Nonlinear Excitation Of Ion-acoustic Modes By Rf Waves

We have detected a slow ion-acoustic wave propagating obliquely to the equilibrium magnetic field in a low-density, weakly ionized helium plasma produced by rf power in the linear mirror machine LISA. When an upper hybrid wave is launched perpendicular to the ambient magnetic field, we have observed that the upper hybrid wave decays parametrically into another upper hybrid wave and a slow ion-acoustic wave. © 1992 The American Physical Society.45107640764