The effects of different solar flare characteristics on the global thermosphere

Given the ability of global models of the upper atmosphere to utilize high-resolution solar spectra to specify the solar soft X-ray and EUV irradiance, researchers now have the ability to perform detailed theoretical analysis of the response of the upper atmosphere to dynamic solar forcing more completely than ever before. Therefore, it is possible to develop a more quantitative understanding of the response of the thermosphere to solar flares. In this study, the effect of different characteristics of solar flares on the thermosphere is investigated. This is done in a theoretical manner, using synthetic solar irradiance data that is based on observations as input to the global ionosphere-thermosphere model (GITM). Specifically, the neutral response to the total incident energy, peak flare magnitude, background irradiance magnitude, duration of the impulsive phase, and decay time is investigated. It is found that the density response at 400 km altitude is linearly dependent on the total integrated energy above the background level being deposited into the atmosphere, and that the day-side response is strongly dependent on both the total incident energy into the system and the peak flare magnitude. Also, the decay time of the flare is important in determining the time at which the maximum global response occurs. Finally, the duration of the impulsive phase is found to have little effect on the global response of the system.

► We model the response of the thermosphere to different solar flare characteristics.
► The total integrated energy above background is linearly related to the average thermospheric response.
► The decay time of the flare determines the timing of the average thermospheric response.
► The duration of the impulsive phase has little effect on the response.