Resonance broadening induced nonlinear saturation of kinetic Alfvén turbulence in the interplanetary plasma

Abstract The saturation of ion-cyclotron Alfven turbulence excited by beam particles is investigated using the resonance broadening theory. The stochastic scattering which decorrelates particles, includes both random acceleration by electric fields and a turbulent magnetic mirroring effect. Turbulent mirroring is shown to yield non-Gaussian corrections to the orbits even if the random electric and magnetic fields are Gaussian. The predicted steady-state turbulence level exhibits a peaked angular distribution, with a maximum near Θ ⋍ 60° .