TP18
Session assets
Discussion on Slack
Orals: Wed, 21 Sep | Room Machado
Interaction of a spacecraft with ambient plasma results in charging of the spacecraft to a potential of the order of the electron temperature. This is an issue for the ion measurements in the low altitude Martian ionosphere, since the potential energy of the ions in the spacecraft’s electric field is comparable to their thermal energy. However, the unique Mars Express payload makes possible the use of an innovative technique to study this low energy ionospheric population around the spacecraft. It has been discovered that operating the radar MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) onboard Mars Express results in acceleration of the local thermal ions to energies up to 800 eV. Accelerated ions are readily detected by the ion detector of the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3). The analysis of these ASPERA-3 observations showed that that the voltage applied to the MARSIS antenna causes charging of the spacecraft to several hundreds of volts by the electrons of the ambient plasma. Individual observations of accelerated ions consist of almost mono-energetic ion beams that allow measuring densities of the main (O+, O2+ and CO2+) and even minor (O2++, C+, CO+) ionospheric thermal populations. This novel technique of active sounding opens new possibilities to study the Martian ionosphere.
From 2007 to 2016 2,528 Mar Express orbits were found to exhibit sounder accelerated ions (SAI). Created catalogue of the SAI events contains more than 50,000 SAI entries. This allowed to study the mechanisms that causes acceleration of thermal ions in the vicinity of an active transmitter in a plasma with no strong magnetic led. Based on it, a model was developed, that allows to estimate density of cold ionospheric ions from SAI observations.
Figure 1 shows an example of the ion density retrieved using the developed method. Top panels show the ion differential flux measured by IMA. Cold ionospheric plasma is visible as an intense signal at energy close to 10 eV. SAI are present as intense periodic disturbances within energy range between 30 and 800 eV. Bottom panels show comparison of the local electron density estimated using MARSIS ionograms and the ion density estimated from the SAI observations. As one can see, values are in a good agreement and follow similar dependence on altitude and SZA. Both methods show peak of the plasma density close to the periapsis.
Acceleration of the ionospheric plasma above thermal energy facilitates determination of the ion composition by IMA. Figure 2 shows altitude profiles for different ionospheric constituents measured using SAI by MEX. At the altitudes above 300 km main ionospheric species are O2+ and O+ . Corresponding densities decrease from 750 pp/cm3 at 300 km to 400pp/cm3 at 500 km. It is interesting to note that at the altitudes 300-350 km density of O+ is higher than the density of O2+ while on higher altitudes situation is opposite. Similar results were found by MAVEN.
Figure 2: Examples of altitude profiles of different ionospheric constituents obtained from the SAI observations.
Extensive database of the SAI covers more than one solar cycle enabling study of the variability of the Martian ionosphere. Figure 3 shows altitude profiles of the CO2+, O2+ and O+ for the periods of dierent EUV irradiance. For all of the species density increases with increase in EUV irradiance. However different species have dierent response to the increase in EUV irradiance. For the period with low EUV (left panel) density of O+ is higher than that of O2+ at the altitudes below 400 km. In the case of medium EUV flux (middle panel) the densities of these to species are almost equal. For the period of high EUV flux density of O2+ is higher.
SAI database can be used to study the impact of the Martian magnetic anomalies on the ionospheric densities. Figure 4 shows altitude density profiles for regions with closed and open magnetic field lines. Both profiles exhibit similar behavior: ion density decreases by 25% as altitude increases from 300 to 450 km. A notable difference is that the ion density above regions with open magnetic field line is much higher. This result is in agreement with the previous studies. In the open field regions, the ionosphere is more inflated than in other regions since it is easier here for plasma at lower altitudes to diffuse upward. In the regions with strong horizontal field situation is different. In these regions, horizontal drifts due to plasma pressure gradients move plasma particles toward the local magnetic equator where plasma gets trapped. The effects of this trapping on plasma density become more apparent above 170 km, where the effects of collisions between plasma and the neutral atmosphere become negligible compared with plasma transport processes. The vertical transport is inhibited by a horizontal magnetic field resulting in depletion of the ionosphere above these regions.
Figure 3: Altitude proles for O2+, O+ and CO2+ estimated from the SAI observations. Left panel: altitude profiles obtained for the period of the low EUV flux, middle panel - for the period of medium EUV flux, right panel - the period of high EUV flux.
Figure 4: Altitude profiles of the averaged ion density above the regions with strong magnetic field. Red line - modeled magnetic field angle is horizontal. Blue line - modeled magnetic field normal angle is radial.
Particle acceleration by sounders in the planetary ionospheres is a type of active experiments of great interest. These phenomena are a result of routine operation of satellite-borne sounders and do not require any additional spacecraft or mission resources, an important factor for planetary missions with scarce resources. Sounder accelerated ions detected on Mars Express enabled development of the method that allows to retrieve ion density and composition of cold ionospheric populations. This method was used to study the variability of the Martian ionosphere composition within solar cycle. In addition it was used to study of the crustal magnetic field on the ionospheric density.
