CRITICAL WAVE SPECTRA FOR STOCHASTIC HEATING OF A MAGNETIZED PLASMA

Stochasticity of particles in a magnetized plasma as a result of many waves with common frequency ω and different wave vectors k is examined. A critical potential amplitude Φc(k) = ∈c/k ∥4 is verified with the following property: Effective heating along the magnetic field B0 by small-amplitude waves is only possible in the velocity interval (ω/kmax)≤v∥ ≤(ω/kmin), where kmin, kmax denote the interval for k∥ (parallel to B0) in which |Φ(k)|≥|Φc(k)|. Heating perpendicular to B0 by circularly polarized waves with a Fourier spectrum peaked around a perpendicular wave vector k⊥ is strongly inhibited by the presence of an adiabatic invariant, but these barriers can be overcome by waves with a sufficiently broad spectrum in k⊥. © 1990 American Institute of Physics.