HR: 15:00h
AN: SM53D-06    [Abstracts]
TI: Wave propagation and the formation of fine auroral structure: New constraints derived from high-speed imagery
AU: * Semeter, J
EM: jls@bu.edu
AF: Boston University, Department of Electrical and Computer Engineering, Boston, MA 02215, United States
AU: Mende, S
EM: mende@ssl.berkeley.edu
AF: University of California at Berkeley, Space Sciences Laboratory, Berkeley, CA 94720, United States
AU: Zettergren, M
EM: mattzett@bu.edu
AF: Boston University, Department of Electrical and Computer Engineering, Boston, MA 02215, United States
AU: Diaz, M
EM: mdiaz@bu.edu
AF: Boston University, Department of Electrical and Computer Engineering, Boston, MA 02215, United States
AB: An analysis of simultaneous multi-scale observations of a discrete auroral breakup is presented, which clarifies the potential role of plasma wave dispersion in the formation of fine-scale auroral structure. At coarse resolution (all-sky white light camera, 1 frame/s), observations fit the established description of an arc breakup: (1) arc brightening, (2) formation of spatial distortions, and (3) breakup into multiple 'rayed' structures. At fine-scale resolution (EMCCD camera, 9 degree field of view, prompt emission filter, 30 frames/s), an entirely different type of coherence is observed. The 'arc' is observed to be a wave packet composed of parallel bifurcating ~100-m structures which propagate outwards from the center and fade. The bifurcation process is hierarchical, with newly formed substructure further bifurcating into subordinate auroral forms as the fading proceeds. The observations are well represented by a model that invoking electron acceleration in a dispersive phase-coherent wave field propagating into the topside ionosphere. This empirical model is discussed in the context of dispersive shear Alfven waves at the near-Earth magnetosphere.
UR: http://people.bu.edu/jls
DE: 2431 Ionosphere/magnetosphere interactions (2736)
DE: 2471 Plasma waves and instabilities (2772)
DE: 2704 Auroral phenomena (2407)
DE: 2752 MHD waves and instabilities (2149, 6050, 7836)
DE: 2794 Instruments and techniques
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting