PONDEROMOTIVE WAVE-FORCES IN LONGITUDINAL MHD WAVE-GUIDES

By using a general expression for the ponderomotive wave force, we hav e evaluated the action of ion cyclotron Alfven waves on the plasma den sity in a longitudinal waveguide. The main effect is the condensation of the plasma in the vicinity of the waveguide equator. According to o bservations onboard the GEOS 1 and Viking satellites, the amplitudes o f such geomagnetic pulsations can reach up to several nanoteslas. This is sufficient to cause a strong modification of the cold plasma densi ty in the magnetosphere under the action of ion cyclotron Alfven pulsa tions. Furthermore, we have also speculated on the possible effects of the ponderomotive wave force on the problems connected with the so ca lled ''wave-induced substorms'' in the neutral sheet of the geomagneti c tail as well as with the phenomenon of ''ponderomotive plasma fillin g,'' which determines the relaxation of the plasmasphere after the geo magnetic perturbations.