Oscillating two-stream and parametric decay instabilities in a weakly magnetized plasma

Abstract

The paper considers the effects of a weak ambient magnetic field on the oscillating two-stream and parametric decay instabilities with emphasis on the dependence of the angular variation of the instability thresholds and growth rates on the magnetic field. A dispersion relation is derived in the limit in which the electron plasma frequency is much greater than the cyclotron frequency, and is solved for dipole and monochromatic pump spectra. The analysis shows that the presence of a magnetic field can substantially enhance thresholds and reduce growth rates for waves propagating at an oblique angle with respect to the ambient magnetic field, so that the magnetic field has a stabilizing influence on the off-parallel propagating modes.