Field-aligned current generation from MHD waves in the terrestrial magnetosphere

Abstract

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 Alfvén wave is considered for plasma- pause electrons. The efficiency obtained is η ⋍ 1(μ A m −2)(μ W m −2) and the wave-power dissipation necess- ary to generate currents at the Birkeland current level ( J ∥ − 10 ⋍4 A m −2 ) is P d ⋍ 100 μW m −2 . Finally, it is also shown that the ideal (MHD) shear Alfven wave cannot generate a DC field-aligned current via Cher- enkov damping, since E ∥ = 0 and B ∥ = 0, where E ∥ and B ∥ are the field-aligned wave electric and magnetic fields, respectively.