Density cavities associated with inertial Alfven waves in the auroral plasma

We have investigated the nonlinear interaction between inertial Alfven waves and ion-acoustic waves by numerical simulation and showed that the system becomes more chaotic and turbulent as it evolves. The nonlinear dynamical equation satisfies modified Zakharov type of equations by taking the nonadiabatic response of the background density. The evolution of density cavities corresponding to magnetic field coherent structures are found at different times. The deepest density depletion, which is accompanied by most intense magnetic fields, has the density fluctuations of similar to 0.4n(0) and similar to 0.6n(0) (n(0) is electron number density) for auroral and coronal plasmas, respectively. As a result of the ponderomotive force, the magnetic field is trapped in the regions of low density. The power spectrum of magnetic field fluctuations indicates that the nonlinear interactions may be distributing energy among higher wave numbers.