Аңдатпа
The behavior of the galactic cosmic ray density and vector anisotropy during geomagnetic storms with sudden storm commencements has been investigated based on the global survey data. It is shown that the average anisotropy significantly increases directly before a sudden storm commencement; the larger the subsequent Forbush decrease, the larger the increase in anisotropy. The averaged values of the CR anisotropy and density start to be affected by the shock wave approximately 5 h before its arrival. Changes in the anisotropy direction (especially for west Forbush sources) can be observed much earlier.