A new decay channel for compressional Alfven waves in plasmas

We present a new efficient wave decay channel involving nonlinear interactions between a compressional Alfven wave, a kinetic Alfven wave, and a modified ion sound wave in a magnetized plasma. It is found that the wave coupling strength of the ideal magnetohydrodynamic (MHD) theory is much increased when the effects due to the Hall current are included in a Hall-MHD) description of wave-wave interactions. In particular, with a compressional Alfven pump wave well described by the ideal MHD theory, we find that the growth rate is very high when the decay products have wavelengths of the order of the ion thermal gyroradius or shorter, in which case they must be described by the Hall-MHD) equations. The significance of our results to the heating of space and laboratory plasmas as well as for the Solar corona and interstellar media are highlighted.