Spectra of relativistic solar proton ground-level events recorded at Sanae, Antarctica

Ten solar proton flare enhancements of more than 5 percent have been recorded at Sanae (70 deg S, 2 deg W) at a cutoff rigidity of 0.86 GV during the last two decades, by both a super neutron monitor and a four-counter neutron-moderated detector. The relative enhancements as recorded by these detectors for different solar flares are summarized and are related to the steepnesses of the relativistic solar flare proton spectra. Variability in the ratio of the relative enhancements observed may be due to a changing energy-dependent release of the protons from the solar flare region or corona, or from changing irregularities in the interplanetary magnetic field. 19 refs