: The electron structures in Titan’s induced1magnetosphere observed during the T36 flyby, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-334, https://doi.org/10.5194/epsc2024-334, 2024.
New Horizons observations show an extensive depletion region at Pluto’s wakeside as a result of the interaction of heliospheric ions with Pluto’s induced magnetosphere. This rarefaction arises despite the ions having gyroradii multiple orders of magnitude greater than the dwarf planet’s radius. The interaction is studied by employing an energetic particle tracing tool in conjunction with electromagnetic field output from a hybrid plasma simulation of Pluto’s interaction region. The tracing of incident heliospheric ions across a range of energies will be used to analyze the deflection mechanisms responsible for the formation of this depleted region at Pluto’s wakeside.
Additionally, periodic variations in energetic ion flux have been identified within the wake region. We investigate whether particle deflection as a result of the field from bi-ion waves produced by the shear flow between solar wind and pick-up ions can explain the periodicities observed in the wake.
How to cite: Ruch, R., Simon, S., and Haynes, C. M.: Energetic Ion Dynamics in Pluto's Induced Magnetosphere, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-27, https://doi.org/10.5194/epsc2024-27, 2024.
INTRODUCTION
Venus lacks an intrinsic magnetic field, exposing its upper atmosphere directly to the solar wind. The solar Extreme UltraViolet (EUV) radiation ionizes the upper layer of the atmosphere, known as the ionosphere, which in turn deflects the solar wind around the planet, resulting in the formation of an induced magnetosphere (Futaana et al., 2017). The induced magnetosphere contains different plasma boundaries, for example, the bow shock (BS), where the solar wind is slowed, heated and deflected as it transitions from the supersonic and super-Alfvénic regime to the subsonic and sub-Alfvénic regime. Another boundary, the ion composition boundary (ICB) marks the separation between solar wind and planetary ions (e.g., Martinecz et al., 2008)
The Pioneer Venus Orbiter (PVO) and Venus Express (VEX) missions have provided insights into Venus' plasma environment (e.g., Phillips et al., 1991; Svedhem et al., 2007). Data from these missions reveal that the boundaries of Venus' plasma environment vary in response to various upstream conditions. The BS and the ICB are influenced by the solar cycle phase, the magnetosonic Mach number, the solar wind dynamic pressure, and the Interplanetary Magnetic Field (IMF) direction and magnitude (e.g., Alexander et al., 1985; Russell et al., 1988; Zhang et al., 1991; Russell et al., 2006). In this study, we seek to develop refined boundary models which take into account upstream conditions.
DATASET AND METHOD
To characterize the Venus-solar wind interaction, the key information is how the boundaries' positions depend on various solar wind parameters. Formulating these variations in analytical form allows us to predict their positions. We used boundary crossings and upstream conditions recorded by the ion mass analyzer (IMA), the electron spectrometer (ELS), and the magnetometer (MAG) onboard VEX (Signoles et al., 2023) (Figure 1). We modelled the BS with a conic section curve, symmetrical around the longitudinal axis, expressed by
d = L / (1 + εcosα),
where d and α are the radial and angular coordinates, respectively. The semi-latus rectum L and the eccentricity ε are the free parameters, and we investigated their dependencies on upstream conditions. We also characterized the dayside ICB with a half sphere with radius ρ as free parameter. The nightside ICB is instead best modelled with a linear relation (eg., Martinecz et al., 2008). However, the higher number of crossing points on the dayside (Figure 1) restricted which characteristics of the boundaries we could study. The eccentricity ε in the BS model mainly affects the nightside flaring angle, so we couldn't reasonably investigate its dependence on upstream conditions. Therefore, our study focused solely on variations in L. Additionally, we didn't have enough crossings to model the nightside ICB, so we only considered the dayside portion.
Figure 1: The BS and ICB positions and shapes. The X-axis points in the Sun direction, while R=(Y2 + Z2)1/2. The outer and inner curves represent the BS and ICB derived in this study, respectively. The boundaries' free parameters for the general models are L= 1.525 RV (Venus radius), ε = 1.036 and ρ = 1.122 RV. The BS focus is at x0 = 0.688 RV.
RESULTS AND DISCUSSION
Figure 1 shows the crossing points used in this study and the obtained BS and ICB models using the whole dataset. We further studied the free parameters' variation with different upstream conditions. Figure 2 shows an example of the L variation with IMF magnitude B and mass flux p.
Figure 2: The BS semi-latus rectum L as a function of IMF magnitude and mass flux. Each dot represents a data bin, containing several crossings. The horizontal bars represent the variability of the upstream conditions in each bin and the vertical bars represent the standard errors on L. The quantities are normalized by their average values.
