Simultaneous observations of the auroral oval in both hemispheres under various
conditions

T.J. Stubbs (1), R.R. Vondrak (1), N. Ostgaard (2), J.B. Sigwarth (1), and 
L.A. Frank (3)

(1) Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center
(2) Space Sciences Laboratory, University of California, Berkeley
(3) Department of Physics and Astronomy, University of Iowa


Recently, it has been possible to observe the entire auroral oval in both the
northern and southern hemispheres simultaneously with the IMAGE FUV imagers and
Polar VIS Earth camera, respectively. These rare opportunities allow us to study
conjugate and non-conjugate effects on a global scale under various interplanetary
conditions; thus enabling us to better understand the transfer of mass and energy
from the solar wind to the magnetosphere/ionosphere system. The events we study
here are from late 2002 with periods of simultaneous observation lasting between
about 30 and 50 minutes. Most events are associated with a steady IMF BX
component, where the IMF BY and BZ components vary. The locations of the
"centroid" of the auroral ovals, which allow us to track their motion, are
determined using a circle fitting routine. Initial results have shown the expected
IMF BY -dependent asymmetry along the dawn-dusk meridian; however, in the event
studied there was also an overall dawnward offset of the ovals in both
hemispheres. Under conditions of strong IMF BX > 0 and weak IMF BZ > 0, we have
observed the southern oval move equatorward relative to the northern oval,
consistent with tail lobe reconnection occurring only in the southern hemisphere.

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Presented at the 35th COSPAR Scientific Assembly, Paris, France, July 18-25, 2004.