Ion acceleration and Alfvén wave generation at the Earth’s bow shock

Abstract

The processes of ion acceleration and Alfven wave generation by accelerated particles at the Earth’s bow shock are studied within a quasi-linear approach. Steady-state ion and wave spectra are shown to be established in a time of 0.3–4 h, depending on the background level of Alfvenic turbulence in the solar wind. The Alfven waves produced by accelerated ions are confined within the frequency range 10−2–1 Hz and their spectral peak with a wave amplitude βB ∼ B comparable to the interplanetary magnetic field strength B corresponds to the frequency v = (2–3) × 10−2 Hz. The high-frequency part of the wave spectrum (v > 0.2 Hz) undergoes damping by thermal ions. The calculated spectra of the accelerated ions and the Alfven waves generated by them reproduce the main features observed in experiments.