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N.M Schneider, M.H Burger, S.E. Sutton, M.A. Dubson (LASP, University of Colorado)
Io's corona is the critical link between Io's atmosphere and the plasma torus. This region, from the exobase to the Hill sphere at about 6 RIo, has now been studied in enough detail to search for temporal variations, spatial asymmetries, and differences between atomic species. Our mutual eclipse observations reveal a relatively stable sodium corona with a significant asymmetry: Io's sub-Jupiter side is ~50% brighter than the anti-Jupiter side (Burger et al., ApJ 563, 2001). We also find that Io's sodium corona falls off more steeply than the oxygen corona (measured by HST, Wolven et al., JGR 106, 2001). This effect exceeds that expected from their different ionization potentials, and is better explained by electron cooling near Io.
Despite the promise of coronal studies, observations to date have required either the UV capability of HST or satellite mutual eclipses occurring every six years. We have undertaken an adaptive optics study of sodium in Io's corona to allow more routine diagnostic observations. Standard groundbased imaging suffers from the inevitable blurring of Io's 1.2"-wide disk with the 6" corona, fainter by up to 4 orders of magnitude. AO has the potential of imaging the corona by limiting the blurring of Io's disk. We will report on observations using the Air Force's 3.67m AEOS telescope at Haleakala, Maui, and our efforts to measure coronal emissions through rigorous differencing of on-band and off-band images.
This work has been supported by NASA's Planetary Astronomy program and NSF's Advanced Technology and Instrumentation program.
The author(s) of this abstract have provided an email address for comments about the abstract: nick.schneider@lasp.colorado.edu
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.