How to cite: Voshchepynets, A., Barabash, S., Holmström, M., Titov, D., Orosei, R., Martin, P., and Sanchez-Cano, B.: Sounder accelerated ions: a new technique revealing new ionospheric properties as observed by Mars Express, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-700, https://doi.org/10.5194/epsc2022-700, 2022.
The localized crustal magnetic anomalies scattered across the surface Mars create a unique, hybrid magnetosphere. Over regions of strong crustal magnetism (100-1000 nT at the surface), the crustal anomalies protrude up to thousands of kilometers in space and a create a “mini-magnetospheric” interaction with the draped interplanetary magnetic field (IMF). One consequence of this interaction is the occurrence of discrete aurora on the nightside of Mars via electron precipitation and energy deposition into the planet’s atmosphere stimulating light emission (Bertaux et al., 2005). Discrete auroral emissions from electron impact with atmospheric CO2 in the mid ultra-violet have been observed via the Imaging Ultra-Violet Spectrograph (IUVS) instrument onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. These emissions have been preferentially observed over the region of strong crustal magnetism in the southern hemisphere (~153°-213° E longitude, 30°S-70°S latitude) and favor “open” magnetic field lines (i.e., one end connected to the IMF, the other connected to the planet) (Schneider et al., 2021). These trends suggest discrete aurora at Mars may form via magnetic reconnection between the strong crustal anomalies and the draped IMF around the planet. Magnetic reconnection is a process that can “open-up” the closed crustal magnetic fields at Mars and accelerate electrons along these magnetic field lines. However, there has yet to be a study that links these two phenomena directly, and as a result, our understanding of discrete auroral formation at Mars remains poorly understood.
In this study, we uncover the relationship between magnetic reconnection and discrete aurora at Mars by analyzing the draped magnetic field conditions during 78 discrete auroral emissions observed via nadir observations taken by the IUVS within the region of strong crustal fields. First, we simplify the crustal field region into its two primary constituents: one crustal anomaly that is positioned in the northern half of the region and closes northward, and one crustal anomaly that is positioned in the southern half of the region and closes southward (Figure 1). We note that the discrete auroral emissions tend to fall on the “footprints” of the two crustal anomalies where the dominant component of the crustal magnetic field points radially into or out of the planet. Two plasma regimes are more susceptible to reconnection when their magnetic field orientations are anti-parallel to one another. Therefore, we hypothesize that if crustal field-draped IMF magnetic reconnection plays a role in discrete auroral formation over the strong crustal anomalies at Mars, then a southward draped IMF would activate auroral emissions over the northern crustal anomaly and a northward draped IMF would activate auroral emissions over the southern crustal anomaly.
We estimate the orientation of the draped magnetic field over this region of strong crustal magnetism using data obtained from the magnetometer instrument onboard MAVEN along the same orbit in a discrete auroral emission was detected by IUVS. We find that the estimated orientation of the draped magnetic field associated with each discrete auroral event shows a regional dependence consistent with our hypothesis: discrete auroral emissions over the footprints of the northern anomaly are associated with southward draped fields, and emissions over the footprints of the southern anomaly are associated with northward draped fields (Figure 2). We also demonstrate that these findings hold implications for other trends reported in previous studies of discrete aurora over this region of crustal fields, namely a trend in local time and upstream IMF conditions. This study is the first to more definitively link magnetic reconnection to discrete aurora formation on the nightside of Mars.
Bertaux, J., F. Leblanc, O. Witasse, E. Quemerais, J. Lilensten, S. Stern, B. Sandel, and O. Korablev (2005), Discovery of an aurora on Mars, Nature, 435(7043), 790-794.
Schneider, N., et al. (2021), Discrete Aurora on Mars: Insights Into Their Distribution and Activity From MAVEN/IUVS Observations, Journal of Geophysical Research-Space Physics, 126(10).
How to cite: Bowers, C., Slavin, J., DiBraccio, G., Johnston, B., and Schneider, N.: Magnetic Reconnection and Discrete Aurora at Mars: MAVEN Observations, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-170, https://doi.org/10.5194/epsc2022-170, 2022.
Titan's ionosphere has a global presence of dusty (ion-ion) plasma a few hundreds of kilometers below the photoionization peak altitudes. Recent studies have shown that charged dust dramatically alters the electric properties of plasmas, in particular planetary ionospheres. Titan is immersed in magnetospheric plasma and magnetic field of Saturn (most of the time) and the moons ionospheric conductivities define the interaction with its environment.
