Search

We investigate the nature of nonlinear waves propagating transverse to the magnetic field in a bi-ion plasma including plasma pressure. By using the conservation laws derived from the multi-ion fluid equations the system may be described by a single order differential equation whose properties control the structure of the flow and the magnetic field. Compressive solitons exist in specific ranges of the characteristic Mach numbers. Various features of solitons differ in different existence "windows". For example, there are solitons that contain a strong proton rarefaction core embedded in the main compressional structure. Compressive solitons are found in a wide range of flow parameters. Finite ion pressure introduces critical Mach numbers. In contrast to a plasma consisting only of protons and electrons these singular points are reached where a specific combination of ion and electron speeds lies on particular locii, in multi-parameter space, which corresponds to the generalized "sonic point" of the compound system.

Extensive one‐dimensional Vlasov simulations have been performed in order to study the dynamics of double‐layer generation in a stable current carrying plasma. An initial density perturbation, which shortly builds a potential well, leads to a weak double layer and to a recurrent formation of electron vortices for a large range of temperature ratios and electron drift velocities. The electron–vortex formation is inhibited for very small velocity drifts. While the electrostatic energy is generally almost constant, a weak growth develops for an electron drift velocity that is sufficiently high, but less than the critical drift velocity for marginal stability. The amplitude of individual double layers is rather weak, but the collision of two double layers drives a nonlinear instability related to the fusion of electron vortices, amplifying the double‐layer potential to several times the electron thermal energy.

A pseudo-spectral scheme, following an idea of Fornberg and Whitham is proposed to integrate a dissipative KdV equation derived by Ott and Sudan.