Direct-driven mechanism for geomagnetic storms

We have obtained the injection function for the part of the storm-time depression which is related tb the cross-tail current and corresponding currents on the magnetopause. This injection function is Q(TC) =-kappa U/S where U is the electric potential difference between the dawn and dusk sides of the magnetosphere, S is the equatorial cross-section of the stable trapping region, and kappa is a coefficient varying from 0.5 to 1.5 depending on the state of the magnetosphere and solar wind pressure. The injection function Q(TC) appeared to be close to the observed one for the Dst-variation.