Reactive instabilities of lower hybrid-like waves in regions with parallel currents

Abstract

The dispersion and reactive instabilities of obliquely propagating waves near the lower hybrid (LH) frequency are studied in plasma carrying a current parallel to the magnetic field. Possible applications of these instabilities include magnetic reconnection regions, where LH-like waves may accelerate and heat both ions and electrons. In plasmas with a bulk drift of electrons relative to the ions at speed vd along the magnetic field, the forward and backward propagating LH modes are shown to be replaced by four LH-like modes. Reactive instabilities are discovered here for a forward propagating mode with Re(ω)≈k∥vd/2 and a backward propagating mode with Re(ω) <~5Ωi. Numerical warm, fully electromagnetic, kinetic calculations are compared with cold plasma calculations and agree well, confirming that the discovered instabilities are reactive. In the cold plasma limit, the forward and backward propagating instabilities occur for vd below and above some thresholds, respectively.