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T.S. Stallard, S. Miller, H. Melin (UCL), L. Trafton (University of Texas), M. Dougherty, N. Achilleos (Imperial College)
We are currently undertaking a long-term observing program studying Saturn's infrared aurora, using the CSHELL high-resolution spectrometer on NASA's IRTF to measure line emission from auroral H3+, as a part of the Cassini support program. Using these measurements, we are able to resolve spatial and temporal variations in the H3+ auroral emission and the associated ion wind speeds. We present the current developments in our research, based upon recent observations. We are able delineate a number of separate velocity regions within the auroral oval and can show that these regions vary over an extended time period. We have also measured variations in both overall intensity and morphology of the auroral emission, which appear to be correlated with changes in the velocity structure.
Our Doppler shift velocities have previously shown that the polar region as a whole sub-corotates, attenuated from the assumed velocity of the neutral atmosphere. This general trend has been resolved into a number of separate regions within the auroral oval; under 'normal' conditions, when the auroral region appears to emit as a filled ring, three regions of differing wind velocity are shown within the pole. At times when there is asymmetric emission across the polar region these velocity regions appear to be reduced or removed entirely. Using the variation in intensity across the auroral region, we can thus categorise the varying velocity structure and relate these to observations previously made in the UV, and to theories explaining such emission structure.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.