Enhanced phase space diffusion due to chaos in relativistic electron-whistler mode wave particle interactions with applications to Jupiter

Using numerical solutions of single-particle dynamics, we consider a chaoti c electron-whistler interaction mechanism for enhanced diffusion in phase s pace. This process, when applied to parameters consistent with the Jovian m agnetosphere, is a candidate mechanism for pitch angle scattering in the Io torus, thus providing a source of auroral precipitating electrons. We init ially consider the interaction between two oppositely directed monochromati c whistler mode waves. We generalize previous work to include relativistic effects. The full relativistic Lorentz equations are solved numerically to permit application to a more extensive parameter space. We use this simplif ied case to study the underlying behaviour of the system. For large-amplitu de monochromatic waves the system is stochastic, with strong diffusion in p hase space. We extend this treatment to consider two oppositely directed, b road band whistler wave packets. Using Voyager 1 data to give an estimate o f the whistler wave amplitude at the Io toms at Jupiter, we calculate the d egree of pitch angle scattering as a function of electron energy and initia l pitch angle. We show that for relatively wide wave packets, significant p itch angle diffusion occurs (up to +/- 25 degrees), on millisecond timescal es, for electrons with energies from a few keV up to a few hundred keV. (C) 2001 Elsevier Science Ltd. All rights reserved.