High‐Latitude Electrodynamics and Thermospheric Density Variations During the 2024 Gannon Storm

Abstract This study investigates high‐latitude electrodynamics and thermospheric density variations during the 2024 Gannon's storm. First, the auroral precipitation module of Auroral Spectra and High‐Latitude Electric field variabilitY, ASHLEY‐A, is improved to more accurately capture the location of auroral precipitation observed during this superstorm. The improved ASHLEY‐A is then used to specify the electron precipitation in the Global Ionosphere Thermosphere Model (GITM). Two GITM simulations are performed which are different in their specifications of high‐latitude electric potential. One using field‐aligned current measurements from the Active Magnetosphere and Planetary Electrodynamics Response Experiment data set, and the other employing the Weimer empirical model. Results show that the FAC‐driven GITM simulation more accurately captures high‐latitude electric field than the Weimer model, leading to a better capture of high‐latitude Joule heating inputs and a more effective reproduction of storm‐time thermospheric density variations compared to the Weimer‐driven simulation. Finally, this study focuses on the formation of intense high‐latitude neutral density spikes observed in the Southern Hemisphere between 03:00 and 06:00 universal time on May 11. FAC‐driven GITM simulation reveals that these spikes are associated with a localized density hotspot driven by strong upward winds. Notably, the upward winds are not collocated with regions of intense Joule heating. Instead, the winds appear to result from strong horizontal wind divergence, likely influenced by enhanced Joule heating in adjacent regions. These findings highlight the importance of using more realistic high‐latitude drivers in thermospheric simulations and the complex processes that shape high‐latitude thermospheric variations.