Characteristic association of geomagnetic storms and forbush decreases

Abstract

An attempt has been made to associate the characteristics of major geomagnetic storms and forbush decreases at 1 AU between 1999 and 2009. Most probable value for the Onset time difference is found between -1 to + 5 hours. It was also observed that majority of geomagnetic storms lag Forbush decreases only few geomagnetic storms lead Forbush decreases. 48.9% geomagnetic storms are found in the range of 0 to 10 hours, so that most probable value of main phase duration is 0 to 10 hours and recovery of geomagnetic storms are much faster than forbush decreases.