Causes responsible for intense and severe storms during the declining phase of Solar Cycle 24

The occurrence of total 113 geomagnetic storms during declining phase of Solar Cycle 24 (2015-2017) subdivided as about 105 moderate storms (Dst=-50nT to -100 nT), 6 intense storms (Dst=-100nT to -200 nT) and 2 severe storms (Dst<-200nT) has been diagnosed on the basis of 5 day active window through the CACTus (Computer aided CME tracking) software. A detailed study has been carried out for the 6 intense and 2 severe storms. It is inferred that CMEs are the major source of geomagnetic storms to occur. Out of the 6 intense and 2 severe storms, only 1 has been observed with the origin of CIR. Thus, all analyzed intense geomagnetic storms are due to coronal mass ejection at the Sun. Most of our results are in good accordance with other reported results.