Forbush decrease in the intensity of cosmic rays in a toroidal model of a magnetic cloud

Abstract

The time dynamics of the particle distribution function in a magnetic cloud with the shape of a toroidal segment with the characteristic (forceless) structure of a magnetic field has been calculated. The shape of the cloud at the subsequent propagation in the interplanetary space has been determined by the kinematic model. The magnetic field of the cloud is calculated using the freezing-in condition. A significant effect of regions connecting the magnetic cloud with the Sun on the propagation of particles in the region of perturbation has been revealed. The calculation of the particle density and anisotropy of the intensity demonstrates reasonable agreement with the measurements. The results indicate the decisive role of the characteristic structure of the magnetic field in the time dynamics of the Forbush decrease in the intensity of cosmic rays.