MAVEN Insights into the Precipitation of Solar Energetic Electrons in the Upper Atmosphere of Mars during the September 2017 ICME Event
Abstract
Solar Energetic Particles (SEPs) play an important role in the dynamics and evolution of the Martian atmosphere. Due to their much higher energies compared to solar wind plasma, solar energetic electrons and protons can easily penetrate through the Mars bow shock and precipitate directly into the atmosphere of Mars, leading to ionization, dissociation, excitation, energization, and possible escape of atmospheric species. The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission carries a Solar Energetic Particle (SEP) instrument that measures the energy spectrum of energetic electrons and ions in four different look-directions. MAVEN's elliptical orbit around Mars allows the SEP instrument to measure the flux of incoming SEPs at high altitudes near MAVEN's apoapse, where SEPs are not influenced by the atmosphere, and to also follow the precipitation of SEPs into the atmosphere down to 150 km near MAVEN's periapse. During the September 2017 Interplanetary Coronal Mass Ejection (ICME) event, the SEP instrument detected complex features of energetic electron precipitation, such as energy dispersions, non-gyrotropic distributions, and rapid changes in flux and direction of electrons, at energies ranging from 10 keV to 200 keV and at altitudes ranging from 150 km to 1000 km. The observed patterns of electrons can be associated with the complex structure of the magnetic field at Mars at the time of the ICME event. In this work, we present SEP instrument observations of precipitating electrons and attempt to model the measurements by back-tracing electron trajectories in background magnetic fields. The electrons are started at the position of MAVEN and in the direction of the SEP instrument's four fields of view. Two different sets of magnetic fields are utilized in the simulations. The first set is uniform fields assumed to be equal to the magnetometer measurements at the location of MAVEN with added crustal magnetic fields as electron trajectories are back-tracked near Mars. The second, more advanced background fields, are taken from Magneto-Hydro-Dynamic (MHD) simulations of the ICME event tuned to match the particle and fields observations of MAVEN. These model-data comparisons help us gain insights into the physics behind the precipitation patterns of solar energetic electrons at Mars and can also aid in constraining the topology of the magnetic field at Mars during the ICME event.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.P33H3514R
- Keywords:
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- 6005 Atmospheres;
- PLANETARY SCIENCES: COMETS AND SMALL BODIES;
- 6025 Interactions with solar wind plasma and fields;
- PLANETARY SCIENCES: COMETS AND SMALL BODIES;
- 6026 Ionospheres;
- PLANETARY SCIENCES: COMETS AND SMALL BODIES;
- 5435 Ionospheres;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS