GLE and Sub-GLE Redefinition in the Light of High-Altitude Polar Neutron Monitors


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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  1. 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 .

    ADS  Article  Google Scholar 

  2. 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. .

    Google Scholar 

  3. Clem, J.M., Dorman, L.I.: 2000, Neutron monitor response functions. Space Sci. Rev. 93, 335. DOI . ADS .

    ADS  Article  Google Scholar 

  4. Dorman, L.: 2004, Cosmic rays in the Earth’s atmosphere and underground, Kluwer Academic, Dordrecht. 1-4020-2071-6.

    Book  Google Scholar 

  5. Evenson, P., Bieber, J., Clem, J., Pyle, R.: 2011, South Pole Neutron Monitor Lives Again. In: Proc. Int. Cosmic Ray Conf. 11, 459. DOI . ADS .

    Google Scholar 

  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 .

    Google Scholar 

  7. Forbush, S.E.: 1946, Three Unusual Cosmic-Ray Increases Possibly Due to Charged Particles from the Sun. Phys. Rev. 70, 771. DOI . ADS .

    ADS  Article  Google Scholar 

  8. Forbush, S.E., Stinchcomb, T.B., Schein, M.: 1950, The Extraordinary Increase of Cosmic-Ray Intensity on November 19, 1949. Phys. Rev. 79, 501. DOI . ADS .

    ADS  Article  Google Scholar 

  9. Gopalswamy, N., Xie, H., Akiyama, S., Mäkelä, P.A., Yashiro, S.: 2014, Major solar eruptions and high-energy particle events during solar cycle 24. Earth Planets Space 66, 104. DOI . ADS .

    ADS  Article  Google Scholar 

  10. Grieder, P.K.F.: 2001, Cosmic Rays at Earth, Elsevier Science, Amsterdam. ADS .

    Google Scholar 

  11. 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 .

    ADS  Article  Google Scholar 

  12. 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 .

    ADS  Article  Google Scholar 

  13. Mishev, A., Usoskin, I.: 2016, Analysis of the Ground-Level Enhancements on 14 July 2000 and 13 December 2006 Using Neutron Monitor Data. Solar Phys. 291, 1225. DOI . ADS .

    ADS  Article  Google Scholar 

  14. 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 .

    ADS  Article  Google Scholar 

  15. 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 .

    ADS  Article  Google Scholar 

  16. 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 .

    ADS  Article  Google Scholar 

  17. 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.

  18. 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 .

    Google Scholar 

  19. Smart, D.F., Shea, M.A.: 2009, Fifty years of progress in geomagnetic cutoff rigidity determinations. Adv. Space Res. 44(10), 1107. DOI .

    ADS  Article  Google Scholar 

  20. 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 .

    ADS  Article  Google Scholar 

  21. 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. .

    Google Scholar 

  22. Vainio, R., Raukunen, O., Tylka, A.J., Dietrich, W.F., Afanasiev, A.: 2017, Why is solar cycle 24 an inefficient producer of high-energy particle events? Astron. Astrophys. 604, A47. DOI . ADS .

    ADS  Article  Google Scholar 

  23. 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 .

    ADS  Article  Google Scholar 

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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 ( ) and are grateful to the worldwide neutron-monitor database ( ), which is a product of an EU Project. We thank Marc Duldig, Erwin Flückiger, John Humble, and Roger Pyle for valuable discussions.

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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).

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  • Energetic particles