A general approach to the description of the fluctuations of the electric and magnetic fields in a plasma placed in a strong external magnetic field is developed. The wave dispersion is considered and the dependences of the damping rates of the Alfvén and magnetosonic waves on the propagation angle and parameters of the plasma are analysed. The spectral distributions of the fluctuations of the electric and magnetic fields in the frequency ranges and of the spectrum for the plasma with strong external magnetic field are studied in detail. The spectral distributions of the fluctuations of the electric and magnetic fields in non-equilibrium plasmas are treated. Effective temperatures have been introduced both for the collective Alfvén and magnetosonic fluctuations and for the incoherent fluctuations in low-frequency range; they can be used as convenient parameters for the description of the non-equilibrium state of plasmas in diagnostics in facilities devised for realization of the controlled thermonuclear fusion.
Evaluation of local magnetic field fluctuation in a toroidal plasma with heavy ion beam probe