Stochastic ion behavior in subharmonic and superharmonic electrostatic waves

The dynamics of a charged particle in a magnetic field perturbed by electrostatic waves propagating transverse to the magnetic field has been investigated. Depending on the number of perturbing waves, the magnitude of the perturbation and the perturbation frequency (v=r/s=omega/omega(0), where r and s are relatively prime integers, and omega(0) is the cyclotron frequency), the particle motion can exhibit either a small deviation from simple cyclotron motion or stochastic motion over phase space. The latter case is found to correspond to particle heating and anomalous transport. In the case of cyclotron harmonic perturbations (superharmonic case, s=1), the phase space of the particle is covered by a stochastic web, inside of which the particle motion is chaotic. The particle can, in principle, be heated to very high energy. However, if the wave frequency is some fraction of the ion cyclotron frequency (subharmonic case, s greater than or equal to 2), the heating range is limited. (C) 1996 American Institute of Physics.