HR: 0800h
AN: SM51A-1273    [Abstracts]
TI: Bounce Resonant Instabilities of Kinetic Alfvén Waves on Auroral Field Lines
AU: * Lysak, R L
EM: bob@aurora.space.umn.edu
AF: School of Physics and Astronomy University of Minnesota, 116 Church Street SE, Minneapolis, MN 55406 United States
AU: Song, Y
EM: yan@aurora.space.umn.edu
AF: School of Physics and Astronomy University of Minnesota, 116 Church Street SE, Minneapolis, MN 55406 United States
AB: Recent observations from the FAST satellite as well as a number of sounding rocket missions have shown two distinct modes of auroral electron acceleration: the classic inverted-V signature consisting of a beam broad in pitch angle but narrowly confined in energy, and a lower energy, field-aligned acceleration that has been attributed to kinetic Alfvén waves. Moreover, observations indicate that these two particle populations often co-exist, suggesting that Alfvénic acceleration can occur on field lines with a quasi-static potential drop. Electrons of appropriate energy and magnetic moment can be trapped between this potential drop and their magnetic mirror points. Calculations indicate that trapped electrons of a few hundred electron volts have bounce periods of 1-5 seconds, comparable to the period of waves in the ionospheric Alfvén resonator, a structure produced by the gradients in the Alfvén speed above the auroral ionosphere. This suggests that a bounce resonant instability may occur that would excite waves in the resonator that could play a role in the acceleration of low-energy field-aligned electrons. A non-local kinetic theory including trapped electrons has been developed to determine what role such bounce resonance plays in the auroral acceleration process.
DE: 2704 Auroral phenomena (2407)
DE: 2736 Magnetosphere/ionosphere interactions (2431)
DE: 7827 Kinetic and MHD theory
DE: 7836 MHD waves and instabilities (2149, 2752, 6050)
DE: 7867 Wave/particle interactions (2483, 6984)
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005