University of Oulu

Poluianov, S.V., Usoskin, I.G., Mishev, A.L. et al. Sol Phys (2017) 292: 176.

GLE and Sub-GLE redefinition in the light of high-altitude polar neutron monitors

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Author: Poluianov, S. V.1,2; Usoskin, I. G.1,2; Mishev, A. L.1,2;
Organizations: 1Space Climate Research Unit, University of Oulu, Oulu, Finland
2Sodankylä Geophysical Observatory, University of Oulu, Oulu, Finland
3SSSRC, 100 Tennyson Avenue, Nashua, NH 03062, USA
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 0.2 MB)
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Language: English
Published: Springer Nature, 2017
Publish Date: 2018-11-13


The conventional definition of ground-level enhancement (GLE) events requires a detection of solar energetic particles (SEP) by at least two differently located neutron monitors. Some places are exceptionally well suitable for ground-based detection of SEP — high-elevation polar regions with negligible geomagnetic and reduced atmospheric energy/rigidity cutoffs. At present, there are two neutron-monitor stations in such locations on the Antarctic plateau: SOPO/SOPB (at Amundsen–Scott station, 2835 m elevation), and DOMC/DOMB (at Concordia station, 3233 m elevation). Since 2015, when the DOMC/DOMB station started continuous operation, a relatively weak SEP event that was not detected by sea-level neutron-monitor stations was registered by both SOPO/SOPB and DOMC/DOMB, and it was accordingly classified as a GLE. This would lead to a distortion of the homogeneity of the historic GLE list and the corresponding statistics. To address this issue, we propose to modify the GLE definition so that it maintains the homogeneity: A GLE event is registered when there are near-time coincident and statistically significant enhancements of the count rates of at least two differently located neutron monitors, including at least one neutron monitor near sea level and a corresponding enhancement in the proton flux measured by a space-borne instrument(s). Relatively weak SEP events registered only by high-altitude polar neutron monitors, but with no response from cosmic-ray stations at sea level, can be classified as sub-GLEs.

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Series: Solar physics
ISSN: 0038-0938
ISSN-E: 1573-093X
ISSN-L: 0038-0938
Volume: 292
Issue: 11
Article number: 176
DOI: 10.1007/s11207-017-1202-4
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: The work was supported by the projects of the Academy of Finland Centre of Excellence ReSoLVE (No. 272157), CRIPA and CRIPA-X (No. 304435), and by the Finnish Antarctic Research Program (FINNARP).
Academy of Finland Grant Number: 272157
Detailed Information: 272157 (Academy of Finland Funding decision)
304435 (Academy of Finland Funding decision)
Copyright information: This is a post-peer-review, pre-copyedit version of an article published in Solar Physics. The final authenticated version is available online at: