Generation of zonal flows by kinetic Alfven waves

The generation of zonal flows by kinetic Alfven waves is analyzed. It is noted that the basic approach underlying the existing theory of this phenomenon is too simplified because it attributes the generation of zonal flows to instabilities of an individual monochromatic wave packet of kinetic Alfven waves. It is shown that, when a monochromatic wave packet is stable, it is necessary to analyze a more complicated situation with a double-peak packet (or, in the simplest case, with two pump waves). It is found that, for a double-peak packet of kinetic Alfven waves, there is a new class of instabilities of zonal flows and that these instabilities are analogous to two-stream instabilities in linear theory. The main types of such instabilities are investigated