Energetic particle acceleration during a major magnetic storm Original Research Article

We study the global properties of energetic (>30 keV) particles during the main and early recovery phase of a major magnetic storm of March 31, 2001, using data of the NOAA 15 and 16 and the CLUSTER satellites. During the storm main phase the ring current energetic electron and ion fluxes were increased by nearly two orders of magnitude, and the flux maxima were shifted to below L = 3. The maximum ion fluxes were observed at about 07 UT, coinciding with the minimum Dst. However, the highest fluxes of energetic electrons were observed only at about 16–18 UT, indicating significant differences in the acceleration of energetic electrons and ions during the storm. We suggest that the ion maximum at about 07 UT was due to field-aligned acceleration of ions from the ionosphere whereas the electron maximum at 16–18 UT was due to a large injection from the nightside.