NONLINEAR ALFVEN-WAVE PHENOMENA IN THE PLANETARY MAGNETOSPHERE

Three nonlinear Alfven wave phenomena in the planetary magnetosphere a re discussed: (1) magnetohydrodynamic parametric instabilities induced by a nonlinear standing Alfven wave, (2) parametric excitation of Alf ven and Langmuir waves by a nonlinear electromagnetic whistler wave, a nd (3) parametric generation of electromagnetic waves in the vicinity of electron plasma frequency via nonlinear coupling of Langmuir and Al fven waves. Observational evidence in support of these nonlinear Alfve n wave phenomena, such as the auroral Alfven-acoustic turbulence and t he auroral Langmuir-Alfven-whistler (LAW) events, in the planetary mag netosphere is presented.