Characteristics of Wave--Particle Interaction in a Hydrogen Plasma

We study the characteristics of cyclotron wave--particle interaction in a typical hydrogen plasma. The numerical calculations of minimum resonant energy E_min, resonant wave frequency ω, and pitch angle diffusion coefficient D_αα for interactions between R-mode/L-mode and electrons/protons are presented. It is found that E_min decreases with ω for R-mode/electron, L-mode/proton and L-mode/electron interactions, but increase with ω for R-mode/proton interaction. It is shown that both R-mode and L-mode waves can efficiently scatter energetic (10keV~100keV) electrons and protons and cause precipitation loss at L=4, indicating that perhaps wave--particle interaction is a serious candidate for the ring current decay.