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 $\frac{(\omega +l\Omega )}{k_z}$. If the wave amplitude ${\Phi }_0$ is sufficiently large, neighboring resonant regions overlap, and the particle motion becomes stochastic; the threshold condition is ${k_z}^2\left(\frac{e}{m}\right){\Phi }_0\left|J_l\right(k_{\perp }\rho \left)\right|\approx \frac{{\Omega }^2}{16}$. As an application, a weakly damped intermediate-frequency ion-acoustic wave may be used to heat the tail of an ion distribution.