Energetic tail evolution of auroral electron spectra

Based on a Fokker-Planck formalism a mechanism is presented, generating consistent with spacecraft observations a high energy tail electron population from the interaction of a broad-band Alfvén wave spectrum under auroral plasma conditions. The structure of the resulting suprathermal tails of the electron velocity space distributions is shown to be well represented by the family of kappa distributions, hence providing a physical interpretation of the origin of auroral energetic electron observations.