Electrostatic Instabilities and Electron Heating in Magnetized Plasmas Driven by a Strong Electric Field Oscillating Near the Lower Hybrid Frequency.
The heating of a magnetized plasma due to instabilities driven by an electric field oscillating near the lower hybrid frequency is studied analytically and through computer simulations. The linear theory is investigated emphasizing the effects of a large amplitude pump and propagation angles far from resonance with the driver frequency. The combination of these two conditions leads to new unstable modes. These modes possess large growth rates and are characterized by large parallel wavenumbers. One dimensional particle simulations show that these modes can efficiently heat low energy electrons. The electron heating rate observed in these simulations is comparable to that observed in experiments and in two dimensional simulations; therefore these off resonant modes are important and cannot be neglected. The discrepancy between two dimensional simulations which showed tail electron heating and the experimental observation of bulk electron heating is discussed. It is shown that the electron heating is due to quasi-linear diffusion. We also calculate the heating due to absorption of the pump wave on an ion acoustic wave; this is relevant because of the possibility of isotropic ion acoustic turbulence due to non-linear ion Landau damping. Finally, future directions for studying this problem are discussed.
- Pub Date:
- Physics: Fluid and Plasma