On the Occurrence of Geomagnetic Storms with Sudden Commencements

抄録

Geomagnetic storms with sudden commencement happened from June 1957 to December 1980 are considered. The characteristic size of the storm intensity is assumed to be represented by the absolute value of D_st index in a time scale of seven months. As this magnitude is bounded in maximum size, Gumbel's third extreme value distribution is applied to predict the occurrence of storms. According to that, modal extreme values and return periods are estimated. Events with modal extremes values of 400 nT are predicted to happen within the next (17 ± 3) years since 1980.