Nonlinear evolution of slow waves in the solar wind

We show by numerical simulation using a hybrid code that comparison of the nonlinear steepening rate, calculated from fluid theory, with the linear collisionless damping rate, defines reasonably well the parameters for which fast and slow MHD waves should steepen. Our results indicate that, whereas fast modes should ordinarily steepen, steepened slow waves should occur rarely in the solar wind near 1 AU.