The solar wind is slowed, deflected, and heated as it encounters Venus's induced magnetosphere. The importance of kinetic plasma processes to these interactions has not been examined in detail, due to a lack of constraining observations. In this study, kinetic-scale electric field structures are identified in the Venusian magnetosheath, including plasma double layers. The double layers may be driven by currents or mixing of inhomogeneous plasmas near the edge of the magnetosheath. Estimated double layer spatial scales are consistent with those reported at Earth. Estimated potential drops are similar to electron temperature gradients across the bow shock. Many double layers are found in few high cadence data captures, suggesting that their amplitudes are high relative to other magnetosheath plasma waves. These are the first direct observations of plasma double layers beyond near-Earth space, supporting the idea that kinetic plasma processes are active in many space plasma environments.

We present general empirical analytical equations of bow shock structures historically used at Mars, and show how to estimate automatically the statistical position of the bow shock with respect to spacecraft data from 2D polar and 3D quadratic fits. Analytical expressions of bow shock normal in 2D and 3D are given for any point on the shock’s surface. This empirical technique is applicable to any planetary environment with a defined shock structure. Applied to the Martian environment and the NASA/MAVEN mission, the predicted bow shock location from ephemerides data is on average within 0.15 planetary radius Rp of the actual shock crossing as seen from magnetometer data. Using a simple predictor-corrector algorithm based on the absolute median deviation of the total magnetic field and the general form of quasi-perpendicular shock structures, this estimate is further refined to within a few minutes of the true crossing (≈0.05 Rp). With the refined algorithm, 14,929 bow shock crossings, predominantly quasi-perpendicular, are detected between 2014 and 2021. Analytical 2D conic and 3D quadratic surface fits, as well as standoff distances, are successively given for Martian years 32 to 35, for several (seasonal) solar longitude ranges and for two solar EUV flux levels. Although asymmetry in Y and Z Mars Solar Orbital coordinates is on average small, it is shown that for Mars years 32 and 35, Ls = [135-225] degrees and high solar flux, it can become particularly noticeable and is superimposed to the usual North-South asymmetry due to the presence of crustal magnetic fields.

We describe a new method to analyze the properties of plasma waves, and apply it to observations made upstream from Mars by the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. The slow measurement cadence of most charged particle instrumentation has limited the application of analysis techniques based on correlations between particle and magnetic field measurements. We show that we can extend the frequency range of applicability for these techniques, for a subset of waves that remain coherent over multiple wave periods, by sub-sampling velocity distribution function measurements and binning them by the wave phase. This technique enables the computation of correlations and transport ratios for plasma waves previously inaccessible to this technique at Mars. By computing the cross helicity, we find that most identified waves propagate upstream in the plasma frame. This supports the conclusions of previous studies, but enables a clearer determination of the intrinsic wave mode and characteristics. The intrinsic properties of observed waves with frequencies close to the proton cyclotron frequency have little spatial variability, but do have large temporal variations, likely due to seasonal changes in the hydrogen exosphere. In contrast, the predominant characteristics of waves at higher frequencies have less temporal variability, but more spatial variability. We find several indications of the presence of multiple wave modes in the lower frequency wave observations, with unusual wave properties observed for propagation parallel to the magnetic field and for background magnetic fields nearly perpendicular to the solar wind flow.

The canonical picture of the magnetotail of unmagnetized planets consists of draped interplanetary magnetic fields (IMF) forming opposite-directed lobes, separated by the current sheet. \citet{DiBraccio2018twisted} showed that Mars’ magnetotail has a twist departing from this picture. Magnetohydrodynamic (MHD) results suggest that open field lines connected to the planet that populate portions of the tail cause the apparent twist. To validate this interpretation, we compare the tail topology determined from MHD simulations to that inferred from data collected by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, in particular how each topology responds to the upstream IMF orientation. The occurrence rates for open topology from both data and MHD varies with IMF polarities in a similar fashion as the tail twisting. This suggests that Mars’ crustal fields have a global effect on the magnetosphere configuration, supporting the picture of a “hybrid” magnetotail that is partly induced/draped and partly intrinsic/planetary in origin.

The study of lunar plasma environment’s response to the extreme solar wind condition is the main subject of our investigation in this report. The computational model includes the self-consistent dynamics of the light (H_2+) and (He+), and heavy (Na^+}) pickup ions. The electrons are considered as a fluid. The lunar interior is considered as a weakly conducting body. The input parameters are taken from the ARTEMIS observations. The modeling demonstrates a formation of the various plasma structures near the Moon: (a) bow shock wave with split shock transition in case of extreme solar wind density and standard bulk velocity; (b) hyper-sonic/Alfvenic Mach cone in case of extreme solar wind bulk velocity and moderate solar wind density. The modeling shows a strong asymmetry in the solar wind ion VDF which connected with a plasma compression and ion reflection at the bow shock wave/Mach cone front.

At Mars, charge exchange between solar wind protons and neutral exospheric hydrogen produces energetic neutral atoms (ENAs) that can penetrate into the collisional atmosphere, where they can be converted through collisions into H+ and H–. The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission observed a population of negatively charged particles at low altitudes, whose energies, angular distribution, and dependence on the upstream solar wind were consistent with H–originating in the solar wind. The highest fluxes of H– were observed near perihelion and the southern summer solstice. We calculated an average ratio of ~4% between H– density and H+ density, implying a slightly smaller relative abundance than reported previously (~10%). We found that the fraction of H ENAs converted to H– increases with the solar wind energy, in agreement with laboratory measurements of the H–CO2 electron capture cross section.

