Modeling the Impact of a Strong X-Class Solar Flare on the Planetary Ion Composition in Mercury's Magnetosphere

We model the impact of an extreme solar flare on the Mg⁺, Na⁺, O⁺ and He⁺ ion density distribution in Mercury's magnetosphere. The Flare Irradiance Spectral Model of the solar irradiance during the X9.3-class flare on 6 September 2017 is used as input to the time-dependent Latmos Ionized Exosphere ion density model. We find that the time-evolution of the planetary ion distribution differs with respect to energy, location and species. There exist two ion energy populations on the dayside that experience different dynamical evolution. The peak ion density in the nightside plasma sheet is delayed by ∼7-8 min compared to the dayside. The maximum Mg⁺ density occurs ∼4 min before He⁺ and O⁺ in the whole magnetosphere. The time delay between different species does not necessarily occur for solar flares that erupt near the apparent solar limb, where the optical depth is large.