The author formulates the conditions under which cyclotron oscillations randomize the motion of charged particles in an adiabatic trap. When the amplitude of the cyclotron wave is considerable, the randomization is due to the resonance of the longitudinal oscillations between the magnetic mirrors with transverse oscillations in the cyclotron wave field. If the amplitude is moderate, then the effect is due to phase shift at the resonance point. It is demonstrated that in the latter case the loss of particles from the trap may be insignificant, provided the oscillations have a short wave-length and the plasma is collisionless.
Influence of surface absorption on cyclotron oscillations in bounded systems