Modifications of the magnetospheric plasma due to ponderomotive forces

By means of two simple examples it is demonstrated that the ponderomotive force induced by the geomagnetic pulsations significantly modifies the plasma distribution in the Earth's magnetosphere. The first example considers the quasi-static plasma equilibrium at closed magnetic shells. Ponderomotive forces, averaged over the geomagnetic pulsation period, increase the plasma density at the equator of the oscillating magnetic shell. If the oscillation amplitude exceeds a certain critical level, the quasi-static solution predicts a maximum of the plasma density at the equator of the magnetic shell. The second example considers the quasi-stationary plasma flow along the open field lines stretching into the geomagnetic tail (the polar wind). The inclusion of the ponderomotive force may shift the critical point for the flow transition through the supersonic barrier closer to the Earth.