HR: 11:30h
AN: SM21C-05 INVITED     [PDF]
TI: Alfven wave produced auroras during substorms
AU: * Mende, S B
EM: mende@ssl.berkeley.edu
AF: Space Sciences Lab, University of California at Berkeley, Centennial at Grizzly Peak, Berkeley, CA 94720 United States
AU: Frey, H U
EM: hfrey@ssl.berkeley.edu
AF: Space Sciences Lab, University of California at Berkeley, Centennial at Grizzly Peak, Berkeley, CA 94720 United States
AU: Carlson, C W
EM: cwc@ssl.berkeley.edu
AF: Space Sciences Lab, University of California at Berkeley, Centennial at Grizzly Peak, Berkeley, CA 94720 United States
AB: IMAGE FUV observations when the FAST satellite transits the aurora have provided evidence that Alfven wave-dominated aurora play a significant part in substorm aurora. In the FAST satellite data, Alfven wave dominated aurora can be distinguished from "inverted V" produced auroras that are accelerated by field aligned electric fields by the dominance of high fluxes of low energy electrons with beam like field aligned pitch angle distribution and accompanying strong wave activity. Each FAST transit provides a snapshot of the spatial morphology of the precipitating particles, field aligned current profiles and the fluctuating E and BM fields. We have examples of FAST transits with simultaneous IMAGE FUV observations during various stages of magnetospheric substorms and in temporary auroral intensifications so called pseudo-break ups. Most often such Alfvenic aurora is located at the poleward edge of the substorm surge arc, however there are examples of Alfven wave produced auroras in the center of the auroral region while surrounded by other types of aurora. One case when a FAST pass occurred approximately one minute after substorm onset showed that the most intense onset aurora was produced by Alfven wave accelerated super-thermal electrons and that this aurora was located well equatorward of the open closed field line boundary. Within the auroral feature the low energy ion fluxes showed periodic fine structure in the ExB direction and the magnetometer measurements also confirmed the presence of waves in this feature. In contrast to several substorm models the intense surge was not produced by a field aligned quasi-static electric field. The onset arc was also the poleward boundary of the intense energetic protons. Equatorward of the surge, there was a broader region of electron precipitation with embedded quasi-static "inverted V" electric fields. The FAST particle and magnetometer measurements are consistent with a field-aligned current structure in which the bulk of the upward current was carried by the "inverted V" precipitation region. The wave accelerated electron auroras are produced by converting the high intensity wave energy (Poynting) fluxes into electron energy and therefore the Alfven wave accelerated auroras are footprints of regions of the magnetosphere where magnetic reconfigurations take place.
DE: 2704 Auroral phenomena (2407)
DE: 2716 Energetic particles, precipitating
DE: 2736 Magnetosphere/ionosphere interactions
DE: 2740 Magnetospheric configuration and dynamics
DE: 2788 Storms and substorms
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting