Thermalization of Neutral-Beam-Injected Ions by Lower Hybrid Waves in Jupiter's Magnetosphere

A theoretical analysis of lower hybrid wave generation by a ring distribution of superthermal ions is presented. A kinetic instability of waves traveling across the magnetic field occurs when fast neutrals escaping from the Io plasma torus are reionized and accelerated to corotation speed in Jupiter's magnetosphere. Instability is possible for modest threshold vaules of $\frac{V}{a_0}=3-7\mathrm{}$ where $V$ is the pickup gyrospeed and $a_0$ is the background-ion thermal speed. Consequent effects include the relaxation of the pickup-ion distribution and the acceleration of superthermal electrons.