Spatial Geographic Variation in Earth's Core Magnetic Field Modifies the Radiation Belt Electron Flux Relationship With Substorms, ULF Waves, and Solar Wind Drivers

Abstract Spatial geographic variability in Earth's core magnetic field, measured at 400 km altitude but corrected for ionospheric and magnetospheric signals, correlates with electron flux levels measured by the RBSP spacecraft. A higher Earth's |B| magnitude results in lower flux over L2‐6. Over 20 eV–2 MeV, at L2‐4, this negative correlation is as large as −0.21, peaking at the 158 keV electrons, with the strongest effects in the 71 keV–2 MeV electrons. Despite higher L shells being well above the 400 km field measure, statistically significant correlation with the core field was still seen in higher energy 1–2 MeV electrons over L5‐6. Adding Earth's geographic |B| variability as a covariate in regression or ARMAX analyses, particularly at lower L shells, results in stronger correlations between electron flux and solar wind, substorm, and ULF wave drivers, with possible nonlinearity in the associations accounted for by taking logs of the variables. At L2, substorms (measured by the SME index), ULF waves, and solar wind velocity show increased correlations with electron flux (30%, 100%, and 175%, respectively) when Earth's |B| is added as a covariate to the ARMAX regression models. Modest increases in correlation of electron flux with these possible drivers were also seen at L3‐6. This argues for the addition of Earth's |B| as a covariate in models of electron response to drivers.