GLE and sub-GLE redefinition in the light of high-altitude polar neutron monitors
Poluianov, S. V.; Usoskin, I. G.; Mishev, A. L.; Shea, M. A.; Smart, D. F. (2017-11-13)
Poluianov, S.V., Usoskin, I.G., Mishev, A.L. et al. Sol Phys (2017) 292: 176. https://doi.org/10.1007/s11207-017-1202-4
This is a post-peer-review, pre-copyedit version of an article published in Solar Physics. The final authenticated version is available online at: http://dx.doi.org/10.1007/s11207-017-1202-4.
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.
- Avoin saatavuus