Astrophysics and Space Science

, Volume 74, Issue 2, pp 303–317

Cosmic-ray intensity related to solar and terrestrial activity indices in solar cycle No. 20

  • J. Xanthakis
  • H. Mavromichalaki
  • B. Petropoulos

DOI: 10.1007/BF00656441

Cite this article as:
Xanthakis, J., Mavromichalaki, H. & Petropoulos, B. Astrophys Space Sci (1981) 74: 303. doi:10.1007/BF00656441


The 11-year modulation of cosmic-ray intensity is studied using the data from nine world-wide neutron monitoring station over the period 1965–1975. From this analysis the following relation among the modulated cosmic-ray intensityI, the relative sunspot numberR, the number of proton eventsNp and the geomagnetic indexAp has been derived which describes the long-term modulation of cosmic rays
$$I = C - 10^{ - 3} (KR + 4N_P + 12A_P ),$$
whereC is a constant which depends on the rigidity of each station, andK is a coefficient related to the diffusion coefficient of cosmic rays and its transition in space. The standard deviation between the observed and calculated values of cosmic-ray intensity is about 5–9%. This relation has been explained by a generalization of the Simpson solar wind model which has been proved by the spherically symmetric diffusion-convection theory.

Copyright information

© D. Reidel Publishing Co. 1981

Authors and Affiliations

  • J. Xanthakis
    • 1
  • H. Mavromichalaki
    • 2
  • B. Petropoulos
    • 3
  1. 1.Research Centre for Astronomy and Applied MathematicsAcademy of AthensGreece
  2. 2.Nuclear Physics LaboratoryUniversity of AthensGreece
  3. 3.Research Centre for Astronomy and Applied MathematicsAcademy of AthensGreece