Characteristics of relativistic solar cosmic rays during the event of December 13, 2006

Abstract

The characteristics of relativistic solar protons have been obtained using the methods of optimization based on the data of ground detectors of cosmic rays during the event of December 13, 2006, which occurred under the conditions of solar activity minimum. The dynamics of relativistic solar protons during the event has been studied. It has been indicated that two populations (components) of particles exist: prompt and delayed (slow). The prompt component with a hard energy spectrum and strong anisotropy manifested itself as a pulse-shaped enhancement at Apatity and Oulu stations, which received particles with small pitch-angles. The delayed component had a wider pitch-angle distribution, as a result of which an enhancement was moderate at Barentsburg station and at most neutron monitors of the worldwide network. The energy spectra obtained from the ground-based observations are in good agreement with the direct measurements of solar protons on balloons and spacecraft.