HR: 09:10h
AN: SM21A-05 INVITED     [PDF]
TI: The Structure and Dynamics of Poynting Flux in the Geomagnetic Tail and its Role in Generating Aurora
AU: * Wygant, J R
EM: wygant@ham.space.umn.edu
AF: University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455
AB: Recent observations from the Polar and Cluster spacecraft have provided evidence that a variety of processes observed in different locations in the geomagnetic tail during intervals of strong magnetic activity generate intense Alfvenic and steady state Poynting flux directed along magnetic field lines towards the Earth. This Poynting flux is often capable of providing the power necessary for the acceleration of auroral electrons and creating intense auroral displays. Strong electric and magnetic fields associated with MHD waves carrying Poynting flux directed towards the Earth are observed in the high beta plasma sheet near 9 Re during repetitive intervals of magnetic field dipolarization during major geomagnetic storms. Intense Poynting flux associated with Alfvenic surface waves have been also been observed in the low beta Plasma sheet boundary layer (PSBL) at altitudes of 4-7 Re immediately above the auroral acceleration region near the poleward boundary of the auroral zone. During the main phase and peak of major geomagnetic storms, measurements of electric and magnetic fields from Polar in the near Earth equatorial plasma sheet show evidence for spatially extensive (1-3 Re) regions of intense Poynting flux (both steady state and Alfvenic) towards the Earth. This Poynting flux maps to low latitudes over widths of 2-5 degrees. Finally, observations from the Cluster spacecraft studies demonstrate that strong Poynting flux is radiated from the reconnection region near ~20 Re in association with magnetic field energy conversion in the tail. The in-situ values of Poynting flux from these regions are 0.1 to 1.0 mW/m2 and may be related to the observations in the PSBL The value of Poynting flux mapped to altitudes of 100 km are on the order 10-100 mW/m2 and are sufficient to power some of the most intense aurora observed in the Polar spacecraft UV Image and the IMAGE spacecraft WIC data sets. The properties of the structure and dynamics of the MHD waves associated with the Poynting flux will be summarized and compared to the temporal and spatial structure of the auroral forms simultaneously observed by the IMAGE and Polar Space based imagers.
DE: 2704 Auroral phenomena (2407)
DE: 2740 Magnetospheric configuration and dynamics
DE: 2744 Magnetotail
DE: 2764 Plasma sheet
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting