Geographic variation in Earth's core magnetic field modifies the
radiation belt electron flux relationship with substorms, ULF waves, and
solar wind drivers
Abstract
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.
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. Controlling for Earth’s geographic
|B| variability, particularly at lower L shells,
results in stronger correlations between electron flux and solar wind,
substorm, and ULF wave drivers. 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 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.