Effects of auroral potential drops on plasma sheet dynamics

This extra load reduces the field-aligned current (j(parallel to)) supplied by nightside reconnection dynamos. The system adapts by forcing the nightside X line closer to Earth, with a corresponding reduction in current lensing (j(parallel to)/B = constant) at the ionosphere and additional contraction of the plasma sheet during substorm recovery and steady magnetospheric convection.

For steady and moderate solar wind driving and with constant ionospheric conductance, the cross polar cap potential and hemispheric field-aligned current are lower by approximately the ratio of the peak field-aligned potential drop to the cross polar cap potential (10-15%) when potential drops are included. Hemispheric ionospheric Joule dissipation is less by 8%, while the area-integrated, average work done on the fluid by the reconnecting magnetotail field increases by 50% within vertical bar y vertical bar< 8 RE.