Fokker-Planck modeling of auroral wave-particle interactions

Observations of electron velocity distributions in the auroral zone, carried out by spacecraft and by rockets, have found high-energy, magnetic field-aligned, suprathermal tails in regions where strong wave activity in the lower hybrid range of frequencies is also detected. A causal link between these observations could in principle arise from quasi-linear diffusion of the electrons, driven by Landau resonant lower hybrid waves. To investigate this, a two-dimensional finite difference Fokker-Planck code has been written. The results of the numerical investigations carried out with this code indicate that the observed lower hybrid wave intensities are sufficient to produce strongly nonthermal electron distributions, which are similar to those observed