Abstract
We have studied geomagnetic storms ≤-50nT observed during the period of 1996-2008 with X-ray solar flares, magnetic clouds, interplanetary magnetic fields (IMF) and southward component of interplanetary magnetic fields (IMF Bz). We have determined 224 geomagnetic storms of defined criteria, out of which 198 (88.39%) are found to be associated with hard X-ray solar flare. The association rates of X-class, M-class, C-class, B-class, and A-class X-ray solar flares are 11.61%, 28.28%, 38.88%, 14.64%, and 6.56%, respectively, 133 out of 224 (59.38%) geomagnetic storms are associated with magnetic clouds (MC) of varying quality. The association rates for Excellent, Good, and Poor-quality magnetic clouds are 24.06%,58.64%, and 17.29%, respectively. Further all the geomagnetic storms are found to be associated with disturbances in interplanetary magnetic fields and a strong positive correlation with a correlation coefficient 0.79 has been found between magnitude of geomagnetic storms and maximum value of IMF disturbances. A large positive correlation with correlation coefficient 0.77 has been found between magnitude of geomagnetic storms and maximum value of IMF Bz disturbances during 1996-2008.
Keywords: – Geomagnetic storms, X-ray solar flare, Magnetic clouds, Interplanetary magnetic fields and Southward component of interplanetary magnetic fields.
Anita Shukla1, Laxmikant2*