Paper#: 70
Poster #:
Session Name: Workshop 4C: Waves and Instabilities
Room: 200ABC
Day: Wednesday
Time: 10:50-11:15 a.m.
Abstract Title: Low-Frequency Electron Kinetics on Auroral Field Lines
PresentSurname: Lysak, R.L.
All Authors: R.L. Lysak, Y. Song
Abstract : It has now become established that Alfvén waves can carry sufficient energy for auroral acceleration processes, especially during disturbed times. While these waves are often treated in the two-fluid approximation, kinetic theory must be used to describe particle acceleration due to these waves. In the plasma sheet boundary layer, where plasma gradients are weak, the local approximation can be used to describe the wave-particle interactions due to Alfvén waves. In this regime, Landau-resonant interactions can heat electrons along the magnetic field line, especially for higher values of the plasma beta and for short perpendicular wavelengths. These interactions can lead to strong damping of these waves, implying that their wave energy must be resupplied from nonlinear interactions. Closer to the Earth on auroral field lines, a non-local approach to the wave-particle interactions is necessary. This can give rise to bounce-resonant interactions for electrons whose bounce period is comparable to the wave period. For example, a 1-keV electron bouncing in the dipole field has a bounce period of a few seconds, comparable to the period of waves in the ionospheric Alfvén resonator. A Fermi-type acceleration can occur for backscattered electrons emitted from the ionosphere that encounter an incoming Alfvén wave on auroral field lines, which can give rise to further backscattered and secondary electrons trapped between the ionosphere and the peak in the parallel electric field of the Alfvén wave.