Inner magnetospheric electric fields from the SWMF

This study presents a comparison of electric fields from the Space Weather Modeling Framework (SWMF) with observations from various spacecraft. The electric field at the equatorial plane (minimum magnetic field surface) in the inner magnetosphere is relatively low, well below 1 mV/m, during quiet times, but can be quite large, approaching 10 mV/m, during geomagnetic storm intervals. The largest fields are sometimes observed on the Earthward side of the plasma pressure peak, quite close to Earth. Furthermore, off-equatorial electric field values scale with the magnetic field and quickly increase to even larger values. Not only can the potential electric field get altered due to localized pressure peaks and associated field-aligned current structures, but also inductive electric fields are known to substantially contribute to the full electric field experienced by inner magnetospheric particles. While the SWMF produces good comparison with geomagnetic indices during storms, the electric fields within geosynchronous orbit have not received much scrutiny. We present simulation results investigating the SWMF near-Earth electric field spatial structure and temporal development during storm intervals. Comparisons are made against electric field measurements from various spacecraft, like the Van Allen Probes, THEMIS (Time History of Events and Macroscale Interactions during Substorms), and MMS (Magnetospheric Multi-Scale).