Study of kinetic Alfven wave and whistler wave spectra and their implication in solar wind plasma

This work presents the numerical simulation of the nonlinear evolution of kinetic Alfven wave (KAW), in a parametric regime consistent with the solar wind plasmas. The nonlinear dynamical equation of KAW satisfies the modified nonlinear Schrodinger equation when incident pump KAW has a small perturbation. Numerical simulation has been done to solve this model equation when the ponderomotive nonlinearity is incorporated in the KAW dynamics. The localization of pump KAW as a consequence of ponderomotive nonlinearity has been studied in the solar wind at 1 AU. A weak whistler signal propagating in these localized structures is amplified and leads to the development of its own localized structures. Magnetic power spectra and spectral indices for KAW at different times are calculated. The magnetic field power spectra and spectral indices of whistler wave at different times are also calculated. The relevance of steepened KAW and whistler spectra to recent solar wind observations is also pointed out. These localized structures and steeper spectra can be responsible for the plasma heating and particles acceleration in solar wind.