The relation between solar activity and orientation of the solar wind electric field relative to the Earth's magnetic moment

The relation of the Kp index of geomagnetic activity to the solar wind electric field (E (SW)) and the projection of this field onto the geomagnetic dipole has been estimated. An analysis indicated that the southward component of the IMF vector (B (z) < 0) is the main geoeffective parameter, as was repeatedly indicated by many researchers. The presence of this component in any combinations of the interplanetary medium parameters is responsible for a high correlation between such combinations and geomagnetic activity referred to by the authors of different studies. Precisely this field component also plays the main role in the relation between the Kp index and the relative orientation of E (SW) and the Earth' magnetic moment.