In the work variations of density, vector and tensor anisotropies of cosmic rays in the periods of Forbush decreases are investigated. The information about angular distribution of cosmic rays is obtained on the basis of the data of world-wide network of neutron monitors using the global survey method. Abrupt amplitude-phase oscillations of cosmic ray anisotropy during forbush decreases of unknown origin are found. In order to explain the obtained results the model of magnetic mirror is proposed. The model is based on kinetic consideration of the modulation process and allows to count the first two spherical harmonics of cosmic ray angular distribution. A comparison of the model calculations and the experimental data is carried out