A Wavelet Analysis of Geomagnetic Storms During 1957-2008

Abstract

Large amount of energetic particles reach the magnetosphere of earth when solar wind is intensified by solar events such as coronal mass ejection and solar flares. The solar wind-magnetosphere coupling due to this intensified solar wind results in intense and irregular geomagnetic disturbances called geomagnetic storms. A detailed periodicity study of geomagnetic storms helps us to create a database leading to the space weather modeling and prediction. In this study, Dst index derived through global processing and averaging of all H-components of various observatories is used to identify geomagnetic storms. A time series signal of the occurrence of geomagnetic storms using Dst is synthesized for the period under study. The detailed information on the time localization of each frequency component of the occurrence of geomagnetic storms is revealed by the wavelet transform of this time series. The temporal evolution and the mean strength of periodicities are revealed from the Continuous Wavelet Power Spectrum (CWPS) and Global Wavelet Spectrum (GWS) of the data. Geomagnetic storms are shown to exhibit semiannual, annual, biennial, triennial and 11 year periodicities, of which the most prominent periodicity is of 10-11 years.

Keywords: Geomagnetic Storms, periodicity, wavelet transform