We developed our final BS and ICB model by combining upstream conditions that minimized errors in predicting the boundaries' positions and shapes. In the BS model, the parameter L exhibits a linear dependence on the IMF magnitude and the shock normal angle θbn, while it inversely correlates with the mass flux. The shock normal angle is the angle between the IMF direction and the local shock normal at the crossing point. The ICB model depends linearly on the EUV flux FEUV and is inversely proportional to the energy flux FE. The models improve the accuracy of predicting boundary positions by approximately 22% for the BS and 8% for the ICB, compared to statistical models which disregard upstream conditions. Our findings indicate that the BS is more variable than the ICB as well as more sensitive to upstream conditions. Our conclusions agree with previous studies which suggest that the boundaries are influenced by the IMF, the solar wind dynamic pressure and the solar flux (e.g., Alexander et al., 1985; Russell et al., 1988; Zhang et al., 1991; Russell et al., 2006). Moreover, the shock normal angle dependence creates a quasi-perpendicular/quasi-parallel BS asymmetry. The quasi-parallel side of the BS (θbn< 45°) tends to be closer to the planet compared to the quasi-perpendicular side (θbn > 45°). This behaviour was confirmed in other studies as well (Zhang et al., 1991; Chai et al., 2014; Signoles et al., 2023).
REFERENCES
Alexander, C. J. et al. 1985, Geophys. Res. Lett., 12, 369
Chai, L. et al. 2014, JGRA, 119, 9464
Futaana, Y. et al. G. J. 2017, SSRv, 212, 1453
Martinecz, C. et al. 2008, PSS, 56, 780
Phillips, J. L. et al. 1991, SSRv, 55, 1
Russell, C. T. et al. 1988, JGRA, 93, 5461
Russell, C. T. et al. 2006, PSS, 54, 1482
Signoles, C. et al. 2023, ApJ, 954, 95
Svedhem, H. et al. 2007, PSS, 55, 1636
Zhang, T.-L. et al. 1991, Geophys. Res. Lett., 18, 127
How to cite: Rollero, U., Futaana, Y., and Rojas Mata, S.: Comprehensive Venus boundaries model, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-80, https://doi.org/10.5194/epsc2024-80, 2024.
Issues related to the fluid dynamic behavior of the solar wind as a continuum gas emitted from the sun have led to an increasing number of phenomena related to its motion, and distribution through the solar system. Among them it has been necessary to provide a source that justifies the continuum response of its particles as they expand from the sun with continuously decreasing densities. As such, it is convenient to point out that their ability to interact among them through particle-particle collisions strongly decreases as they move away from the sun. As a result, conditions without that quality should be rapidly encountered thus diminishing the manner in which the solar wind behaves as a continuum. Different from reaching planetary magnetic fields conditions are encountered whre the solar wind interacts with non-magnetic planets (Venus, Mars).. In such case the solar wind conducts a turbulent stochastic interaction that force strong oscillations ( Pérez-de-Tejada, 2024). Such conditions have not been resolved and require further analysis with calculations of parameters that are involved in the interaction process. In the data analysis presented below we will derive values for the mean free path of wave-particle interactions implied by the transport coefficients that are suitable to turbulent plasmas.
While there have been adequate efforts to examine plasma motion produced by instabilities in the complex mixture of solar wind and planetary ion particles there are issues that have not yet been suitably considered. In particular, the effects of dissipative phenomena to their motion together with the manner in which they transfer statistical properties have not been properly explored. Interest in this respect was advanced by Liepmann and Roshko (1967) who proposed a technique adequate to the kinetic theory of gases and that can be applied to examine the conditions in the solar wind interaction with planetary ionospheres.
A correlation between a suitable wave-particle interaction mean free path value λ and the kinematic viscosity and thermal conduction coefficients ν and k in a gas was derived by Liepmann and Roshko (1967) by using dissipation processes in the gas kinetic equations:
ν = vT λ for viscous dissipation (1)
vT λ = α k/ρcp for thermal dissipation (2)
where ρ and cp are the fluid density and its specific heat at constant pressure, and that were later employed by Pérez-de-Tejada (2024) in an analysis of the solar wind interaction with the Venus ionosphere that led to estimate λ values in terms of the ν and k coefficients.
