Effects of solar irradiance on the upper ionosphere and oxygen ion escape at Mars: MAVEN observations

Abstract

AbstractWe present multi‐instrument observations of the effects of solar irradiance on the upper Martian ionosphere and escape fluxes based on the Mars Atmosphere and Volatile EvolutioN (MAVEN) data from November 2014 to February 2016. It is shown that fluxes of oxygen ions with E > 30 eV both inside and outside of the Martian magnetosphere are nonsensitive to EUV variations. In contrast, the fluxes of ions with lower energies extracted from the upper ionosphere increase with solar irradiance. Such an enhancement is nonlinear with the EUV variations and exhibits a growth by almost 1 order of magnitude when the EUV (0.1–50 nm) radiation increases to ≥0.1 W/m2 implying an enhancement of total ion losses of the low‐energy component to ∼1.8·1025 s−1. The flow of cold ions in the near‐Mars tail occurs very asymmetrical shifting in the direction opposite to the direction of the solar wind motional electric field. Fluxes of the low‐energy (E≤30 eV) ion component are also nonsensitive to the variations in solar wind dynamic pressure.