Martian Thermospheric Response to an X8.2 Solar Flare on 10 September 2017 as Seen by MAVEN/IUVS

Abstract : We report the response of the Martian upper atmosphere to a strong X‐class flare on September 10, 2017 as observed by the Imaging Ultraviolet Spectrograph (IUVS) instrument aboard the Mars Atmosphere Volatile EvolutioN (MAVEN) mission. The solar flare peaked at 16:24 hrs UT and IUVS dayglow observations were taken about an hour after the flare peak. Retrieved temperatures from IUVS dayglow observations show a significant increase during the flare orbit, with a mean value of ∼270 K and a maximum value of ∼310 K. The retrieved temperatures during the flare orbit also show a strong latitudinal gradient, indicating that the flare induced heating is limited between low‐ and mid‐latitudes. During this event IUVS observed an ∼70% increase in the observed brightness of CO₂⁺ Ultraviolet Doublet and CO Cameron band emission at 90 km, where high‐energy photons (< 10 nm) deposit most of their energy.