A complementary analysis of that calculation will be conducted to explore the implications of considering varying values of the thermal speed vT of the solar wind and those of the kinetic viscosity coefficient ν. In particular, it can be noted in equation (1) that the λ value is inversely corelated to the thermal speed vT (60 km/s–100 km/s) of the solar wind in the Venus ionosheath where there are strong magnetic field fluctuations and that are available from the Mariner 5 spacecraft plasma data reproduced in Figure 1. In addition, by using the ν = 3 105 km2/s value of the kinematic viscosity coefficient derived from the momentum equation of the solar wind within a viscous boundary layer at and downstream from the Venus ionosphere (Pérez-de-Tejada, 1999) it is possible to estimate from equation (1) that λ is in the 103 - 104 km range that is comparable to the (~ 6 103 km) scale size of the Venus wake. In addition to evidence of the strong magnetic field fluctuations indicated in the Venus inner ionosheath in Figure 1 there is further support for such variations from the plasma measurements reported in the plasma data of the Venera spacecraft. In this case there is evidence that the plasma temperature and the bulk flow speed experience distinct and frequent variations between labels 2 and 3 in the Venus inner wake which are reminiscent of those shown in Figure 1. As a result, the flow behavior reveals turbulent conditions that are peculiar of the solar wind as it streams around the Venus ionosphere. The λ values derived above are indicative of the mean free path values that are required to justify that behavior. In particular, smaller λ values should be expected in the inner regions of the ionosphere where vT shows larger values that lead to more notable turbulent conditions.
Figure 1. (lower panel) Trajectory of the Mariner 5 spacecraft projected in cylindrical coordinates in its flyby past Venus. The labels 1 through 5 along the trajectory mark important events in the plasma properties (a bow shock is identified at features 1 and 5), the intermediate plasma transition occurs at features 2 and 4). (upper panel) Magnetic field intensity and its latitudinal and azimuthal orientation, together with the plasma properties (thermal speed, density and bulk speed) that were measured around Venus (Bridge et al., 1967).
On the other hand, larger λ values could also be obtained far away from the interaction region where smaller thermal speeds are available in terms of the same ν value used by Pérez-de-Tejada (2024). For example, if vT = 10km/s had been revealed in Figure 1, and we had applied the same ν = 3 105 km2/s value of the kinematic viscosity coefficient, equation (1) would now have led to λ ≈ 2 104 km which is larger than the width of the interaction region. A description of this variation was depicted by Pérez-de-Tejada (2024) to illustrate the manner in which λ varies as a function of vT for the ν = 3 105 km2/s value derived before. As a whole it is expected that λ ≥ 103 km with small values expected in the Venus inner ionosheath where vT is larger.
Liepmann J, and A. Roshko, Elements of Gasdynamics, John Wiley, 1967 (p.372); Pérez-de-Tejada, H., ApJ, 525, L65, 1999; Wave-particle interactions in Astrophysical plasmas, Galaxies, 2024 (In Press); Bridge et al., Science,158, 1669, 1967.
Pérez-de-Tejada, H., Vortex structures in planetary plasma wakes, Cambridge Scholars Pub. ISBN (10):1-5275-0110-8, 2023.
How to cite: Pérez-de-Tejada, H.: Mean free path values in wave-particle interactions of the solar wind with the Venus ionosphere , Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-148, https://doi.org/10.5194/epsc2024-148, 2024.
We present findings from the several flybys made by the Solar Orbiter, BepiColombo, and Parker Solar Probe missions, aimed at investigating the structure and dynamics of Venus' magnetotail. Our study focuses on the interplay between Venus' plasma environment and the solar wind, which shapes the induced magnetosphere. By analyzing magnetic field and plasma density data, we determine the spatial reach and behavior of Venus' magnetotail, and in particulat focus on the time and location of plasma boundary crossings. Notably, we observe significant differences in boundary crossing positions and characteristics across different encounters, underscoring the dynamic nature of Venus' magnetotail. Key observations include identifying boundary crossings such as the bow shock, observed down to approximately 60 Venus radii (6052 km) downstream, and the induced magnetospheric boundary roughly at 100 Venus radii downstream. This insight sheds light on the extent of the induced magnetosphere and allows for the refinement of existing boundary models. Previous models, based on data from Venus Express, were limited to within approximately five Venus radii of the planet; our analysis suggests modifications to better accommodate far-downstream encounters. Additionally, our analysis reveals the influence of solar wind conditions on magnetotail behavior: during Solar Orbiter's third encounter, characterized by extreme solar wind conditions, significant fluctuations in magnetosheath plasma density and magnetic field properties were observed. However, contrary to expectations perhaps, the increased dynamic pressure did not compress the magnetotail; instead, increased EUV flux during this period is suggested to have led to its expansion.
How to cite: Edberg, N. and the SolO, PSP and BepiC team: Far tail plasma boundaries at Venus from the Solar Orbiter, Parker Solar Probe and BepiColombo flybys, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-454, https://doi.org/10.5194/epsc2024-454, 2024.
