Nonadiabatic motion of charged particles in axisymmetric mirror magnetic fields

Ensemble properties of nonadiabatic motion of charged particles in inhomogeneous magnetic fields have been studied to determine qualitatively how the exact motion of the ensemble departs from the adiabatic motion as the adiabaticity parameter is increased. In particular, this investigation is directed towards determining the parameter domain of validity of two models for nonadiabatic behaviour, (i) the Stochastic Diffusion Model (SDM) and (ii) Quantum-like Model (QLM). It has been found that the predictions of the QLM are well corroborated by the numerical experiments for smaller values of the adiabaticity parameter ε, while the SDM presumably takes over for values of ε greater than a certain critical value. The latter is indicated from the observation that the mean square deviation, <(Δμ)2>, of gyroaction μ around the mean μ-bar over the ensemble, is found to increase linearly with time for values of ε beyond the critical value, while below it, it remains constant. It is also found that the multiple lifetimes - a characteristic feature of the QLM -which are widely separated for smaller values of ε come close together in the region of the critical ε, and probably lose their characteristic identity for larger values of ε, where the SD model probably takes over. (author)