Laboratory Investigation of Nonlinear Subcyclotron Damping

Triggered emissions experiments conducted in the Space Physics Simulation Chamber at the Naval Research Laboratory (NRL) have shown electron beam driven whistler turbulence that exhibits cutouts in the observed spectrum at approximately 1/2 and 1/3 of the electron cyclotron frequency. Similar gaps are observed in whistler chorus from satellite measurements. It has been suggested that nonlinear subcyclotron resonances could be a mechanism for the formation of these gaps, where nonlinear resonances at subharmonics can form due to the perturbed particle motion in the fields from the wave. A series of laboratory experiments are being conducted to test whether these observed gaps could be formed by this mechanism. Recent results from these experiments will be presented.