[PPS08-01] On possibility of visualization of Martian space environment with diffuse aurora: Relations between magnetic field structure and solar energetic electron penetration into the upper atmosphere observed by MAVEN
Keywords:aurora, space weather, magnetic field structure
In this study, we investigated three SEP events observed by MAVEN in December 2014, March 2015, and September 2017. The pitch angle (PA) distributions of the high-energy (30-210 keV) electrons observed in the Martian ionosphere are analyzed in details. In order to achieve a good coverage in the 2-D (PA-energy) phase space, data obtained during a SEP event is accumulated and binned. Using the elevation angle of the local magnetic field, we also sorted the data so as to investigate the SEP electron loss below the MAVEN periapsis (~150 km altitude). The obtained PA distributions in the ionosphere are compared with the distributions of the source electrons in the magnetosheath. The results show that the field-aligned component is pronounced for the penetrating electrons and it does not significantly depend on the initial PA distributions in the magnetosheath. The observation also indicates that the highest energy of the SEP electrons lost into the Martian atmosphere depends on the magnetic field configuration draped around the planet. The SEP electron loss into the atmosphere is larger in higher SZA, suggesting the deeper penetration of draped magnetic fields in the nightside than dayside. These results support the scenario that the solar energetic electrons penetrate into the ionosphere along the draped magnetic field and the altitude to which they can penetrate depends on the magnetic field configuration. In other words, global diffuse aurora observations can give a new tool to visualize Martian space environment for understanding interaction between the solar wind and Martian upper atmosphere, especially the dynamics of the nightside ionosphere.
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