Modeling and Experimental Study of the Forbush Effect of Galactic Cosmic Rays

We study the sporadic Forbush effects of the galactic cosmic ray intensity using neutron monitors and muon telescopes experimental data and the theoretical modeling developed based on the Parker’s transport equation for a non stationary case. We found that a hard rigidity spectrum in the minimum phase of the Forbush effects of GCR intensity determined by neutron monitors experimental data is related with the enhancement of the power spectral density in the energy range of the interplanetary magnetic field turbulence. It is shown that the increase of the exponent of the power spectral density in the low frequency region of the energy range of the interplanetary magnetic field turbulence leads to the hard rigidity spectrum of the galactic cosmic ray intensity during the main phase of the Forbush effect. The experimental results are confirmed by the modeling based on the assumption that there exists the power law dependence of the diffusion coefficient on the rigidity of the GCR particles; owing to this dependence there should be the reversal relationship between the exponent of the power law rigidity spectrum of the of Forbush effect of GCR intensity and the exponent of the power spectral density in the energy range of the interplanetary magnetic field turbulence.