Induced magnetospheres of non-magnetized atmospheric planets, like Mars and Venus, are formed by the ionospheric currents induced by the solar wind interaction with the gravitationally bound electrically conducting ionospheres. When the interplanetary magnetic field (IMF) is predominantly aligned to the solar wind velocity, the convective electric field diminishes, leading to a degeneration of the induced magnetosphere. We investigate a 4° cone angle case (angle between the solar wind velocity and the IMF) using observations from Mars Atmosphere and Volatile Evolution (MAVEN) and Mars Express (MEX), and a hybrid model of the solar wind interaction with Mars. The measurements and simulations are in agreement, allowing us to characterize the general structure of a degenerate induced magnetosphere. We find that no magnetic barrier is built. The am bipolar field defines the electrodynamics on the dayside and drives ionospheric ions up stream, forming a cloud of planetary ions. Solar wind protons propagates down to low altitudes and are lost through collisions with the neutral atmosphere, the respective magnetic field tubes deplete and a proton void form behind the planet. No bow shock is formed in the subsolar region, but shock-like structure form at the flanks. The most remarkable feature is a large cross-flow plume of planetary ions with a significant asymmetry, extending more than 10 Martian radii, driven by the ExB drift. The degenerate induced magnetospheres represent a distinctive mode in the solar wind interaction with non-magnetized planets and provide insight into the exoplanet-stellar wind interaction.
How to cite: Barabash, S., Zhang, Q., Holmström, M., Wang, X., Futaana, Y., Fowler, C., Ramstad, R., and Nilsson, H.: Degenerate induced magnetospheres: a distinctive mode of the solar wind interaction with non-magnetized bodies, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-276, https://doi.org/10.5194/epsc2024-276, 2024.
Fig. 1: Topside ionospheres of Venus and Mars as seen by (a) VEX VeRa, (b) MEX MaRS and (c) MAVEN ROSE.radio science.
While the orbital and environmental parameters of Venus and Mars show significant differences, their planetary ionospheres show notable similarities (Figure 1). The photochemically dominated regions of the undisturbed dayside ionospheres of Venus and Mars are both characterized by two major features. The ionospheric main peak region (V2 at Venus, M2 at Mars) is a result from photoionization by solar EUV irradiation. The weaker secondary V1/M1 region originates from the primary and secondary ionization of the neutral atmosphere caused by solar X-ray radiation. The upper region of the Venus and Mars dayside ionospheres is governed by transport processes.
The extent and shape of the ionospheric topsides is observed with the radio science experiments Venus Express Radio Science (VeRa) onboard Venus Express (VEX) [1] at Venus and Mars Express Radio Science (MaRS) [2] onboard Mars Express (MEX) and the Radio Occultation Science Experiment (ROSE) onboard the MAVEN spacecraft [3] at Mars. The observed electron density exhibits substantial variability on temporal scales and ranges from an undisturbed exponential decay (Fig. 1b) to strongly compressed shapes (Fig. 1a, c).
This work combines 9 years of VEX-VeRa (2006-2014), 18 years of MEX-MaRS (2004-2021) and 8 years of MAVEN-ROSE (2014-2021) radio occultation observations to investigate the variability of the topside ionospheres of Venus and Mars on the planetary dayside. The derived ionospheric characteristics will be compared to accompanying observations of the solar wind dynamic pressure (from VEX-ASPERA4 [4], MEX-ASPERA3 [5, 6] and MAVEN instruments [7]), solar irradiation flux (FISM-V2 model [8], MAVEN EUV monitor [9]) and a model of the crustal magnetic field for Mars [10] to improve our understanding of the solar wind interaction of planets without a global magnetic field.
References
[1] Häusler et al. (2006) PSS 54 (13-14)
[2] Pätzold et al. (2004) in Fletcher (2004) Mars Express. The scientific payload. ESA
[3] Withers et al. (2018) JGR Space Phys. 123 (5)
[4] Barabash et al. (2007) PSS 55 (12)
[5] Barabash et al. (2006) SSR 126
[6] Ramstad et al. (2015) JGR Planets 120 (7)
[7] Halekas et al. (2015) SSR 195
[8] Chamberlin et al. (2020) Space Weather 18 (12)
[9] Thiemann et al. (2017) JGR Space Physics 122 (3)
[10] Morschhauser et al. (2014) JGR Planets 119 (6)
How to cite: Peter, K., Pätzold, M., Withers, P., Ramstad, R., Thiemann, E., Fränz, M., Häusler, B., Futaana, Y., and Holmström, M.: Dynamics of the topside ionospheres of Venus and Mars as seen by recent radio science observations, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-481, https://doi.org/10.5194/epsc2024-481, 2024.
