Stochastic Acceleration by a Single Wave in a Magnetic Field

Abstract

The nature of a particle orbit in an electrostatic plasma wave is modified by a magnetostatic field, because there exists a set of resonant parallel velocities $\frac{(\ensuremath{\omega}+l\ensuremath{\Omega})}{{k}_{z}}$. If the wave amplitude ${\ensuremath{\Phi}}_{0}$ is sufficiently large, neighboring resonant regions overlap, and the particle motion becomes stochastic; the threshold condition is ${{k}_{z}}^{2}(\frac{e}{m}){\ensuremath{\Phi}}_{0}|{J}_{l}({k}_{\ensuremath{\perp}}\ensuremath{\rho})|\ensuremath{\approx}\frac{{\ensuremath{\Omega}}^{2}}{16}$. As an application, a weakly damped intermediate-frequency ion-acoustic wave may be used to heat the tail of an ion distribution.