NUMERICAL STUDY OF THE UPSTREAM WAVE EXCITATION MECHANISM. 1. NONLINEAR PHASE BUNCHING OF BEAM IONS.

Abstract

By means of particle simulation, the excitation mechanism of low-frequency (0. 01-0. 05 Hz) upstream hydromagnetic waves is studied. Initially, excitation of the right-hand polarized waves propagating parallel to the field-aligned ion beam, which is given as the free energy source was used. In the nonlinear stage, the phase space bunching of beam ions by the excited waves was observed. This bunching effect is applied to explain the 'gyrophased bunched' ions observed in the foreshock region.