12-20 July 2017
Asia/Seoul timezone
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BEXCO - Room F(201/202/203/204)

[SH065] Analysis of Ground-Level Enhancements: Strong events are hard


  • Ilya USOSKIN

Primary authors



Ground Level Enhancements (GLEs) recorded by neutron monitor detectors are characterized by a variety of energy spectra of solar energetic particles (SEP), which vary between soft (as in August 1972) and hard (February 1956). The aim of this work is to investigate the statistical relation between the hardness of the energy spectra and the event-integrated intensity. We calculated the event-integrated omnidirectional fluence of protons above 30MeV (F30) and above 200MeV (F200) using energy spectra reconstructed from both ground-based and space-borne data. The use of the Band-function for the spectra approximation was justified using direct PAMELA measurements of the GLE 71, which occurred in 17 of May 2012. The ratio of the F30-to-F200 fluences is considered as an index of the hardness of the events spectra. The main results of this study is that all strong events (intensity greater 100 %*hr) are characterized by a very hard spectrum, while weak and moderate events do not show any clear pattern between the hardness and the intensity of the event.