Oscillating two-stream instability of ion cyclotron waves

Abstract

It is shown that a high power electrostatic pump around ion cyclotron frequency is unstable for a purely growing short wavelength (k≫k0) perturbation, viz., oscillating two-stream instability. For typical PLT parameters, the instability is excited when the electric field amplitude E0 exceeds 0.2 esu (i.e., the power ≳200 kW). When the pump is a Bernstein eigenmode (ω0≲ωci, k0zve<ω0), the instability occurs over a wide range of k values and the growth rate is large (of the order of 10−4 sec−1). For ω0≳ωci, the instability has a large growth rate only when the frequency shift is large, i.e., the pump is not an eigenmode. In the case of an ion cyclotron eigenmode, the instability occurs only for restricted k values and pump powers.