Ion-streaming instabilities: Electromagnetic and electrostatic

Electromagnetic effects are shown to reduce the threshold velocity (relative to electrostatic calculation) for ion-beam instabilities in plasmas where the beam velocity, taken parallel to the magnetic field, becomes a modest fraction of the Alfvén velocity. The most unstable mode occurs for frequencies in the ion-cyclotron frequency range and is caused by an interaction of the beam with a type of electromagnetic ion-cyclotron wave. Applications of the theory range from basic research experiments, to collisionless shocks and two-component thermonuclear burning devices.