Kathryn J. Fallows, Gabriel Gonzalez, Paul Withers, Zachary Girazian

The response of the Mars ionosphere to solar flares

During a flare, the increase in solar flux at X-ray and EUV wavelengths causes an enhancement in electron densities in planetary ionospheres. Here we identify and analyze a set of 12 Mars Global Surveyor (MGS) radio occultation electron density profiles which have been affected by solar flares. These profiles coincide with flares in GOES XL flux (0.1-0.8 nm), and exhibit electron densities which are significantly enhanced above the daily average, at altitudes where X-ray and EUV flux is absorbed. With an ensemble of flares and enhanced electron density profiles, we investigate the dependence of the ionospheric response on the enhancement in the solar flux at X-ray and EUV wavelengths, and on optical depth. We characterize the relationship between these quantities with a suitable function, and show that the flare-induced enhancement in electron density increases with increasing enhancement in solar flux and with increasing optical depth. We similarly analyze the results of a 1D photochemical model of the response of the Mars ionosphere to a solar flare. We show that the enhancement in model electron densities exhibits the same dependence on solar flux and optical depth as observed in the flare-affected MGS profiles.