At planets with no intrinsic dipolar magnetic field such as Mars, an ionopause is often formed, a boundary that separates the planetary plasma from the solar wind. The ionopause boundary and its formation drivers in the upper dayside ionosphere of Mars are yet to be fully characterised. In this study, we use observations from NASA's MAVEN mission to probe the Martian upper dayside ionosphere and describe the physics of the ionopause boundary as well as its variability drivers. We develop an automated method to identify the ionopause as the location of sharp gradients in electron density and temperature. We focus on the 8th MAVEN deep dip campaign (DD8) from October 2017 that consists of 50 consecutive orbits. The trajectories of the DD8 orbits are similar to each other and thus, the impact of the changing upstream conditions on the Martian ionosphere can be studied. We utilise and compare data from several instruments on board MAVEN, namely the LPW, SWEA, STATIC, SWIA and MAG instruments, in order to investigate in detail the factors controlling the ionopause. We find that the ionopause formation is correlated with the plasma pressure balance between the ionosphere and the magnetosheath, and with changes in magnetic topology. More specifically, an ionopause in most cases is formed where there is a change from closed to either open or draped magnetic field lines.
How to cite: Stergiopoulou, K., Sánchez-Cano, B., Lester, M., M. Fowler, C., J. Andrews, D., Xu, S., J. T. Edberg, N., Joyce, S., Holmström, M., Meggi, D., K. Turner, A., and R. Gruesbeck, J.: The role of magnetic topology and plasma pressure on the ionopause formation at Mars, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-470, https://doi.org/10.5194/epsc2024-470, 2024.
It is commonly believed that because of the direct solar wind interaction with the Martian atmosphere/ionosphere, the planet could have lost a significant part of its atmosphere. Closed field lines of the crustal magnetic field can weaken a transport of the ionospheric ions to the tail. Reconnection of the interplanetary magnetic field lines draping around Mars and the crustal magnetic field can also lead to a presense of sunward fluxes of planetary ions that might affect the total ion loss. The LatHyS (LATMOS Hybrid Simulation) three-dimensional multispecies hybrid model is used here to characterize sunward fluxes of O+ and O2+ions and the magnetic field topology at Mars. It is shown that although reconnection between the interplanetary magnetic field (IMF) and the crustal magnetic fields strongly modifies the field topology, then sunward ion fluxes are rather small and do not significantly change the total ion loss. The results are compared with the MAVEN data.
How to cite: Dubinin, E., Modolo, R., Fraenz, M., and Paetzold, M.: Sunward oxygen ion fluxes and the magnetic field topology at Mars from hybrid simulations and observations, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-262, https://doi.org/10.5194/epsc2024-262, 2024.
After multiple Martian years and almost one full solar cycle in orbit, measurements from the MAVEN mission can now allow us to study the ionosphere. The statistical structure of the Martian ionosphere is assessed and presented here as a step towards a new empirical Martian Ionospheric Model for electron density and temperature. The ionosphere is assessed based on the most likely density and temperature and the variability of these numbers determined by many different conditions. The data will be presented as function of season, altitude, neutral pressure, solar location, and aerographic latitude. The influence of solar activity through solar irradiation and solar wind conditions are also considered. Furthermore, the data is examined based on local magnetic field strength, light versus heavy ionosphere composition, and the uniformity of the ionosphere. This work will identify effective approaches to characterizing the Martian ionosphere and thereby identify when and where different drivers influence its structure.
How to cite: Andersson, L., Pilinski, M., Bark, D., Shaver, S., Hesse, T., Shuvalov, S., and Andrews, D.: The Structure of the Martian Ionosphere, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-710, https://doi.org/10.5194/epsc2024-710, 2024.
Introduction
Mars’ lack of a global magnetic field led to low expectations for auroral phenomena on the planet, but MAVEN observations showed auroral activity to be frequent, diverse in nature, and often global in scope. Subsequent observations by the Emirates Mars Mission [1] further expanded the breadth of observable types of aurora, and it is likely that the variety will increase further as observations expand. Figure 1 below shows three fundamentally different types of aurora on Mars. Ironically, Mars’ lack of a global field is actually responsible for most of the activity, which leads to a new perspective for non-magnetized objects in our solar system and beyond.
Making Sense of Diverse Auroral Activity
Each of type of Mars aurora is a tracer for a different important process involving the interaction between solar influences and the near-Mars magnetic and charged particle environment. Originally, types of aurora were named for their resemblance to terrestrial or other types, with later forms named after their morphology, geographical location, precipitating particles, etc. The nomenclature became cumbersome, confusing, and not insightful to those not working in the field. At the same time, modeling showed that all types could fit into three categories based on the precipitating particles and their origins: solar energetic particles (SEPs), suprathermal electrons, and solar wind protons (see Figure 1). These distinctions usefully group the phenomena into clusters of phenomena observed and modelled similarly, and also allow for new varieties to be added.
