Abstract Solar extreme ultraviolet (EUV, 10–100 nm) and X‐ray (<10 nm) photons are the primary ionization source for the dayside Mars ionosphere. Their fluxes, especially at short wavelengths, increase significantly during solar flares. Among the series of solar flares and solar storms encountered by Earth and Mars in May 2024, one of the strongest solar flares occurred on 20 May 2024 when the Mars Atmospheric and Volatile EvolutioN (MAVEN) spacecraft was entering the Mars ionosphere. This event provides a unique opportunity to study the Mars ionospheric response to the onset and early phase of an extremely intense flare. This study utilizes two particle measurements onboard MAVEN to infer the flare timeline and a flare class of X12.8. The observed main ionospheric response is the increased density at ∼400 km altitude at the flare onset and at ∼300 km altitude near the flare peak.
Xu et al. (Fri,) studied this question.