Stability of a modulated ion acoustic wave in a magnetised plasma.

A nonlinear Schrodinger equation which governs the nonlinear interaction of the ion-acoustic wave with the quasistatic plasma slow response in a magnetised plasma is deduced. The magnetic field is assumed to be constant. It is observed that the coefficient of the nonlinear term in the derived nonlinear Schrodinger equation turns out to be complex, in contrast to the usual situation. The condition for modulational stability is derived and it is found to be somewhat different. In the final section such a condition is discussed graphically. Our NLS equation goes back to that of the unmagnetised case if wc is put to zero.