Ion dynamics in multiple electrostatic waves in a magnetized plasma. II. Enhancement of the acceleration

The maximal energy an ion can gain from a discrete spectrum of electrostatic waves propagating perpendicularly to a uniform magnetic field is investigated. In the case when the wave spectrum contains at least two on-resonance waves, the ion is shown to reach energies which are much higher than in the case of one wave. When the ion energization is enhanced, even when the ion motion is not coherent, the ion orbit remains close to orbits found from a first order perturbation analysis. This implies that, unlike in the case of a single wave, the ion can reach high energies regardless of how small the wave amplitudes are. The dependence of the ion energization on the wave spectrum characteristics is described in great detail by deriving the extent, in action, of the first order orbits, and the way these orbits may connect. (C) 1998 American Institute of Physics. [S1070-664X(98)02609-3].