Effects of phase-bunching in strongly turbulent plasmas

The effects of phase bunching on the collisionless dissipation of nonlinear wave fields is explored, with emphasis on situations relevant to strong tu rbulence applications. It is argued that in a homogeneous, steady-state pla sma, there is no preferred phase of the electric field experienced by parti cles as they enter a wave packet. However, an initially phase-uniform ensem ble of particles will generally be phase-bunched after interacting with a w ave packet. This can lead to a dramatically intensified interaction with su bsequent packets encountered by the particles. Numerical calculations revea l that the local wave dissipation can increase by orders of magnitude if th e transiting particles have been phase-bunched prior to entering a wave pac ket. The wave particle interactions, called transit-time dissipation, compr ise Landau damping and a nonresonant type of damping. The nonresonant dampi ng causes a redistribution of field energy within a wave packet. This effec t is particularly strong in phase-bunched systems. These results may force modifications to previous treatments of strong turbulence which have assume d isotropy and homogeneity, and employed standard Landau damping. (C) 2000 American Institute of Physics. [S1070-664X(00)01209-X].