We present revisited electric conductivities and the conductive dynamo region of Titan’s ionosphere using the full plasma content (electrons, ions+, and ions–/dust–) from 13 years of in-situ measurements by the Cassini mission. We show that the traditional approach of only using the easily detectable electron densities underestimates the Pedersen conductivities at ∼1,100–1,200 km altitude by up to 35%. The Hall conductivities are in general not affected but several cases indicate a reverse Hall effect at closest approach (∼900 km altitude) and below. We also identify a dayside-nightside asymmetry, with dayside conductivities a factor ∼7–9 larger than on the nightside (due to higher plasma densities).
Figure 1 shows the median profiles of the Pedersen, Hall and magnetic field parallel conductivities plotted in altitude and versus the neutral atmosphere, color-coded into dayside, terminator and nightside. First thing to note is that due to the extent of Titan’s atmosphere and ionosphere, plotting versus altitude results in noticeable less organized data due to atmospheric variations. These profiles scale with the plasma densities so their trends propagate – we identify solar cycle effects that match those on the heavy charge carriers.
Figure 1. Sliding median conductivity profiles: Pedersen (panels a1, b1), Hall (panels a2, b2) and Parallel (panels a3, b3). The total medians are in solid black. The colored lines are medians for the dayside (SZA<70), terminator (70≤SZA<100) and nightside (SZA≥100). Adapted from Shebanits et al. (2022).
The study is available in open access and includes the dataset: https://doi.org/10.1029/2021JA029910 .
How to cite: Shebanits, O., Wahlund, J.-E., Waite, H., and Dougherty, M.: Electric conductivities of Titan’s dusty ionosphere, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-799, https://doi.org/10.5194/epsc2022-799, 2022.
- 1Swedish Institute of Space Physics, Uppsala, Sweden
- 2KTH Royal Institute of Technology, Stockholm, Sweden
The ionospheres of comets are complex systems, where dynamic phenomena such as plasma instabilities and turbulence commonly occur as a consequence of the coupling processes between solar wind and cometary plasma. The analysis of fluctuations of plasma density, magnetic and electric fields observed by ESA’s Rosetta spacecraft during its 2-year mission to comet 67P/Churyumov-Gerasimenko suggest the existence of a turbulent state in the cometary plasma environment, which may be at the heart of important dynamical processes and have consequential impact on the cross-scale coupling.
Rosetta’s prolonged stay in the inner plasma environment of 67P provided the instruments of the Rosetta Plasma Consortium (RPC) with an unprecedented long-term view of the inner coma and plasma environment of an intermediately active comet. We use data from the Langmuir probe (RPC-LAP), magnetometer (RPC-MAG) and mutual impedance probe (RPC-MIP) to investigate the fluctuations and dynamics of plasma density, magnetic and electric fields across time-scales from ~10-1-103 s. Recurring density enhancements of several hundred percent occur on typical time scales of a few minutes, c.f. Figure 1a. Similar enhancements are also seen in the magnetic field magnitude, though not quite as large (δB/B~1), c.f. Figure 1b. Time-averaged wavelet spectra of both density and magnetic field from a 4-hour interval (including the example time series in Figure 1), c.f. Figure 2, exhibit clear maxima at a period of about 3 minutes, quantifying and confirming the importance of this characteristic time scale in the cometary plasma environement, at least for this time period.
The observed 3-min structures represent a source of energy, corresponding to a peak in the power spectral density and to the saturation scale of the second order structure function of the field fluctuations, c.f. Figures 3a and 4a. At shorter time scales, spectra show power law scaling with exponents close to 5/3, typical of Kolmogorov turbulence. A power-law scaling range is also observed between 3 min and ~1 s for the normalized fourth-order moment of the scale-dependent fluctuations, the "flatness", a standard indicator of intermittency in turbulence, shown in Figures 3b and 4b. The scaling exponent of the flatness is comparable with typical observations in the turbulent solar wind. Kolmogorov spectra and strong intermittency are a robust indication that the dynamics is dominated by nonlinear interactions, which induce a cross-scale transfer of energy, the so-called turbulent cascade, over a broad range of smaller scales. This turbulent cascade can heavily influence particle heating and acceleration at the comet, as well as the structure and dynamics of the plasma in the inner coma, and thus play an important role for shaping the cometary plasma environment.
How to cite: Odelstad, E., Sorriso-Valvo, L., Eriksson, A., and Karlsson, T.: Plasma turbulence at comet 67P, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1140, https://doi.org/10.5194/epsc2022-1140, 2022.
Posters: Thu, 22 Sep, 18:45–20:15 | Poster area Level 1
A suitable view of the distribution of the velocity vectors of the H+ solar wind ions measured with the VEX spacecraft projected on a plane transverse to the wake direction is reproduced in Figure 1 to describe a vortex shape configuration. The velocity distribution is oriented in a geometry different from what would be produced by magnetic tension forces along the field lines from the Venus polar regions. Instead, flow motion is dominant to produce the vortex shape in the particle displacement.
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.
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.
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.
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 (Ne). 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 6th to 13th of June 2011 and 16th February to 31st March 2015. Using the Level 2 data we calculated the Ne 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 8th 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.