HR: 10:20h
AN: SM42A-01 INVITED     [Abstracts]
TI: Ionospheric Structuring in Alfven waves
AU: * Chaston, C C
EM: ccc@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California 7 Gauss Way , Berkeley, CA 94720, United States
AU: Hull, A J
EM: ahull@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California 7 Gauss Way , Berkeley, CA 94720, United States
AU: Genot, V
EM: vincent.genot@cesr.fr
AF: Centre d'Etude Spatiale des Rayonnements, 9 Av Colonel Roche, Touoluse, 31400, France
AU: Bonnell, J W
EM: jbonnell@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California 7 Gauss Way , Berkeley, CA 94720, United States
AU: Carlson, C W
EM: cwc@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California 7 Gauss Way , Berkeley, CA 94720, United States
AU: McFadden, J P
EM: mcfadden@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California 7 Gauss Way , Berkeley, CA 94720, United States
AU: Ergun, R E
EM: ree@lasp.boulder.edu
AF: Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Co 80303, United States
AU: Strangeway, R J
EM: strange@igpp.ucla.edu
AF: Institute for Geophysical and Planetary Physics, 405 Hilgard Ave University of California, Los Angeles, CA 90095, United States
AB: We show observations from the FAST satellite indicating that dispersive Alfven waves erode the topside auroral ionosphere. Observations from a case study example show that Alfven waves become focussed into density depressions and through a cascade to small scales drive mass outflow from these depressions to form deep cavities where the ionospheric plasma may be depelted by more than 90 percent. This process is self sustaining in the sense that deeper cavities stimulate more rapid production of small scale waves and hence further mass outflow. The intense density gradients within these cavities are shown to support double layers driven by the Alfven wave current which is intensified through ionospheric feedback. Observations show that this process can occur over an extended latitudinal range leading to a highly depleted/fragmented density profiles over the altitude range traversed by the FAST sateliite (350-4100 km). We present statistical measurements indicating that this process commonly occurs whenever Alfven waves on small scales are observed from the FAST satellite in and above the topside ionosphere.
DE: 2407 Auroral ionosphere (2704)
DE: 2704 Auroral phenomena (2407)
DE: 2721 Field-aligned currents and current systems (2409)
DE: 2736 Magnetosphere/ionosphere interactions (2431)
DE: 2772 Plasma waves and instabilities (2471)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Joint Assembly