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

The electron kinetic response to an electric current driven by a standing shear Alfven wave (SAW) is considered for the case of a dipolar geometry. The parallel electric field is found from the electron gyrokinetic equation along 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 used by many authors significantly underestimate the electron response and, consequently, the magnitude and location of the parallel electric field under conditions where the electron bounce frequency is larger than the SAW frequency. This is especially important in a plasma with density depressions near the Earth's polar magnetosphere. (C) 2000 American Institute of Physics. [S1070-664X(00)02004-8].