The dayside ionosphere of Mars observed by MAVEN NGIMS

Abstract

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has provided a unique opportunity to study the variability of the Martian upper atmosphere and ionosphere, as well as their interaction with the solar wind under various conditions. This study characterizes the large-scale spatial-temporal evolution of the dayside ionosphere as observed by the Neutral Gas and Ion Mass Spectrometer (NGIMS) onboard MAVEN. NGIMS measures the composition and structure of both the ions and neutrals in the upper ionosphere and thermosphere at altitudes below ~500 km. Thanks to the precessing orbit of MAVEN, NGIMS has accumulated millions of ion and neutral measurements over a wide range of spatial and temporal parameters. In this study, we present what we have learned from the NGIMS measurements during the first 3.5 Mars years (2015–2021), including the spatial and compositional variation of the median dayside ionosphere, the observed ionospheric peak layer at high solar zenith angles (SZAs), which complements the observations by previous missions at lower SZAs, and the variability of the topside ionosphere.