Local Time Dependence of Neutral and Plasma EUV-Forcing Response in the Low-Latitude Martian Ionosphere

The Martian ionospheric electron temperature is closely coupled to the neutral atmosphere below 200 km resulting in significant diurnal temperature variations. Warmer electron temperatures at dawn are similarly observed at Earth, but the temperature at Earth is more closely correlated to the ionospheric density while at Mars, the electron temperature is more correlated with the neutral atmospheric density. Accordingly, solar EUV intensity should play an important role in driving Martian ionospheric temperatures. Using 1.3 Martian years of MAVEN neutral density and electron density and temperature data, the effects of solar intensity on the variability of the dayside equatorial ionosphere and atmosphere are presented. Using the neutral gas and ion mass spectrometer and Langmuir probe data, we find a good correlation between estimates of electron cooling caused by neutral-electron collisions and the measured electron temperatures. Furthermore, this neutral cooling and the resulting electron temperature response are found to vary significantly with EUV at certain local times. Dawn/dusk asymmetries in both the neutral and electron data are also observed and discussed.