On the temperature dependence of the wave cut-off

Abstract

For arbitrary wave propagation angle with respect to the magnetic field the wave cutoff and in particular, its dependence on the particle temperature are investigated. The obtained results demonstrate that when the wave propagation near the true cut-off (N-perpendicular to = N-parallel to = 0) as well as the cut-off of waves propagating at fixed, real N-parallel to-value (N-perpendicular to = 0, N-parallel to not equal 0) are considered, it is essential to take relativistic effects into account. A simple expression is given for the cut-off density which is acceptable for most applications below T = 20 keV. In this temperature range it predicts values of the cut-off density of the ordinary mode which are close to the relativistic ones.