NONLINEAR PARALLEL ALFVEN WAVES IN COMETARY PLASMAS

In view of applications to cometary plasmas, a self-consistent reductive perturbation treatment is given for parallel propagation of MHD waves in cold plasmas, with a particular emphasis on a multispecies description in which different plasmaconstituents can have differing equilibrium drifts. The wave magnetic field is shown to obey a derivative nonlinear Schrödinger equation. Soliton solutions to this equation are discussed, including applications to cometary plasmas, where slow cometary ions are picked up by the fast flowing solar wind. Such solitons are, at a given maximum amplitude, wider than those in the nonstreaming case. © 1990.