Katsavrias, Ch ; Sandberg, I ; Li, W ; Podladchikova, 0 ; Daglis, I ; Papadimitriou, C ; Aminalragia-Giamini, S

published in Journal Geophysical Research, Volume 124 issue Issue 6, pp. p 4402-4413

Abstract: We report observations of energetic electron flux and Phase Space Density (PSD) to show that a relatively weak magnetic storm with Sym − Hmin ≈ −50nT, resulted in a relativistic and ultra–relativistic electron enhancement of two orders of magnitude similar to the St.Patrick’s event of 2015, an extreme storm with Sym − Hmin ≈ −235nT. This enhancement appeared at energies up to ≈ 8 MeV, lasted for at least 24 days and was not recorded in geosynchronous orbit where most space weather alert data are collected. By analyzing radial profiles of PSD we show that the enhancement of relativistic and ultra–relativistic electrons is caused by different mechanisms: first, chorus waves during the intense substorm injections of April 21–25 accelerate the seed electron population to relativistic energies and redistribute them while inward diffusion driven by Pc5 ULF waves further accelerates them to ultra–relativistic energies.

Keyword(s): Long–lasting multi–MeV electron enhancement during a period of a relatively weak ; geomagnetic storm. ; Electron seed population was accelerated to relativistic energies by the enhanced chorus waves. ; Relativistic electrons were further accelerated up to 8 MeV by inward diffusion.
DOI: 10.1029/2019JA026743
Links: link