Damping and transformation of fast magnetoacoustic waves in the case of resonance at the ion cyclotron frequency harmonic in a plasma in a nonuniform magnetic field

A theoretical analysis is presented of the propagation of fast magnetoacoustic waves in a straight nonuniform magnetic field through a resonant plasma layer, where the wave frequency is equal to twice the ion cyclotron frequency. The propagation and damping of these waves, and their transformation into electrostatic ion cyclotron waves is considered in the local approximation for a layer with a slowly changing magnetic field. An equation is obtained for the behavior of the field of the wave in the resonant layer with a sharply changing magnetic field in the case when the local approximation is not applicable. It is noted that such nonlocal effects can be significant for tokamaks.