FIELD-ALIGNED CURRENT GENERATION FROM MHD WAVES IN THE TERRESTRIAL MAGNETOSPHERE

It is shown by the quasilinear Fokker-Planck approach that MHD, lower hybrid, whistler, electron-cyclotron and ion-cyclotron waves present in the magnetosphere can generate a noninductive DC current, aligned with the ambient magnetic field. The efficiency of current generation is determined for waves damped via Cherenkov (Landau and TTMP) damping. As a specific application, the current generation by the kinetic shear Alfven wave is considered for plasmapause electrons. The efficiency obtained is eta congruent-to 1(muA m-2)(mu Wm-2) and the wave-power dissipation necessary to generate currents at the Birkeland current level (J congruent-to 10(-4) A m-2) is P(d) congruent-to 100 muW m-2. Finally, it is also shown that the ideal (MHD) shear Alfven wave cannot generate a DC field-aligned current via Cherenkov damping, since E(parallel-to) = 0 and B(parallel-to) = 0, where E(parallel-to) and B(parallel-to) are the field-aligned wave electric and magnetic fields, respectively.