... Geomagnetic activity can be divided into two main categories, storms and substorms . Storms, the main contributors to space weather , are initiated when enhanced energy transfer from the solar wind/IMF into the magnetosphere leads into intensification of ring current . The ring current development can be monitored with the Dst index . ... Iyemori, T., and D. R. K. Rao, Decay of the Dst field of geomagnetic disturbances after substorm onset and its implication to storm-substorm relation, Ann. ...