Advertisement

Solar Physics

, Volume 262, Issue 1, pp 199–212 | Cite as

Modulation Cycles of Galactic Cosmic Ray Diurnal Anisotropy Variation

  • S. Y. Oh
  • Y. YiEmail author
  • J. W. Bieber
Article

Abstract

The diurnal variation of the galactic cosmic ray (GCR) count rates measured by a ground-based neutron monitor (NM) station represents an anisotropic flow of GCR at 1 AU. The variation of the local time of GCR maximum intensity (we call the phase) is thought in general to have a period of two sunspot cycles (22 years). However, other interpretations are also possible. In order to determine the cyclic behavior of GCR anisotropic variation more precisely, we have carried out a statistical study on the diurnal variation of the phase. We examined 54-year data of Huancayo (Haleakala), 40-year data from Rome, and 43-year data from Oulu NM stations using the ‘pile-up’ method and the F-test. We found that the phase variation has two components: of 22-year and 11-year cycles. All NM stations show mainly the 22-year phase variation controlled by the drift effect due to solar polar magnetic field reversal, regardless of their latitudinal location (cut-off rigidity). However, the lower the NM station latitude is (the higher the cut-off rigidity is), the higher is the contribution from the 11-year phase variation controlled by the diffusion effect due to the change in strength of the interplanetary magnetic fields associated with the sunspot cycle.

Keywords

Galactic cosmic rays Diurnal variation Modulation cycle Solar cyclic variation 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Agrawal, S.P.: 1983, Space Sci. Rev. 34, 127. CrossRefADSGoogle Scholar
  2. Ahluwalia, H.S.: 1988, Geophys. Res. Lett. 15, 287. CrossRefADSGoogle Scholar
  3. Bieber, J.W., Chen, J.: 1991, Astrophys. J. 372, 301. CrossRefADSGoogle Scholar
  4. Bieber, J.W., Pomerantz, M.A.: 1983, Geophys. Res. Lett. 10, 920. CrossRefADSGoogle Scholar
  5. Bieber, J.W., Pomerantz, M.A.: 1986, Astrophys. J. 303, 843. CrossRefADSGoogle Scholar
  6. Bieber, J.W., Evenson, P.A., Matthaeus, W.H.: 1987, Geophys. Res. Lett. 14, 864. CrossRefADSGoogle Scholar
  7. Duggal, S.P., Forbush, S.E., Pomerantz, M.A.: 1970a, Acta Phys. Acad. Sci. Hung. 29(Suppl. 2), 55. Google Scholar
  8. Duggal, S.P., Forbush, S.E., Pomerantz, M.A.: 1970b, J. Geophys. Res. 75, 1150. CrossRefADSGoogle Scholar
  9. Duldig, M.L.: 2001, Publ. Astron. Soc. Aust. 18, 12. CrossRefADSGoogle Scholar
  10. Fenton, A.G., Humble, J.E., Thambyahpillai, T.: 1983, In: Durgaprasad, N., et al. (eds.) Proc. 18th Int. Cosmic Ray Conf. 10, 186. Google Scholar
  11. Fillius, W., Axford, W.I., Wood, D.: 1985, In: Jones, F.C., Adams, J., Mason, G.M. (eds.) Proc. 19th Int. Cosmic Ray Conf. 5, 189. Google Scholar
  12. Fonger, W.H.: 1953, Phys. Rev. 91, 351. CrossRefADSGoogle Scholar
  13. Forbush, S.E.: 1937, Terr. Magn. Atmos. Electr. 42, 1. CrossRefGoogle Scholar
  14. Forbush, S.E.: 1967, J. Geophys. Res. 72, 4937. CrossRefADSGoogle Scholar
  15. Forbush, S.E.: 1969, J. Geophys. Res. 74, 3451. CrossRefADSGoogle Scholar
  16. Forbush, S.E.: 1981, In: Auger, P., et al. (eds.) Proc. 17th Int. Cosmic Ray Conf. 10, 209. Google Scholar
  17. Kadokura, A., Nishida, A.: 1986, J. Geophys. Res. 91, 1. CrossRefADSGoogle Scholar
  18. Lopate, C., McKibben, R.B., Pyle, K.R., Simpson, J.A.: 1990, In: Protheroe, R.J. (ed.) Proc. 21th Int. Cosmic Ray Conf. 6, 128. Google Scholar
  19. McDonald, F.B., von Rosenvinge, T.T., Lal, N., Schuster, P., Trainor, J.H., Van Hollebeke, M.A.I.: 1985, In: Jones, F.C., Adams, J., Mason, G.M. (eds.) Proc. 19th Int. Cosmic Ray Conf. 5, 193. Google Scholar
  20. Minnie, J., Bieber, J.W., Matthaeus, W.H., Burger, R.A.: 2007, Astrophys. J. 670, 1149. CrossRefADSGoogle Scholar
  21. Moraal, H., Caballero-Lopez, R.A., McCracken, K.G., Humble, J.E.: 2005, Astrophys. J. 629, 556. CrossRefADSGoogle Scholar
  22. Oh, S.Y., Yi, Y., Kim, Y.H.: 2008, J. Geophys. Res. 113, A01103. CrossRefGoogle Scholar
  23. Oh, S.Y., Yi, Y.: 2009, J. Geophys. Res. 114, A11102. CrossRefGoogle Scholar
  24. Pandey, G.K., Tiwari, C.M., Shrivastava, P.K.: 2005, In: Acharya, B.S., et al. (eds.) Proc. 29th Int. Cosmic Ray Conf. 2, 167. Google Scholar
  25. Potgieter, S.M., Burger, A.R.: 1990, In: Protheroe, R.J. (ed.) Proc. 21th Int. Cosmic Ray Conf. 6, 83. Google Scholar
  26. Singh, M., Badruddin: 2006, Solar Phys. 233, 291. CrossRefADSGoogle Scholar
  27. Thambyahpillai, T., Elliot, H.: 1953, Nature 171, 918. CrossRefADSGoogle Scholar
  28. Tiwari, C.M., Agrawal, S.P.: 2005, In: Acharya, B.S., et al. (eds.) Proc. 29th Int. Cosmic Ray Conf. 2, 187. Google Scholar
  29. Tiwari, C.M., Tiwari, D.P., Shrivastava, P.K.: 2005, Curr. Sci. 88, 1275. Google Scholar

Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  1. 1.Bartol Research Institute, Department of Physics and AstronomyUniversity of DelawareNewarkUSA
  2. 2.Department of Astronomy and Space ScienceChungnam National UniversityDaejeonKorea

Personalised recommendations