Analysis of Ground Level Enhancements (GLE) : Extreme solar energetic particle events have hard spectra

Show simple item record Asvestari, E. Willamo, T. Gil, A. Usoskin, I. G. Kovaltsov, G. A. Mikhailov, V. V. Mayorov, A. 2019-12-10T12:47:01Z 2019-12-10T12:47:01Z 2017-08-15
dc.identifier.citation Asvestari , E , Willamo , T , Gil , A , Usoskin , I G , Kovaltsov , G A , Mikhailov , V V & Mayorov , A 2017 , ' Analysis of Ground Level Enhancements (GLE) : Extreme solar energetic particle events have hard spectra ' , Advances in Space Research , vol. 60 , no. 4 , pp. 781-787 .
dc.identifier.other PURE: 122406663
dc.identifier.other PURE UUID: f5f8cf83-729e-4e7f-940f-00d3a17e0a86
dc.identifier.other WOS: 000405975700004
dc.identifier.other Scopus: 85011301733
dc.description.abstract Nearly 70 Ground Level Enhancements (GLEs) of cosmic rays have been recorded by the worldwide neutron monitor network since the 1950s depicting a big variety of energy spectra of solar energetic particles (SEP). Here we studied a statistical relation between the event-integrated intensity of GLEs (calculated as count-rate relative excess, averaged over all available polar neutron monitors, and expressed in percent-hours) and the hardness of the solar particle energy spectra. For each event the integral omnidirectional event integrated fluences of particles with energy above 30 MeV (F-30) and above 200 MeV (F-200) were computed using the reconstructed spectra, and the ratio between the two fluences was considered as a simple index of the event's hardness. We also provided a justification of the spectrum estimate in the form of the Band-function, using direct PAMELA data for GLE 71 (17-May-2012). We found that, while there is no clear relation between the intensity and the hardness for weak events, all strong events with the intensity greater 100 % h are characterized by a very hard spectrum. This implies that a hard spectrum can be securely assumed for all extreme GLE events, e.g., those studied using cosmogenic isotope data in the past. (C) 2016 COSPAR. Published by Elsevier Ltd. All rights reserved. en
dc.format.extent 7
dc.language.iso eng
dc.relation.ispartof Advances in Space Research
dc.rights cc_by_nc_nd
dc.rights.uri info:eu-repo/semantics/openAccess
dc.subject Solar energetic particles
dc.subject Cosmic rays
dc.subject PROTON EVENTS
dc.subject SPACE
dc.subject CYCLE
dc.subject 115 Astronomy, Space science
dc.title Analysis of Ground Level Enhancements (GLE) : Extreme solar energetic particle events have hard spectra en
dc.type Article
dc.contributor.organization Department of Physics
dc.description.reviewstatus Peer reviewed
dc.relation.issn 0273-1177
dc.rights.accesslevel openAccess
dc.type.version acceptedVersion

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