When the interplanetary magnetic field turns southward, dayside reconnection leads to an increase of open-magnetic flux and an increase of the electric potential drop across the polar cap. The enhanced electrostatic field in the ionosphere can be-mapped to the closed field region of magnetotail, contributing to a dawn-to-dusk electrostatic component of electric field in the plasma sheet. In the presence of this driving electric field, an adiabatic evolution of the plasma sheet is formulated in A-space, where A is the magnetic flux function. It is found that the adiabatic evolution leads to the observed enhancement of the entropy content in the near-earth plasma sheet and to a tailward stretching of geomagnetic field lines. As a result, the cross-tail current in the near-earth plasma sheet is strongly enhanced. ¿ American Geophysical Union 1995