On the effect of trapped particles in the regime of cyclotron resonance

The motion of particles in a finite amplitude wave, propagating obliquely to the homogeneous magnetostatic field is discussed. As follows from simple integral properties, in the neighbourhood of Doppler-shifted cyclotron resonance similar trapping effects appear as in a plasma without magnetostatic field. Consequences of this trapping are discussed, in particular, the possibility of a strong absorption of the wave, and the origin of stochastic instabilities caused by the perturbation of an effective trapping potential and leading to the acceleration of particles.The author is indebted to Dr. R.Klíma, Dr. J.Lacina and Dr. P.unka for interesting discussions and to Dr. .Körbel, Mrs. P.Jaroová and Mrs. A.Harmáková for numerical calculations.