Variability of relativistic electron flux (E > 2 MeV) during geo-magnetically quiet and disturbed days: a case study

We analyzed the relativistic electron fluxes (E > 2 MeV) during five different geomagnetic storms: moderate, intense, super-intense, ICME HILDCAA (High-Intensity Long Duration Continuous Aurora Activity), non-storm HILDCAA and a geo-magnetically quiet period. We have opted for continuous wavelet (CWT) analysis techniques to comprehend the periodicity and dynamics of relativistic electron fluxes during storm conditions. The findings of CWT revealed the smooth and periodic trend of relativistic electrons during geo-magnetically quiet periods of 25 January 2007. In contrast, the dominant frequencies associated with the oscillations of relativistic electrons are observed during the recovery phase of the geomagnetic storms. A noteworthy finding of the study is the discrepancies in key periodicities at a lower scale connected with the sudden enhancement of the relativistic electron flux during HILDCAAs and other geomagnetic storms. While a key periodicity at a lower scale is observed at moderate, intense and super intense storms during the recovery phases of the storms, the HILDCAAs events exhibit high-frequency behaviour during both main and recovery phases. Our result substantiates that a geomagnetic storm is not the primary factor that pumps up the radiation belt. The geomagnetic storms can deplete, enhance or cause little effect on the outer radiation belt. To be precise, it exhibits event-specific behaviour. Additionally, we performed Multiresolution Analysis (MRA) to observe temporal distribution characteristics of relativistic electron flux using wavelet decomposition and reconstruction. MRA revealed the diurnal pattern of relativistic electrons flux for the quiet period of the magnetosphere, as depicted by the details and approximations coefficients. On the other hand, the relativistic electron enhancements during several geomagnetic storms are closely related to the presence of high-speed solar wind streams and southward IMF during the recovery phase of a geomagnetic storm.