Impact of ICME sheath planarity on Earth's outer radiation belt.

A planar magnetic structure refers to a compressed and ordered region in interplanetary space where magnetic field vectors are predominantly confined to a plane. Due to enhanced plasma parameters associated with them, they play a significant role in space weather dynamics. To examine their geoeffectiveness, we investigate the impact of planar and non-planar sheaths of Interplanetary Coronal Mass Ejections on the outer radiation belt electrons, using in-situ particle data from NASA’s Van Allen Probes mission. A superposed epoch analysis on electron flux data revealed a significant reduction in electron flux during planar sheath passages as compared to non-planar sheaths, possibly driven by stronger magnetospheric compression resulting in intensifying magnetopause shadowing. Notably, electron flux levels exhibit a significant post-passage increase, surpassing pre-passage levels three days later. For the first time, the efforts taken to highlight the interplay between planar sheath-driven magnetospheric compression and radiation belt dynamics offer new insights for improving space weather forecasting.