Study on geomagnetic storms driving motion of 0.1–2 MeV radiation belt electrons

Abstract

Using more than five years’ worth of data observed by the Instrument for the Detection of Particles (IDP) spectrometer onboard the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) satellite, we studied the motion characteristics of energetic electrons in different regions, i.e., the inner radiation belt, the outer radiation belt, and the slot region in geomagnetic storms. We investigated the flux change of 0.1–2.4MeV electrons and the energy change of 0.1–1.0MeV electrons in these different regions. By cross correlation analysis, we came to the following conclusions. First, when Dst<−50, the correlation coefficient (c.c.) of the electron flux and Dst index ranges from −0.63 to −0.86, and the enhancement of the electron flux generally occurs during the storm’s main and recovery phases. Second, the storms greatly influence the lower energy region of the electron energy spectrum in the inner radiation belt, while the enhancement in the higher energy region is more significant in the outer radiation belt and the slot region. Third, the effects of geomagnetic storms on electrons are not distinguished significantly between in the day and night, and independent of the timing of the events. For storms with −50<Dst<−30, there is a negative correlation of −0.51 to −0.57 between the Dst index and the electron flux in the outer radiation belt. Our analysis suggests that strong storms cause energetic electron ejections across a wide range, and the ejection level is affected by the storm intensity. Furthermore, the electron energy region influenced by the strong geomagnetic storms is opposite in the inner and outer radiation belts. The proportion of electrons accelerated to relativistic energies is greater in the outer radiation and slot regions, while the ejection energetic electrons are more concentrated in the low energy region of the inner radiation belt. This phenomenon reflects the different electron injection mechanisms and accelerating processes responsible for spectral index variations in different L regions during geomagnetic storms.