Statistics of Extreme Time-Integrated Geomagnetic Activity

A statistical analysis of the time-integrated Dst index is performed over 1958-2007. The tail of the probability distribution of extreme time-integrated Dst events, which occur during strong geomagnetic storms, can be precisely fitted by a power law function with upper cutoff, apparently not exceeded even by the 1859 Carrington event. This time-integrated Dst is expected to be a reasonable proxy for maximum densities of MeV electrons in the heart of the outer radiation belt, which are known to pose a serious threat to satellites. During such strong events, a correlation is found between the time-integrated levels of various physical quantities, such as interplanetary magnetic field B-z, particle energy fluxes measured during injections in the magnetotail, geosynchronous ULF wave index, and geomagnetic activity in the inner magnetosphere, suggesting cumulative effects from successive disturbances.