Solar Physics

, 293:110 | Cite as

Effective Rigidity of a Polar Neutron Monitor for Recording Ground-Level Enhancements

  • Sergey A. Koldobskiy
  • Gennady A. Kovaltsov
  • Ilya G. UsoskinEmail author


The “effective” rigidity of a neutron monitor for a ground-level enhancement (GLE) event is defined so that the event-integrated fluence of solar energetic protons with rigidity above it is directly proportional to the integral intensity of the GLE as recorded by a polar neutron monitor, within a wide range of solar energetic-proton spectra. This provides a direct way to assess the integral fluence of a GLE event based solely on neutron-monitor data. The effective rigidity/energy was found to be 1.13 – 1.42 GV (550 – 800 MeV). A small model-dependent, systematic uncertainty in the value of the effective rigidity is caused by uncertainties in the low-energy range of the neutron-monitor yield function, which requires more detailed computations of the latter.


Cosmic rays Solar 



This work was partially supported by the ReSoLVE Centre of Excellence (Academy of Finland, project 272157). S.A. Koldobskiy acknowledges grant no. MK-6160.2018.2 of the President of the Russian Federation and MEPhI Academic Excellence Project (contract 02.a03.21.0005).

Disclosure of Potential Conflicts of Interest

The authors declare that they have no conflicts of interest.


