Evolution of nonlinear Alfven waves in streaming inhomogeneous plasmas

A nonlinear evolution equation for Alfven waves, propagating in streaming p lasmas with nonuniform densities and inhomogeneous magnetic fields, is obta ined by using the reductive perturbation technique. The governing equation is a modified derivative nonlinear Schrodinger (MDNLS) equation. The numeri cal solution of this equation shows that inhomogeneities exhibit their pres ence as an effective dissipation. The spatiotemporal evolution of long-wave length Alfvenic fluctuations shows that the wave steepens as it propagates. High-frequency radiation is also observed in our simulations. Unlike coher ent Alfven waves in homogeneous plasmas, which can become noncoherent/chaot ic only in the presence of a driver, MDNLS evolves into noncoherent/turbule nt state without any driver simply because of inhomogeneities. This clearly indicates that the integrability property of the derivative nonlinear Schr odinger equation, which allows coherent solitary solutions, is destroyed by inhomogeneities.