Electron kinetic effects in standing shear Alfven waves in the dipolar magnetosphere

The electron kinetic response to an electric current driven by a standing s hear Alfven wave (SAW) is considered for the case of a dipolar geometry. Th e parallel electric field is found from the electron gyrokinetic equation a long with the SAW dispersion coefficient. Electron trapping in the dipolar magnetic field significantly reduces the parallel electric conductivity and in this way increases the amplitude of the parallel electric field and SAW dispersion. It is demonstrated that the two-fluid hydrodynamic equations u sed by many authors significantly underestimate the electron response and, consequently, the magnitude and location of the parallel electric field und er conditions where the electron bounce frequency is larger than the SAW fr equency. This is especially important in a plasma with density depressions near the Earth's polar magnetosphere. (C) 2000 American Institute of Physic s. [S1070-664X(00)02004-8].