Solar cycle distribution of great geomagnetic storms

The distribution properties of great geomagnetic storms (Dst≤−200 nT) and super geomagnetic storms (Dst≤−300 nT) across the solar cycles (19–23) are investigated. The results show that 73.2% of the great geomagnetic storms took place in the descending phase of the solar cycles. 72.7% of super geomagnetic storms occurred in the descending phase of the solar cycles. About 83% of the great geomagnetic storms appeared during the period from the two years before solar cycle peak and the three years after solar cycle peak time. 90.9% of the super geomagnetic storms appeared between the two years before solar cycle peak and the three years after solar cycle peak. When a solar cycle is very strong, the phenomenon that great geomagnetic storms concentrated during the period from the two years before the solar cycle peak time to the three years after the solar cycle peak time is very prominent. The launch time of space science satellite is suggested according to the distribution properties of great geomagnetic storms and super geomagnetic storms in solar cycles.