The Mars Atmosphere and Volatile EvolutionN (MAVEN) spacecraft can act as an intermittent upstream solar wind monitor at ~ 1.5 AU. To inspect the evolution of solar wind turbulence in the Martian exosphere, we have gathered proton (i.e., ionized hydrogen) temperature measurements taken by the Solar Wind Ion Analyzer (SWIA) onboard the MAVEN spacecraft. Here we investigate instabilities driven by the proton temperature anisotropy at Mars. We look at the temperature anisotropy T⊥p/T||p (i.e., the ratio of the perpendicular proton temperature component to the parallel proton temperature component) and the parallel plasma beta, β||p, to determine the active plasma instability mode. Furthermore, we report on the properties of turbulence near Mars’ orbital location during upstream solar wind intervals from January 2015 to December 2016 (~ 1 Martian year). We find that the probability distributions of (β||p, Rp)-values are limited at Rp >1 and Rp <1. We also find evidence of intermittency implying nonlinear, non-homogeneous energy transfer. Additionally, spectral index values near the Kolmogorov scaling value are observed for the inertial range (10-4 Hz to 0.1 Hz).

Above lunar crustal magnetic anomalies, large fractions of solar wind electrons and ions can be reflected and stream back towards the solar wind flow, leading to a number of interesting effects such as electrostatic instabilities and waves. These electrostatic structures can also interact with the background plasma, resulting in electron heating and scattering. We study the electrostatic waves and electron heating observed over the lunar magnetic anomalies by analyzing data from the Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon’s Interaction with the Sun (ARTEMIS) spacecraft. Based on the analysis of two lunar flyby events in 2011 and 2013, we find that the electron two-stream instability (ETSI) and electron cyclotron drift instability (ECDI) may play an important role in driving the electrostatic waves. We also find that ECDI, along with the modified two-stream instability (MTSI), may provide the mechanisms responsible for substantial isotropic electron heating over the lunar magnetic anomalies.

In planetary bow shocks, binary particle collisions cannot mediate the conversion of upstream bulk flow energy into downstream thermal energy, and wave-particle interactions in part assume this role. Understanding the contribution of waves to shock heating requires knowledge of the modes that propagate in different classes of shocks; we describe the growth patterns of whistler waves within the Venusian bow shock. Waves with frequencies $f \lesssim 0.1 f_{ce}$, where $f_{ce}$ is the electron cyclotron frequency, preferentially grow at local minima in the background magnetic field $|B_0|$. Quasi-parallel propagating whistlers with frequencies between $0.1 f_{ce}$ and $0.3 f_{ce}$ are strongest at the downstream ramps of these $|B_0|$ minima. Immediately downstream of the shock, whistlers with frequencies $f < 0.1 f_{ce}$ propagate more than 80$^\circ{}$ oblique from $\vec{B}_0$ and have elliptically polarized $\vec{B}$ fields. A prediction from kinetic theory of the orientation of these waves’ $\vec{B}$ ellipses is confirmed to high accuracy.

Crustal magnetic fields influence a range of plasma processes at Mars, guiding the flow of energy from the solar wind into the planet’s atmosphere at some locations while shielding it at others. In this study we investigate how these crustal fields vary with changes in the direction of the incoming interplanetary magnetic field (IMF). Using spacecraft measurements of electron flux and magnetic field, we analyze magnetic topology throughout the Martian ionosphere for different IMF configurations. We find that the topology of crustal field cusp regions is dependent on IMF direction, and that cusps transition between open and closed topology regularly as they rotate through the nightside of Mars. Finally, we determine that cusps often become topologically closed due to reconnection with open magnetic fields in the Martian magnetotail, resulting in large day-to-night closed loops that could represent a source of energy input into nightside crustal field regions.

The Solar Probe ANalyzer for Ions (SPAN-I) onboard NASA’s Parker Solar Probe (PSP) spacecraft is an electrostatic analyzer with time-of-flight capabilities that measures the ion composition and three dimensional distribution function of the thermal corona and solar wind plasma. SPAN-I measures the energy per charge of ions in the solar wind from 2 eV to 30 keV with a field-of-view of 247.5 • x 120 • while simultaneously separating H + from He ++ to develop 3D distribution functions of individual ion species. These observations, combined with reduced distribution functions measured by the Sun-pointed Solar Probe Cup (SPC), will help us further our understanding of the solar wind acceleration and formation, the heating of the corona, and the acceleration of particles in the inner heliosphere. This paper describes the instrument hardware, including several innovative improvements over previous time-of-flight (TOF) sensors, the data products generated by the experiment, and the ground calibrations of the sensor.

Depressions in magnetic field strength, commonly referred to as magnetic holes, are observed ubiquitously in space plasmas. Sub-proton-scale magnetic holes with spatial scales smaller than or on the order of $\rho_p$, are likely supported by electron currents vortices, rotating perpendicular to the ambient magnetic field. While there are numerous accounts of sub-proton-scale magnetic holes within the Earth’s magnetosphere, there are no reported observations in other space plasma environments. We present the first evidence of sub-proton-scale magnetic holes in the Venusian magnetosheath. During Parker Solar Probe’s first Venus Gravity Assist, the spacecraft crossed the planet’s bow shock and subsequently observed the Venusian magnetosheath. The FIELDS instrument suite onboard the spacecraft achieved magnetic and electric field measurements of magnetic hole structures. The electric field associated with magnetic depressions are consistent with electron current vortices with amplitudes on the order of 1 $\mu$A/m$^2$.