Stochastic pitch angle diffusion due to electron-whistler wave-particle interactions

In the Earth's magnetosphere, electron-whistler mode wave-particle interact ions are a candidate mechanism for auroral precipitation via electron phase space diffusion. Of particular interest are stochastic interactions betwee n relativistic electrons and (as often observed) waves of more than one wav e number. It can be shown that the interaction between electrons and two op positely directed monochromatic whistlers is stochastic. Once a threshold i s exceeded, stochastic trajectories exist in addition to regular orbits (Ko lmogorov-Arnold-Moser, or KAM, surfaces) near resonance, and here their cor responding pitch angle diffusion is estimated. The treatment is extended to consider broad band whistler wave packets and it is shown that the stochas tic diffusion mechanism is again present for interactions with one or two w ave packets. The pitch angle diffusion coefficient is estimated from the dy namics of stochastic electrons. For wave amplitudes consistent with planeta ry magnetospheres, such as at the Earth and Jupiter, pitch angle diffusion due to stochastic interactions occurs on fast (millisecond) time scales res ulting in significant increases in the pitch angle diffusion coefficient. ( C) 2001 American Institute of Physics.