Two-dimensional dynamics of ion-acoustic waves in a magnetised electronegative plasma

We consider a plasma model made of negative ions and electrons in Boltzmann distribution and cold mobile positive ions, under the influence of an external magnetic field, to study the propagation of ion-acoustic waves (IAWs). From the hydrodynamic equations of the two-dimensional (2D) electronegative plasma, the dynamics of the system is reduced via the reductive perturbation method to the Davey–Stewartson (DS) equations. Using the linear stability analysis of planar waves, an expression of the modulational instability growth rate is derived, and its response to system parameters, such as the negative ion concentration ratio, the electron-to-negative ion temperature ratio and the magnetic field is discussed. It comes out that the instability occurs for high values of the negative ion concentration ratio and in a very restrained area of small magnetic field values. The growth rate is maximum for high values of both the electron-to-negative ion temperature ratio and the magnetic field. The existence of IAWs in the model is confirmed. One-dromion and two-dromion solutions are investigated analytically using the Hirota’s bilinear method and numerically. The impact of the magnetic field is discussed in that context, and particular attention is given to dromion interactions under different scenarios. We noted a slowing effect on the propagation of the dromion solutions in the presence of the magnetic field. Elastic collision of two-dromion solutions is observed during their evolution, with an acceleration of the process in the presence of the magnetic field.