Characteristics of solar X-ray flares and their effects on the ionosphere and human exploration to Mars: MGS radio science observations

Abstract

Responses of solar X-ray flares were observed in a layer of the Martian ionosphere at altitudes of ~110 km from 32 electron density profiles obtained by radio science experiment onboard Mars Global Surveyor (MGS) during solar cycle 23. Of the 32 profiles recorded during flare periods, 10 were associated with X-class flares, 12 with M class and 10 with C class flares. The flare E-peak densities vary with solar X-ray flux, Solar Zenith Angle (SZA), Solar Longitude (Ls) and latitudes. Ionospheric Electron Content (IEC) and E-peak electron production rates of these flare profiles are estimated in the E region ionosphere. We found a maximum increase of ~200%, ~140% and ~90% in the time series of IEC for X, M and C class flares respectively. The dependence of flare E-peak electron production rate with Ls is fitted by a sinusoidal function. We have also calculated biological doses ~0.1–1.0 × 10⁻¹, 1–8 × 10⁻³ and 1–6 × 10⁻⁴ Gy for X, M, C class flares respectively to study the human risk for exploration to Mars. Among 10 X-class flares X1 is a strong solar flare that gives highest dose, which is potentially lethal for human risk in Mars' space.