The role of nonlinear interaction in the formation of LF whistler turbulence upstream of a quasi-perpendicular shock

The role of the nonlinear interaction in developed low-frequency turbulence has been experimentally studied upstream of the ramp of a quasiperpendicul ar shock. The study has been carried out by application of the methods of b ispectral analysis and wavelet decomposition to the Active Magnetospheric P article Tracer Explorer Ion Release Module and Interball Tail Probe magneti c field data. It is shown that three-wave processes play a key role in the formation of the spectrum of the turbulence. Experimental results presented and previous theoretical considerations lead to the conclusion that energy is transfered from a narrow maximum frequency pumped by nonlinear dynamic processes to lower and higher frequencies.