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.
This is a preview of subscription content, log in to check access.
Buy single article
Instant access to the full article PDF.
Price includes VAT for USA
Subscribe to journal
Immediate online access to all issues from 2019. Subscription will auto renew annually.
This is the net price. Taxes to be calculated in checkout.
Aguilar, M., Aisa, D., Alpat, B., Alvino, A., Ambrosi, G., Andeen, K., et al.: 2015, Precision Measurement of the Proton Flux in Primary Cosmic Rays from Rigidity 1 GV to 1.8 TV with the Alpha Magnetic Spectrometer on the International Space Station. Phys. Rev. Lett. 114, 171103. DOI .
Atwell, W., Tylka, A.J., Dietrich, W., Rojdev, K., Matzkind, C.: 2015, Sub-GLE Solar Particle Events and the Implications for Lightly-Shielded Systems Flown During an Era of Low Solar Activity. In: Int. Conf. Environ. Sys., Lunar Planet. Sci. Conf. Proc. ntrs.nasa.gov/search.jsp?R=20150009484 .
Dorman, L.: 2004, Cosmic rays in the Earth’s atmosphere and underground, Kluwer Academic, Dordrecht. 1-4020-2071-6.
Flückiger, E.O., Moser, M.R., Pirard, B., Bütikofer, R., Desorgher, L.: 2008, A parameterized neutron monitor yield function for space weather applications. In: Caballero, R., D’Olivo, J.C., Medina-Tanco, G., Nellen, L., Sánchez, F.A., Valdés-Galicia, J.F. (eds.) Proc. 30th Int. Cosmic Ray Conf. 1, 289. ADS .
Grieder, P.K.F.: 2001, Cosmic Rays at Earth, Elsevier Science, Amsterdam. ADS .
Mishev, A.L., Kocharov, L.G., Usoskin, I.G.: 2014, Analysis of the ground level enhancement on 17 May 2012 using data from the global neutron monitor network. J. Geophys. Res., Space Phys. 119(2), 670. DOI .
Mishev, A., Poluianov, S., Usoskin, I.: 2017, Assessment of spectral and angular characteristics of sub-GLE events using the global neutron monitor network. J. Space Weather Space Clim. 7, A28. DOI .
Nevalainen, J., Usoskin, I., Mishev, A.: 2013, Eccentric dipole approximation of the geomagnetic field: Application to cosmic ray computations. Adv. Space Res. 52(1), 22. DOI .
Picozza, P., Galper, A.M., Castellini, G., Adriani, O., Altamura, G., Ambriola, M., et al.: 2007, PAMELA – a payload for antimatter matter exploration and light-nuclei astrophysics. Astropart. Phys. 27(4), 296. DOI .
Poluianov, S., Usoskin, I., Mishev, A., Moraal, H., Kruger, H., Casasanta, G., Traversi, R., Udisti, R.: 2015, Mini Neutron Monitors at Concordia Research Station, Central Antarctica. J. Astron. Space Sci. 32, 281. DOI . ADS .
Raukunen, O., Vainio, R., Tylka, A.J., Dietrich, W.F., Jiggens, P., Heynderickx, D., Dierckxsens, M., Crosby, N., Ganse, U., Siipola, R.: 2017, Two solar proton fluence models based on ground level enhancement observations. J. Space Weather Space Clim., submitted.
Simpson, J.A.: 1990, Astrophysical Phenomena Discovered by Cosmic Ray and Solar Flare Ground Level Events: The Early Years. In: Proc. Int. Cosmic Ray Conf. 12, 187. ADS .
Smart, D.F., Shea, M.A.: 2009, Fifty years of progress in geomagnetic cutoff rigidity determinations. Adv. Space Res. 44(10), 1107. DOI .
Souvatzoglou, G., Mavromichalaki, H., Sarlanis, C., Mariatos, G., Belov, A., Eroshenko, E., Yanke, V.: 2009, Real-time GLE alert in the ANMODAP Center for December 13, 2006. Adv. Space Res. 43(4), 728. Solar Extreme Events: Fundamental Science and Applied Aspects. DOI .
Tylka, A.J., Dietrich, W.F.: 2009, A new and comprehensive analysis of proton spectra in ground-level enhanced (GLE) solar particle events. In: Proc. 31th Int. Cosmic Ray Conf., Lodz. icrc2009.uni.lodz.pl/proc/pdf/icrc0273.pdf .
Vashenyuk, E.V., Balabin, Y.V., Stoker, P.H.: 2007, Responses to solar cosmic rays of neutron monitors of a various design. Adv. Space Res. 40(3), 331. DOI .
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). We acknowledge Askar Ibragimov for the support of the International GLE database ( gle.oulu.fi ) and are grateful to the worldwide neutron-monitor database ( nmdb.eu ), which is a product of an EU Project. We thank Marc Duldig, Erwin Flückiger, John Humble, and Roger Pyle for valuable discussions.
Disclosure of Potential Conflicts of Interest
The authors declare that they have no conflicts of interest.
About this article
Cite this article
Poluianov, S.V., Usoskin, I.G., Mishev, A.L. et al. GLE and Sub-GLE Redefinition in the Light of High-Altitude Polar Neutron Monitors. Sol Phys 292, 176 (2017). https://doi.org/10.1007/s11207-017-1202-4
- Energetic particles