Contribution of geometry of interaction between interplanetary and terrestrial magnetic fields into geomagnetic activity

Abstract

We present results of our study of dependence of planetary geomagnetic activity from geometric factors in geoeffective parameters taking into account orientation of the geomagnetic moment M relative to the vectors of the Interplanetary Magnetic Field (IMF) and electric field of the solar wind E during annual and daily motions of the Earth. We take as our data base space measurements of the IMF and solar wind velocity at the Earth's orbit for 1964-1998 and Kp, Dst indices. Variations of the geometric factors determined by mutual orientation of the vectors E and M can explain 50% of observed variations of Kp and 75% of Dst. We show that geomagnetic activity can reach very high levels of geomagnetic activity Kp = 8 for invariable values of the solar wind electric field by changing only geometric factors.