Figure 1. Three types of aurora on Mars, as observed by the Imaging UltraViolet Spectrograph (IUVS) on MAVEN (left and right images) and the Emirates Ultraviolet Spectrometer (EMUS) on the Emirates Mars Mission (center image). Each is diagnostic of a specific interaction between solar or internal influences and Mars’ magnetic and plasma environment.
SEP Aurora on the Rise to Solar Max
This presentation will focus on SEP aurora, the type of aurora most dependent on solar activity. MAVEN/IUVS discovered that the entire visible nightside of Mars can be engulfed in auroral emissions [Figure 1, left, and reference 2]. The phenomenon can also be studied in limb scan mode, which revealed that
solar energetic particles can penetrate down to ~60 km altitude. Contemporaneous MAVEN/SEP observations of electrons up to 200 keV confirmed the correlation with solar activity. Some diffuse aurora events have been observed to last for days during extended solar events. Both SEP protons and electrons can be responsible [3].
SEP aurora events are currently occurring at the highest frequency of MAVEN’s 10 year mission. The phenomenon was discovered in 2014 during the declining phase of the solar cycle, and only two additional major events occurred in the following 7 years. Since August 2022, IUVS has observed 8 major events, half of which have occurred since February 2024 (Figure 2). (Additional SEP activity did occur throughout this period, but observations at those other times were not possible.) All auroral events are closely correlated with the arrival of SEP particles as measured by MAVEN’s SEP instrument.
Figure 2. MAVEN/IUVS image of SEP aurora (also known as diffuse aurora) on 18 March 2024 during a space weather event. Both the bright limb and on-disk emission are attributed to auroral emission. The near-UV image of Mars’ south polar region in southern spring was obtained contemporaneously with the auroral portion of the image by alternating detector gain during nadir scanning.
The substantial dataset of recent events will be ideal for comparative studies to determine (1) whether protons or electrons are responsible, and which energy ranges matter most; (2) how Mars’ hybrid magnetosphere responds to the SEP flux, and whether the auroral brightness is modulated by local structures or crustal magnetic fields.
In additional to auroral science goals, our efforts aim to quantify how aurora can serve as a proxy for space weather hazard for human exploration of Mars. This leads to the ironic situation where the aurora may be so impressive it’s necessary to seek shelter against the radiation.
Reaching Solar Max does not imply that auroral activity will soon decrease. In fact, the type of solar activity giving rise to SEP events may increase in the declining phase, with more burst of SEP aurora. MAVEN’s potential mission extension will be able to test this hypothesis.
The Case for Visible Nightside Imaging from Orbit.
Visible wavelength emissions are predicted to accompany UV emissions from SEP aurora, based on atomic and molecular physics with known branching ratios [4]. Oxygen green line emission is expected at 557 nm, as frequently seen at Earth. Brightnesses are expected to be detectable with visible wavelength cameras capable of long exposures. No orbital instruments on existing spacecraft have yet made detections, probably due to sensitivity limits in short exposures.
Future Mars missions with instruments designed for nightside imaging offer tremendous low-cost potential for breakthrough observations in auroral science. Visible filter imaging of the aurora with conventional technology is likely to be orders of magnitude more sensitive than the complex and expensive slit-scanning spectral imagers in orbit at Mars today. In addition to the [OI] green line emission, SEP aurora should also cause emission near the blue end of the visible range, emanating from the FDB bands of CO2+. The recent discovery of visible-wavelength nightglow [5] offers another compelling target for nightside imaging. The M-MATISSE mission, currently in a competitive Phase A Study for an ESA M-class mission, carries such a camera [6] . Even if selected, missions beyond should also carry low-cost visible imagers optimized for the orbit, observational capabilities and science goals of the mission.
References: [1] Lillis et al. (2022), GRL, doi: 10.1029/2022GL099820; [2] Schneider, et al. (2018). GRL, doi: 10.1029/ 2018GL077772. [3] Nakamura et al. (2020), JGR, doi: 10.1029/2021JA029914; [4] Gérard et al., (2015) JGR. 120, 6749–6765 doi: 10.1002/ 2015JA021150; [5] Gerard et al., Nat. Astr., 10.1038/s41550-023-02104-8; [6] Sanchez-Cano et al. (2023): doi 10.3389/fspas.2022.1101945
How to cite: Schneider, N., Jain, S., Cessna, J., Connour, K., Deighan, J., Jolitz, R., Lee, C., Larson, D., Rahmati, A., and Curry, S.: Mars Aurora on the Rise to Solar Max, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-581, https://doi.org/10.5194/epsc2024-581, 2024.
