Dipolarization Events With Inductive, Radial Electric Fields Observed by Van Allen Probes

Abstract

Dipolarization events with inductive, radial electric fields are examined, using Van Allen Probes data between 2013 and 2018. Two cases are studied, followed by statistical analyses. These events were observed between evening and premidnight magnetic local times (MLTs) under moderate geomagnetic activities. Radial electric field variations, azimuthal magnetic field variations, and energetic protons were often observed when horizontal magnetic fields started to decrease in the dip region. Magnetic field lines were stretched with their motion similar to the gradient B/curvature drift velocities of energetic protons. Signs of electric fields changed when horizontal magnetic fields started to increase in the dipolarization front (DF). Electric field variations were correlated with magnetic field ones with ˜90 deg. phase shift. These observations are mainly interpreted in terms of energetic proton structures drifting toward the probe locations, while being accompanied by standing waves.

Dipolarization Events With Inductive, Radial Electric Fields Observed by Van Allen Probes

“…OMNI data are available at https://omniweb.gsfc.nasa.gov/ (Papitashvili & King, 2020). The data analysis software for this study is available on Zenodo (Matsui & Farrugia, 2023).…”