Precipitation of accelerated electrons at Mars

Accelerated electron populations observed in the nightside ionosphere of Mars are investigated by utilizing measurements obtained by the Solar Wind Electron Analyzer aboard the MAVEN spacecraft. The measurements are of particular interest as they extend to altitudes as low as 130 km, allowing us to investigate the degree to which the accelerated populations precipitate into the Martian upper atmosphere and cause ionization. The spectral features of the accelerated electron populations suggest that a large fraction of these electron populations originate from a cold plasma with electron temperature as low as 1 eV. The peak energy of the accelerated electrons is generally found in the range of tens to hundreds of eV. Electrons in this energy range have been previously suggested as the cause of the discrete aurora emissions observed on Mars. Finally, we find that even though the detection rate of the accelerated electrons is small (<1%), they account for ~10% of the total energy that is deposited into the nightside ionosphere by electron precipitation.