Generation of kinetic Alfven waves by upper-hybrid pump waves

The nonlinear mechanism for kinetic-Alfven-wave (KAW) excitation by upper-h ybrid waves (UHWs) is discussed. Taking into account perpendicular dispersi on of KAWs; caused by effects of finite ion Larmor radius and electron iner tia, me examine a new channel for UHW decay, in which a pump UHW decays int o another UHW and an ultralow-frequency wave, KAW: UHW --> KAW + UHW. A non linear dispersion relation is derived, and the growth rate of the parametri c decay instability is calculated for a pump UHW propagating at an arbitrar y angle to the back ground magnetic field. We find that the resulting KAWs often have a two-peaked spectrum with different perpendicular dispersions. Using satellite observations, the analytical results are applied to show th at the considered process represents an effective mechanism for KAW generat ion and the consequent spreading of the UHW spectrum in the Earth's magneto sphere and solar corona.