Tail current sheet dynamics during substorm

A model of the tail current sheet is presented. This model describes the cross-tail current and closure currents on the magnetopause. The cross-tail current sheet with changing thickness is considered. The dependence of the B-z-component of the total magnetospheric field on the tail current strength is calculated. The IMF B-z-component during southward IMF interval causes thinning of the tail current sheet and an increase of the cross-tail current. As a consequence of this process, the B-z-component of the total magnetospheric field normal to the current sheet decreases, the equilibrium conditions are violated, and a substorm occurs.