Forbush Effects and Geomagnetic Storms

Forbush effects in galactic cosmic rays (according to the neutron monitor network data) and accompanying geomagnetic disturbances over a long period from 1957 to 2022 have been identified and studied. Statistical relationships between various parameters of cosmic ray flux variations and geomagnetic activity indices are analyzed. It has been established that the magnitude of Forbush effects depends nonlinearly on the class of geomagnetic storm. A moderate correlation (up to 0.67) was found between the extreme values of various geomagnetic activity indices (Ap, Kp, Dst) and cosmic ray characteristics. It is shown that the extreme values of cosmic ray and geomagnetic activity parameters are not always detected simultaneously: it depends on the sign of the Bz-component of the interplanetary magnetic field in a specific event.