[PEM11-08] Effects of initial density fluctuations on linear and nonlinear evolution of parametric decay instabilities of circularly polarized Alfven waves
Keywords:Alfven wave, parametric instability, solar wind plasma
In this presentation, we discuss roles of initial density fluctuations on the decay instabilities of Alfven waves. Since not only parallel propagating waves but also obliquely propagating waves are unstable to the decay instability [Vinas+Goldstein, JPP, 1991], oblique initial density fluctuations with finite amplitude can preferentially be excited, even if their linear growth rates are not large. In such a case, the growth of the parallel propagating mode is usually suppressed. Numerical results of three-dimensional MHD simulation also show an opposite case, in which the linear growth of the parallel propagating modes is promoted by the effects of the multi-dimensionality. Dependence of linear and nonlinear evolution on wave number spectra of initial waves will be demonstrated.