Occurrence rate of extreme magnetic storms

We investigate the occurrence rate of magnetic storms at the Earth. During the first part of our study, the standard and integral distribution functions of magnetic storm value (minimal Dst index) for the period 1963-2012 are analyzed and results show that the standard and integral distribution functions have power law tails with indexes =-4.4 and -3.4, respectively. During the second part, statistical analysis of occurrence rate of magnetic storms induced by different types of interplanetary drivers is made using OMNI data for the period 1976-2000. Using our catalog of large-scale types of solar wind streams, we study storms induced by interplanetary coronal mass ejections (ICMEs) (separately magnetic clouds (MCs) and Ejecta) and both types of compressed regions: corotating interaction regions (CIRs) and Sheaths. For these types of drivers, we calculate the integral probabilities of storms with minimum Dst -50, -70, -100, -150, and -200 nT. The highest probability in this interval of Dst is observed for MCs, with the probabilities for other drivers being 3-10 times lower. Extrapolation of these results to extreme storms shows that a magnetic storm as large as the Carrington storm in 1859 with Dst=-1760 nT is observed on the Earth with frequency not higher than one event during approximate to 500 years.