Mars is typically regarded as a non-magnetic planet. Currents in the Martian ionosphere generate a Venus-like induced magnetosphere to standoff the solar wind flows and to pile up the interplanetary magnetic fields. However, crustal magnetic fields in the southern hemisphere influence local plasma properties. Whether the crustal magnetosphere could be sustained is highly debatable and still uncertain. This work aims to provide evidence of a local crustal ’mini-magnetosphere’ in satellite observations on the Martian dayside, includes Mars Express, MAVEN, and Tianwen-1. The trapping effect causes different flow patterns while the crustal fields rotate to different sub-solar regions but are attenuated at higher altitudes. Observations provide essential information to investigate the effect of the crustal magnetic fields on heavy ion flows and understand the role of the crustal magnetic fields in the interaction between the solar wind and the Martian atmosphere.
How to cite: Fan, K., Fraenz, M., Wei, Y., Cui, J., Pan, Y., Yan, L., Wang, Y., Chen, S., and Dubinin, E.: Crustal magnetic fields' effect on the day-night transportation process in the Martian ionosphere, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-285, https://doi.org/10.5194/epsc2024-285, 2024.
| For the past few decades, it has demonstrated that gravity waves (GWs) and neutral winds can drive ionospheric irregularities on Earth. Still, as far as we know, the formation of ionospheric irregularity on Mars due to GWs has not been well studied. In this study, we use data from NASA's Mars Atmosphere and Volatile Evolution (MAVEN) mission to show evidence of an irregularity event in the Martian ionosphere, which is potentially seeded by the break of GWs (GWB). The statistical findings indicate that the observed ratio of GWB-related irregularity events varies from ~0.25 to 0.57 in each year, and the overall correlation for 2015 to 2020 is ~0.37. Numerical simulations provide further insight into the processes behind irregularities formation, which employs neutral wind shear as a source of perturbation in the context of the GWB. The simulations yield results fundamentally aligned with the observed characteristics of ionospheric irregularities observed in the 2018 event by considering the wind shear as the disturbance source. This study provides supplementary insights into the perturbation sources involved in shaping irregularities within the Martian ionosphere and presents valuable information about the coupling between the Martian ionosphere and the lower atmosphere. |
How to cite: Tian, R., Jiang, C., and Sánchez‐Cano, B.: Gravity Wave-Induced Ionospheric Irregularities in the Martian Atmosphere, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-34, https://doi.org/10.5194/epsc2024-34, 2024.
In the absence of solar radiation, precipitating electrons from the solar wind (SW) are generally thought to be the dominant source of energy deposition in the nightside Martian upper atmosphere, creating a patchy ionosphere and possibly also affecting the nightside thermal budget of various neutral and ionized species. Previous model calculations have not taken into account in situ heating via SW electron impact. In the present study, we utilize extensive measurements made by several instruments on board the Mars Atmosphere and Volatile Evolution spacecraft, in order to perform data-driven computations of the nightside neutral, ion, and electron heating rates. Considering the large range of energetic electron intensity observed on the nightside of Mars, we divide the entire data set into two subsamples, either with or without energetic electron depletion, a notable feature of the nightside Martian ionosphere. Our calculations indicate that in situ nightside neutral heating is dominated by exothermic chemistry and Maxwell interaction with thermal ions for regions with depletion, and by direct SW impact for regions without. Collisional quenching of excited state species produced from a variety of channels, such as electron impact excitation, dissociation, and ionization, as well as O2+ dissociative recombination, makes a substantial contribution to neutral heating, except during depletion. For comparison, nightside ion heating is mainly driven by energetic ion production under all circumstances, which occurs mainly via ion-neutral reaction O+ + CO2 and CO2+ predissociation.
How to cite: Niu, D. and Cui, J.: In Situ Heating of the Nightside Martian Upper Atmosphere and Ionosphere: The Role of Solar Wind Electron Precipitation, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-295, https://doi.org/10.5194/epsc2024-295, 2024.
We present observations of a low-altitude nightside ionisation layer in the Martian ionosphere during a period of Solar Energetic Particle induced radar blackout. The interval, in December 2014, has an unprecedented coverage of data from the MARSIS Advanced Ionospheric Sounder (AIS) onboard Mars Express. The orbit of Mars Express is ideal during this interval as it has periapsis close to the terminator and spends much of the AIS observational period on the nightside, where the layer is observed to form. During the SEP period, the surface return signal is lost as a result of absorption of the radar signal along its path to and from the surface. This absorption appears to have been caused by a low-altitude layer of ionisation created by the SEP event. The AIS observed an ionospheric trace, unusual for the nightside, which we interpret as evidence for the low-altitude layer. We demonstrate the variation of the peak electron density of this layer as a function of time and the SEP electron and ion energy flux. We conclude that although the ions may have played a role in the creation of this layer, the electrons are most likely the major cause.
