10 May 2024 Gannon Storm: Connecting Energy Flux With Field Aligned Currents and Cross Polar Cap Potential

A simulation of the 10 May 2024 geomagnetic storm is used to investigate the theory of cross polar cap potential (CPCP) saturation in Earth's magnetosphere‐ionosphere system. THEMIS B (ARTEMIS P1) satellite magnetic field and plasma measurements at lunar distance upstream in the solar wind drives the Space Weather Modeling Framework (SWMF) in the Geospace configuration. Observations from GOES 16 along with select ground‐based magnetic field measurements confirm simulation predictions of a polar cap expansion to 60 MLAT, and the AMPERE‐derived integrated field aligned current strength (FAC) agree with simulation results with an of 0.74. Despite strong solar wind driving (Solar wind electric field >40 mV/m, Solar wind energy flux >50 TW), neither the SWMF nor the empirical models saturate the CPCP. Direct measurements of the cross‐polar potential from DMSP are inconclusive, due to rapid variations in the driving conditions compared with the DMSP integration time. Breakdown of the relationship between the solar wind and CPCP within SWMF reveals a linear relationship between injected energy flux and integrated field aligned current strength after storm sudden commencement , and a highly linear relationship between integrated field aligned currents and CPCP at all times . The CPCP does not saturate because of the tight coupling of actual energy input, FAC strength, and CPCP.