Forbush decrease of the galactic cosmic ray intensity: experimental study and theoretical modeling

摘要

We study the temporal changes of the power law rigidity spectrum of the Forbush decrease (Fd) of the galactic cosmic ray (GCR) intensity. We show that the power law rigidity spectrum of Fd for the period of 6–20 November 2004 found by neutron monitors and ground muon telescopes experimental data, gradually is hardening during the decreasing phase of the intensities and then steadily is softening during the recovery phase. A relation of the rigidity spectrum exponent of the Fd of the GCR intensity with the exponent of the power spectral density (PSD) of the components of the interplanetary magnetic field (IMF) turbulence is established. We develop three dimensional (3-D) non stationary model of the Fd and show that the results of the theoretical modeling are in good agreement with the experimental data. We suppose that temporal changes of the rigidity spectrum exponent of the Fd of GCR intensity can be used to calculate the exponent of the PSD of the IMF turbulence for the arbitrary period, which is not achievable by the in situ measurements of the IMF.