Effects of Interplanetary Structures on the Earth's Outer Radiation Belt Dynamics Observed During September 12-26, 2014: I) Coronal Mass Ejection

Solar wind variations and magnetospheric processes result in a dynamic electron population within the outer Van Allen radiation belt, where electron energies range from several 10's to several 1000's KeV . Geomagnetic storms and various solar wind-magnetosphere interaction processes including convection cause both dramatic particle flux increase or decreases. Here we analyze the occurrence of a drop out of ~ 0.04 - 4.5 MeV electron fluxes measured by NASA's Van Allen Probes, THEMIS and NOAA's GOES during a magnetic cloud-driven geomagnetic storm which started at September 12, 2014. The ~3-day storm left a steady low flux of outer belt energetic electrons that lasted for twelve days (Figure 1). At higher energy levels, electron fluxes decreased by ~1 order of magnitude throughout the vast region from L* ~3 to 6.6. Simulation of a 2 MeV relativistic electron orbit, with 90◦ pitch angle, during the most compressed magnetosphere period shows that magnetopause shadowing can be responsible for the electron dropout observed at radial distances larger than ~ 6 RE). Wave-particle interaction are associated with loss occurring at L < 4. We discuss the solar wind drivers, in particular the contribution of the magnetic cloud parameters for magnetospheric dynamics during the whole period analyzed, i.e., September 13-24, 2014.