Influence of wave frequency variation on anomalous cyclotron resonance interaction of energetic electrons with finite amplitutude ducted whistler-mode wave

Abstract

The influence of wave frequency variation on the anomalous cyclotron resonance $\omega=\omega_{Be}+kv_{\|}$ interaction (ACRI) of energetic electrons with a ducted finite amplitude whistler-mode wave propagating through the so-called transient plasma layer (TPL) in the magnetosphere or in the ionosphere is studied both analytically and numerically. The anomalous cyclotron resonance interaction takes place in the case when the whistler-mode wave amplitude $B_{W}$ is consistent with the gradient of magnetic field $\overrightarrow{B_0}$. The region of phase space occupied by anomalously interacting energetic electrons (synchronous particles) is determined. The efficiencies of both the pitch-angle scattering of resonant electrons and their transverse acceleration are studied and the efficiencies dependence on the magnitude and sign of the wave frequency drift is considered. It has been shown that in the case of ACRI occuring under conditions relevant to VLF-emission in the magnetosphere, the energy and pitch-angle changes of synchronous electrons may be enchanced by a factor $10^2 \div 10^3$ in comparison with ones for nonsynchronous resonant electrons. So the small in density group of synchronous particles may give significant contribution to a whistler-mode wave damping in TPL.