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Ions originating from the upper atmosphere of Mars may be picked up by the impinging solar wind and interplanetary magnetic field (IMF), which forms an energetic ion plume from the dayside of the planet as a key feature of the Martian induced magnetosphere and an important ion escape channel. Consisting of mostly ions in the beginning phase of the pickup process, the orientation and morphology of the plume are largely controlled by upstream IMF conditions.Using data from the NASA Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, we will perform a thorough investigation of the pickup ion plume under different upstream IMF conditions. Previous statistical ion flux maps by Dong et al. [2015; 2017] from MAVEN data show the plume as a more spatially spread-out feature than that in many simulation models [e.g. Jarvinen et al. 2016 and others], which is possibly due the effects of highly variable IMF conditions for the data used in those maps. We will investigate how the plume appears with selected data under quasi-steady IMF conditions. Furthermore, we will compare the plume under strong and weak IMF conditions, as well as the conditions with IMF approximately perpendicular or parallel to the solar wind direction. The morphology of the plume and characteristics of escaping pickup ions under different IMF conditions will be discussed and compared with available model results to better understand how IMF affects the formation of the plume and ion escape through this channel.

Mars is an unmagnetized planet meaning that it has no internally generated global dipole magnetic field; the solar wind interaction with Mars is thus highly dependent on upstream conditions that include the orientation of the Interplanetary Magnetic Field (IMF). This interaction controls the transfer of energy and momentum from the solar wind into the magnetosphere, ionosphere and atmosphere, driving structure and dynamics within each. The Mars-solar wind interaction has been studied in detail for “nominal” Parker Spiral IMF conditions, but few studies exist that investigate the interaction under less typical “radial IMF” conditions. We utilize in-situ measurements made by NASAs Mars Atmosphere and Volatile EvolutioN (MAVEN) mission during radial IMF conditions at Mars to identify several prominent features that arise during this interaction:Highly disturbed magnetic and plasma conditions exist over the nose of the planet, which are reminiscent of foreshock like conditions and indicative of radial IMF. Solar wind protons and alphas are observed to penetrate directly into the dayside ionosphere down to MAVEN periapsis altitudes (~230 km). The magnetic pileup region (or magnetic barrier) forms deep within the dayside ionosphere, directly exposing significant heavy planetary ion densities above to the solar wind flow. Planetary ions above the magnetic barrier are mass loaded by the solar wind flow, characterized by signatures consistent with VxB acceleration under near radial IMF conditions. Thermal ion distributions in the ionosphere are observed to possess significant suprathermal energetic tails, suggesting that additional energization mechanisms are present that heat the cold ion core. Electron and ion temperatures are 2-10 times higher than average values that occur under more typical IMF conditions. Significant erosion of the dayside upper ionosphere occurs and appears to drive substantial ion escape to space.

Measurements of Energetic Neutral Atoms (ENAs) provide information about both the plasma and neutral components along the line-of-sight for any ENA instrument, though the individual influences of the plasma and neutral environments are convoluted due to the nature of the charge-exchange ENA generation process. We combine ion flux and magnetic field measurements from the Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiter at Mars with models for the Martian exospheric components to predict the average observable 10 eV – 10 keV oxygen and hydrogen ENA distributions from virtual orbits in the near-Mars space environment. The predicted distributions are consistent with past ENA measurements, informing and constraining future ENA investigations of the neutral and plasma near-Mars space environments.

Through phase-space mapping 6 yr of H+, O+, and O 2 + distributions measured in situ by the Mars Atmosphere and Volatiles EvolutioN (MAVEN) orbiter, we derive semiempirical average energetic neutral atom (ENA) distributions near Mars. Differential fluxes of H-ENAs and O-ENAs are estimated by line-integrating ENA production and loss rates in the average phase-space ion distributions. By repeating the procedure for a systematic series of vantage points, we produce synthetic ENA observations for virtual circular orbits with radii twice that of Mars, revealing the angular dependence of the observer’s position. Accounting for known ENA production and loss terms, we find that H+ in the upstream solar wind yields total antisunward H-ENA fluxes of ∼3 × 105 cm−2 s−1. The dayside magnetosheath produces H-ENA angular-differential fluxes of up to 3 × 105 cm−2 s−1 sr−1, while the magnetosheath flanks populate the planet’s nightside with H-ENA fluxes in the range of 104–105 cm−2 s−1 sr−1. The O-ENA environment is dominated by a near-isotropic ∼105 cm−2 s−1 sr−1 relatively low-energy (tens of eV) population originating in the top-side ionosphere, particularly on the dayside. Lower fluxes (103–104 cm−2 s−1 sr−1) of energetic O-ENAs (≳100 eV) are mainly found on the nightside and above the electric polar regions of the induced magnetosphere. Asymmetries in the ENA flow are largely limited to the energetic O-ENA populations, while the H-ENA distribution is mostly symmetric around the Sun‒Mars line. We discuss how synthetic ENA observations can provide insight into the near-Mars space environment, including the planet’s plasma environment and exosphere.