A comparison of proton activity in cycles 20–23

Abstract

The solar proton singularities in cycles 20–23 were compared. For such a comparison, it is of special importance to present information about solar proton events (SPEs) uniformly. The Katalog working group, including representatives of different institutions, created SPE catalogs for 1970–2010. These catalogs include solar events with E ≥ 10 MeV proton fluxes exceeding 1 cm−2 s−1 sr−1 near the Earth. The various conditions that accompany SPEs result in a considerable scatter of the flux parameters and energy spectra and in a difference in time profiles. Regularities in the distribution of these parameters during four solar activity cycles can be specifically revealed only based on a statistical approach that is used in this work. In this case a comparison can be successful only when the analyzed data series are homogeneous. Solar activity singularities during the entire period of SPE measurements (from cycle 19 to the end of cycle 23) are described. The methods for adjusting solar events in particles that are registered near the Earth to solar sources are of special importance. These statistical data suggest that the number of SPEs in the cycles and the event distribution within a solar cycle may indicate that the SPE generation character is different in cycles 20–21 and 22–23.