Determining the instant of acceleration of protons responsible for the onset of ground-level enhancements of solar cosmic rays

Abstract

The aim of this work is to determine the instant of acceleration at the Sun of protons responsible for the onset of the ground-level enhancements (GLEs). Using a set of data on peak soft X-ray intensity derivatives and hard X-ray and gamma radiation intensities along with radio burst intensities in the cm/mm range, we the time interval of the maximum solar energy release for flares associated with 45 GLEs (27 through 71). We also determined the times of GLE onset for the same events. In 31 events, the time of GLE onset lagged 2–15 minutes behind the observed maximum of flare energy release. Such brief lags suggest that the effective acceleration of the protons responsible at least for the onset of GLEs occurs typically within the time interval of maximum flare energy release.