How to cite: Lester, M., Sanchez-Cano, B., Joyce, S., Meggi, D., Stergiopolou, K., Opgenoorth, H., Lillis, R., Witasse, O., Orosei, R., Cartacci, M., and Harada, Y.: Radar Blackouts at Mars and Solar Energetic Particles: The Low Altitude Ionisation Layer, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-1023, https://doi.org/10.5194/epsc2024-1023, 2024.
A climatological survey of Martian ionospheric plasma density irregularities was conducted by exploring the in-situ measurements of the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. The irregularities were first classified as enhancement, depletion, and oscillation. By checking the simultaneous magnetic field fluctuation, the irregularities have been classified into two types: with or without magnetic signatures. The classified irregularities exhibit diverse global occurrence patterns, as those with magnetic signatures tend to appear near the periphery of the crustal magnetic anomaly (MA), and those without magnetic signatures prefer to appear either inside of the MA or outside of the MA, depending on the type and solar zenith angle. Under most circumstances, the irregularities have a considerable occurrence rate at altitudes above the ionospheric dynamo height (above 200 km), and the magnetization state of the ions seems irrelevant to their occurrence. In addition, the irregularities do not show dependence on magnetic field geometry, except that the enhancement without magnetic signatures favors the vertical field line, implying its equivalence to the localized bulge (Duru et al., 2006). Other similarities and discrepancies exist in reference to previous studies. We believe this global survey complements previous research and provides crucial research clues for future efforts to clarify the nature of the Martian ionospheric irregularities.
How to cite: Wan, X., Zhong, J., Xiong, C., and Cui, J.: Preliminary Results of the Categorizing and Statistical Survey of Martian Ionospheric Irregularities, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-1287, https://doi.org/10.5194/epsc2024-1287, 2024.
Comet 67P/Churyumov-Gerasimenko was escorted by the Rosetta spacecraft through a 2 year section of its 6 year orbit around the Sun. This enabled the observation of a large variation in comet outgassing and the resulting evolution of the plasma environment. The diamagnetic cavity, a region of negligible magnetic field arising from the interaction of the unmagnetised cometary plasma with the solar wind, began to be detected sporadically by the Rosetta Plasma Consortium/ Magnetometer (RPC/MAG) in April 2015 at a heliocentric distance of 1.8 au [1]. The last detections were in February 2016 at 2.4 au. Within this cavity, the flow of cometary ions has been shown to be largely radial [2]; the ions are accelerated above the neutral gas speed by an ambipolar electric field, but many newborn ions still undergo multiple ion-neutral chemical reactions before escaping [3,4]. Outside the diamagnetic cavity boundary, which is itself highly variable, the ion flow is considerably more complex, and the ambipolar electric field plays a more minor role compared to the convective electric field of the solar wind [2]. At large heliocentric distances (>2.5 au), the total plasma density observed from RPC plasma sensors is well explained by a simple flux conservation model that assumes the ions travel radially away from the nucleus at speed close to that of neutrals [5,6]. However, closer to perihelion and once the diamagnetic cavity has formed, such an approach does not hold [7]. We aim to better understand this transition, the driver of ions' acceleration, and the role that the diamagnetic cavity plays.In this study, we explore the varying ion dynamics both in the presence (e.g. during high outgassing activity) and absence (low outgassing activity) of a diamagnetic cavity. Electric and magnetic fields from hybrid simulations of the cometary environment are used to drive a 3D test particle model of the cometary ions for a range of comet activity levels. We model the behaviour of three key ion species, H2O+, H3O+, and NH4+, in order to assess the impact of the ion dynamics on the ionospheric composition and density.
[1] Goetz et al. MNRAS S 462, S459–S467 (2016)
[2] Koenders et al., Planetary and Space Science, 101-116, 105 (2015)
[3] Lewis et al., MNRAS, 523, 6208–6219 (2023)
[4] Lewis et al 2024, MNRAS, 530, 66–81 (2024)
[5] Galand et al., MNRAS, S331-S351, 462 (2016)
[6] Heritier et al., A&A, 618 (2018)
[7] Vigren et al., ApJ 6, 881(1) (2019)
How to cite: Lewis, Z., Stephenson, P., Kallio, E., Galand, M., and Beth, A.: Evolution of the ion dynamics at comet 67P during the escort phase, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-219, https://doi.org/10.5194/epsc2024-219, 2024.
