Relaxation Processes in Plasmas with Magnetic Field. Temperature Relaxations

Abstract

The Fokker‐Planck coefficients of a plasma in the magnetic field are calculated in terms of the spectral function of the electric‐field fluctuations and the dielectric response function; the results are used for the investigation of temperature relaxation processes. It is found that the relaxation rate between the electron and ion temperatures contains, in addition to the usual Spitzer rate, an anomalous term which diverges logarithmically as the mass ratio approaches zero. The physical origin of this anomalous term is the strong coupling between the spiral motion of the electrons and the long‐wavelength, low‐frequency fluctuations produced by the ions; its magnitude can become comparable to the Spitzer rate for a strong magnetic field. In the case of the temperature relaxation between the parallel and perpendicular directions to the magnetic field, the screened Coulomb interaction provides the major relaxation mechanism; the effects of the fluctuations associated with the Bernstein modes are negligibly small.