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The Solar Energetic Particle (SEP) Instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft is meant to characterize the variability of SEP fluxes at Mars. SEP ion precipitation is an important source of heating, ionization, and chemical changes in the upper atmosphere of Mars and may have played a substantial role in driving atmospheric escape over the history of the solar system. Here we examine SEP fluxes during a series of solar disturbances in late February through early March 2015. We present the first SEP ion pitch angle distributions measured at Mars and show how SEP anisotropy changes over the course of the event period. We present examples and explanations of several different kinds of variability in the SEP flux measured in the four fields of view of the instrument. Finally, we present a statistical study of energy‐ and angle‐dependent shadowing of SEP under three different sets of heliospheric conditions, showing that the direct shadowing of SEP by the solid planet may be better explained in terms of simple geometry under quieter heliospheric conditions. In‐depth understanding of the effects on SEP fluxes and precipitation patterns by the complex interplay between solar wind disturbances and Mars' magnetospheric configuration awaits detailed modeling studies. Pitch angle anisotropy of SEP ions at Mars varies with heliospheric conditionsVariability in MAVEN SEP ion measurements has several different nonheliospheric causesBlockage (i.e., shadowing) of energetic ions by Mars is energy dependent and highly variable

We study the solar wind interaction with the Martian upper atmosphere during the 8 March 2015 interplanetary coronal mass ejection (ICME) by using a global multifluid MHD model. Comparison of the simulation results with observations from Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft shows good agreement. The total ion escape rate is increased by an order of magnitude, from 2.05 × 1024s−1(pre‐ICME phase) to 2.25 × 1025s−1(ICME sheath phase), during this time period. Two major ion escape channels are illustrated: accelerated pickup ion loss through the dayside plume and ionospheric ion loss through the nightside plasma wake region. Interestingly, the tailward ion loss is significantly increased at the ejecta phase. Both bow shock and magnetic pileup boundary (BS and MPB) locations are decreased from (1.2RM, 1.57RM) at the pre‐ICME phase to (1.16RM, 1.47RM), respectively, during the sheath phase along the dayside Mars‐Sun line. Furthermore, both simulation and observational results indicate that there is no significant variation in the Martian ionosphere (at altitudes ≲ 200 km, i.e., the photochemical region) during this event. The total ion escape rate is increased by an order of magnitude during the 8 March ICMEThe tailward ion loss is significantly increased at the ejecta phaseThere is no significant variation in the Martian ionosphere (at altitudes ≲ 200 km)

Abstract—Intense magnetic anomalies over Martian surface suggest preservation of large volumes of very old crust (>3 Gyr) that formed in the presence of a global magnetic field. The global distribution of the magnetic intensities observed above the Martian crust suggests a division into three zones. Zone 1 is where the magnetic signature is negligible or of relatively low intensity at Mars Global Surveyor (MGS) satellite mapping altitude (400 km). Zone 2 is the region of intermediate crustal magnetic amplitudes and zone 3 is where the highest magnetic intensities are measured. Crater demagnetization near zone 3 reveals the presence of rocks with both high magnetic intensity and coercivity. Magnetic analyses of terrestrial rocks show that compositional banding in orogenic zones significantly enhances both magnetic coercivity and thermal remanent magnetization (TRM) efficiency. Such enhancement offers a novel explanation for the anomalously large intensities inferred of magnetic sources on Mars. We propose that both large magnetic coercivity and intensity near the South Pole is indicative of the presence of a large degree of deformation. Associated compositional zoning creates conditions for large scale magnetic anisotropy allowing magnetic minerals to acquire magnetization more efficiently, thereby causing the distinct magnetic signatures in zone 3, expressed by intense magnetic anomalies. We use a simple model to verify the magnetic enhancement. We hypothesize that magnetically enhanced zone would reside over the down welling plume at the time of magnetization acquisition.