Nonconvective ion cyclotron instability

The electromagnetic ion cyclotron instability is shown to be nonconvective for a wide range of plasma β's and ring current proton anisotropies A. The addition of cold plasma to the ring current enlarges the region of the β-A parameter space for nonconvective instability. Thus, despite the high Alfvén speed outside the plasmasphere, ion cyclotron wave amplitudes could grow to appreciable levels and contribute to the pitch-angle and energy diffusion of ring current protons.