Long time behaviour of marginally stable magnetomodulational perturbation

The long time behaviour of magnetomodulational perturbation has been investigated by using multiple time scale perturbation method. If the perturbation field is purely potential, it is found that unlike ordinary modulational unstability the magnetomodulational instability persists in the nonlinear stage of evolution. The exact analytical solution obtained for the marginally stable mode of the linear theory exhibits explosively unstable behaviour in the slow time scale. When both potential and solenoidal components of perturbation are present the transverse exerts a stabilising influence. Different kinds of long time behaviour may occur as medicated by the results of the numerical integration of the coupled nonlinear evolution equations for the Langmuir and transverse fields. (author)