Ion-acoustic solitons in magnetized multi-component plasmas including negative ions

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Abstract
A study is made of ion-acoustic solitons in a low-β magnetized plasma consisting of any number of adiabatic positive and negative ion species in addition to the presence of isothermal electrons. A KdV equation in three dimensions or KdV-ZK equation is derived. This equation admits comprehensive or rarefactive solitons propagating in any oblique direction with respect to the direction of the external magnetic field, depending on the density of the negative ion species. When the nonlinear coefficient of this equation vanishes, the nonlinear ion-acoustic wave is described by a modified KdV equation in three dimensions. This equation is also derived and its solitary-wave solutions are discussed. Both compressive and rarefactive solitons are possible. Finally, the three-dimensional stability of these solitons is investigated by the small-k perturbation expansion method of Rowlands and Infeld. Stability criteria and growth rates of instabilities are derived.