  1. Adriani, O., Barbarino, G.C., Bazilevskaya, G.A., Bellotti, R., Boezio, M., Bogomolov, E.A., Bongi, M., Bonvicini, V., Bottai, S., Bruno, A., et al.: 2014, The PAMELA mission: heralding a new era in precision cosmic ray physics. Phys. Rep. 544, 323. DOI. ADS. ADSCrossRefGoogle Scholar
  2. Aguilar, M., Aisa, D., Alpat, B., Alvino, A., Ambrosi, G., Andeen, K., Arruda, L., Attig, N., Azzarello, P., Bachlechner, A., 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(17), 171103. DOI. ADS. ADSCrossRefGoogle Scholar
  3. Ahluwalia, H.S., Fikani, M.M.: 2007, Cosmic ray detector response to transient solar modulation: Forbush decreases. J. Geophys. Res. 112, A08105. DOI. ADS. ADSCrossRefGoogle Scholar
  4. Alanko, K., Usoskin, I.G., Mursula, K., Kovaltsov, G.A.: 2003, Heliospheric modulation strength: effective neutron monitor energy. Adv. Space Res. 32, 615. DOI. ADSCrossRefGoogle Scholar
  5. Asvestari, A., Willamo, T., Gil, A., Usoskin, I.G., Kovaltsov, G.A., Mikhailov, V.V., Mayorov, A.: 2017a, Analysis of ground level enhancements (GLE): extreme solar energetic particle events have hard spectra. Adv. Space Res. 60, 781. DOI. ADSCrossRefGoogle Scholar
  6. Asvestari, E., Gil, A., Kovaltsov, G.A., Usoskin, I.G.: 2017b, Neutron monitors and cosmogenic isotopes as cosmic ray energy-integration detectors: effective yield functions, effective energy, and its dependence on the local interstellar spectrum. J. Geophys. Res. 122, 9790. DOI. ADS. CrossRefGoogle Scholar
  7. Band, D., Matteson, J., Ford, L., Schaefer, B., Palmer, D., Teegarden, B., Cline, T., Briggs, M., Paciesas, W., Pendleton, G., Fishman, G., Kouveliotou, C., Meegan, C., Wilson, R., Lestrade, P.: 1993, BATSE observations of gamma-ray burst spectra. I – spectral diversity. Astrophys. J. 413, 281. DOI. ADS. ADSCrossRefGoogle Scholar
  8. Belov, A.: 2000, Large scale modulation: view from the Earth. Space Sci. Rev. 93, 79. DOI. ADS. ADSCrossRefGoogle Scholar
  9. Bieber, J.W., Clem, J., Evenson, P., Pyle, R., Sáiz, A., Ruffolo, D.: 2013, Giant ground level enhancement of relativistic solar protons on 2005 January 20. I. Spaceship Earth observations. Astrophys. J. 771, 92. DOI. ADS. ADSCrossRefGoogle Scholar
  10. Clem, J.M., Dorman, L.I.: 2000, Neutron monitor response functions. Space Sci. Rev. 93, 335. DOI. ADS. ADSCrossRefGoogle Scholar
  11. Cooke, D.J., Humble, J.E., Shea, M.A., Smart, D.F., Lund, N., Rasmussen, I.L., Byrnak, B., Goret, P., Petrou, N.: 1991, On cosmic-ray cut-off terminology. Nuovo Cimento C 14, 213. ADS. ADSCrossRefGoogle Scholar
  12. Dorman, L.I.: 2004, Cosmic Rays in the Earth’s Atmosphere and Underground, Kluwer, Dordrecht. CrossRefGoogle Scholar
  13. Gil, A., Usoskin, I.G., Kovaltsov, G.A., Mishev, A.L., Corti, C., Bindi, V.: 2015, Can we properly model the neutron monitor count rate? J. Geophys. Res. Space Phys. 120, 7172. DOI. ADS. ADSCrossRefGoogle Scholar
  14. Kovaltsov, G.A., Usoskin, I.G., Cliver, E.W., Dietrich, W.F., Tylka, A.J.: 2014, Fluence ordering of solar energetic proton events using cosmogenic radionuclide data. Solar Phys. 289, 4691. DOI. ADS. ADSCrossRefGoogle Scholar
  15. Mangeard, P.-S., Ruffolo, D., Sáiz, A., Nuntiyakul, W., Bieber, J.W., Clem, J., Evenson, P., Pyle, R., Duldig, M.L., Humble, J.E.: 2016a, Dependence of the neutron monitor count rate and time delay distribution on the rigidity spectrum of primary cosmic rays. J. Geophys. Res. Space Phys. 121, 11620. DOI. ADS. ADSCrossRefGoogle Scholar
  16. Mangeard, P.-S., Ruffolo, D., Sáiz, A., Madlee, S., Nutaro, T.: 2016b, Monte Carlo simulation of the neutron monitor yield function. J. Geophys. Res. Space Phys. 121, 7435. DOI. ADS. ADSCrossRefGoogle Scholar
  17. Mavromichalaki, H., Papaioannou, A., Plainaki, C., Sarlanis, C., Souvatzoglou, G., Gerontidou, M., Papailiou, M., Eroshenko, E., Belov, A., Yanke, V., Flückiger, E.O., Bütikofer, R., Parisi, M., Storini, M., Klein, K.-L., Fuller, N., Steigies, C.T., Rother, O.M., Heber, B., Wimmer-Schweingruber, R.F., Kudela, K., Strharsky, I., Langer, R., Usoskin, I., Ibragimov, A., Chilingaryan, A., Hovsepyan, G., Reymers, A., Yeghikyan, A., Kryakunova, O., Dryn, E., Nikolayevskiy, N., Dorman, L., Pustil’Nik, L.: 2011, Applications and usage of the real-time Neutron Monitor Database. Adv. Space Res. 47, 2210. DOI. ADS. ADSCrossRefGoogle Scholar
  18. Mishev, A.L., Usoskin, I.G., Kovaltsov, G.A.: 2013, Neutron monitor yield function: new improved computations. J. Geophys. Res. Space Phys. 118, 2783. DOI. ADS. ADSCrossRefGoogle Scholar
  19. Moraal, H., Caballero-Lopez, R.A.: 2014, The cosmic-ray ground-level enhancement of 1989 September 29. Astrophys. J. 790, 154. DOI. ADS. ADSCrossRefGoogle Scholar
  20. Raukunen, O., Vainio, R., Tylka, A.J., Dietrich, W.F., Jiggens, P., Heynderickx, D., Dierckxsens, M., Crosby, N., Ganse, U., Siipola, R.: 2018, Two solar proton fluence models based on ground level enhancement observations. J. Space Weather Space Clim. 8(27), A04. DOI. ADS. ADSCrossRefGoogle Scholar
  21. Shea, M.A., Smart, D.F.: 2000, Fifty years of cosmic radiation data. Space Sci. Rev. 93, 229. DOI. ADS. ADSCrossRefGoogle Scholar
  22. Shea, M.A., Smart, D.F.: 2012, Space weather and the ground-level solar proton events of the 23rd solar cycle. Space Sci. Rev. 171, 161. DOI. ADS. ADSCrossRefGoogle Scholar
  23. Simpson, J.A.: 2000, The cosmic ray nucleonic component: the invention and scientific uses of the neutron monitor – (keynote lecture). Space Sci. Rev. 93, 11. DOI. ADS. ADSCrossRefGoogle Scholar
  24. Tylka, A., Dietrich, W.: 2009, A new and comprehensive analysis of proton spectra in ground-level enhanced (GLE) solar particle events. In: 31th Internat. Cosmic Ray Conf., Universal Academy Press, Lodź, icrc0273 Google Scholar

Copyright information

© Springer Nature B.V. 2018

Authors and Affiliations

  1. 1.Space Climate Research UnitUniversity of OuluFinland
  2. 2.National Research Nuclear University MEPhIMoscowRussia
  3. 3.Ioffe Physical-Technical InstituteSt. PetersburgRussia
  4. 4.Sodankylä Geophysical ObservatoryUniversity of OuluFinland

Personalised recommendations