Possibility of an Alfvenic Wave Resonator in the Magnetosphere

There has been recent activity in understanding the origin of high energy ($>$1 MeV) ``killer electrons'' in the Earth's magnetosphere. Previous work has identified the energization mechanism to be quasilinear diffusion involving whistler and ion-cyclotron waves\footnote{Mithaiwala, M.J. and W. Horton. JGR \textbf{110}. July 2005.}, which are generated by temperature anisotropy. It is known that whistler waves, through reflection at the lower-hybrid resonance, can form a resonator. We find that in a multi-ion species environment, such as the Earth's magnetosphere, the bi-ion rotation\footnote{Ganguli, G. and L. Rudakov. Phys. Plasmas \textbf{12}. April 2005.} (cutoff) frequency and Buchsbaum (resonance) frequency are important for the propagation and evolution of Alfvenic waves near the ion-cyclotron frequency. Here we show that Alfvenic waves with (k$_{\bot }>>$ k$_{z})$ can be captured by a magnetic cavity to form a strongly localized Magnetospheric Resonator which can interact with the electrons over a long time period and can lead to both energization and loss of the electrons. The Alfvenic waves can be generated by a ring distribution of one of the ion species. Ring ion distributions are known to form when the solar wind interacts with the magnetosphere or a comet interacts with the solar wind, and by the release of chemicals in the magnetosphere.