Nonlinear Hydromagnetic Solitary Waves in a Collision-Free Plasma with Isothermal Electron Pressure

Nonlinear hydromagnetic solitary waves propagating in a collision-free plasma of cold ions and isothermal electrons are investigated on the basis of hydrodynamical transport equations. Both cases of wave propagation along and across a magnetic field are studied in detail. In the parallel case, two types of solitary wave are found. The first type is an ordinary one which reduces to the zero-pressure wave in the cold limit and the other is a particular one which has no counterpart in the cold plasma. In the transverse case, only one type of solitary wave similar to that in the cold plasma is found. The effect of electron pressure shortens the relative widths of the waves in the parallel case (for the first type) while widens those in the transverse case. Magneto-ion-dynamics is formulated for the plasma under consideration, where the relation between the two-fluid model and the one-fluid magneto-hydrodynamics is established.