Nonlinear Processes in Geophysics www.nonlin-processes-geophys.net 1023-5809 1607-7946 9 2 2002 10.5194/npg-9-87-2002 http://www.nonlin-processes-geophys.net/9/87/2002/ http://www.nonlin-processes-geophys.net/9/87/2002/npg-9-87-2002.html http://www.nonlin-processes-geophys.net/9/87/2002/npg-9-87-2002.pdf 87 99 0000-00-00 Nonlinear waves and solitons propagating perpendicular to the magnetic field in bi-ion plasma with finite plasma pressure E. M. Dubinin K. Sauer J. F. McKenzie G. Chanteur Max-Planck Institut für Aeronomie, Katlenburg-Lindau, Germany School of Pure and Applied Physics, University of Natal, Durban, South Africa Centre d’Etude des Environnements Terrestre et Planetaires, Velizy, France 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.