2 μm Spectrophotometry of Jovian Stratospheric Aerosols—Scattering Opacities, Vertical Distributions, and Wind Speeds
Identifieur interne : 000703 ( Main/Exploration ); précédent : 000702; suivant : 0007042 μm Spectrophotometry of Jovian Stratospheric Aerosols—Scattering Opacities, Vertical Distributions, and Wind Speeds
Auteurs : Don Banfield ; Peter J. Gierasch ; Steven W. Squyres ; Philip D. Nicholson ; Barney J. Conrath ; Keith MatthewsSource :
- Icarus [ 0019-1035 ] ; 1996.
Abstract
Narrow-band 2.0–2.35 μm spectrophotometric observations of Jupiter at nine wavelengths were taken with the 5-m Hale Telescope at Palomar during the month following the impact of Comet P/Shoemaker–Levy 9. Spectra were obtained for the principal impact sites, and also for regions not affected by the comet impacts (the South Polar Region, North Equatorial Zone, South Equatorial Zone, and the Great Red Spot). A technique by which near-infrared reflection spectra can be inverted to yield vertical profiles of scatterer density is presented. For our wavelengths and bandwidths, the sensitivity of the inversions extends from pressure levels near 1 bar up to about 20 mbar. We find that all comet-induced aerosol clouds lie near or above the vertical limit of our sensitivity, i.e., 20 mbar. The lower limit of the clouds is around 50 mbar. The total scattering opacity of the clouds decreased by a factor of about 1.7 over the 35 days spanned by these observations, while the area covered by them increased by a factor of about 1.5. Westet al.(West, R. A., E. Karkoschka, A. J. Friedson, M. Seymour, K. H. Baines, and H. B. Hammel 1995.Science267, 1296–1301.) suggest particle coagulation during this time which fits with our observations, but particle fallout is also likely. All the aerosols comprise a volume the equivalent ofa∼ 0.6-km radius sphere assuming a particle size of 0.25 μm. We also measured the drift speeds of these clouds using two different techniques. One involved scaling down Voyager-measured cloud-top winds (Limaye, S. S. 1986.Icarus65, 335–352.) and deforming early images to match later images, while the other involved directly cross-correlating longitudinally shifted images of spots from different times. Both techniques indicate wind speeds of order 5 m/sec, or ∼30% of the tropospheric wind speeds measured by Voyager in this region.
Url:
DOI: 10.1006/icar.1996.0095
Affiliations:
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Spectra were obtained for the principal impact sites, and also for regions not affected by the comet impacts (the South Polar Region, North Equatorial Zone, South Equatorial Zone, and the Great Red Spot). A technique by which near-infrared reflection spectra can be inverted to yield vertical profiles of scatterer density is presented. For our wavelengths and bandwidths, the sensitivity of the inversions extends from pressure levels near 1 bar up to about 20 mbar. We find that all comet-induced aerosol clouds lie near or above the vertical limit of our sensitivity, i.e., 20 mbar. The lower limit of the clouds is around 50 mbar. The total scattering opacity of the clouds decreased by a factor of about 1.7 over the 35 days spanned by these observations, while the area covered by them increased by a factor of about 1.5. Westet al.(West, R. A., E. Karkoschka, A. J. Friedson, M. Seymour, K. H. Baines, and H. B. Hammel 1995.Science267, 1296–1301.) suggest particle coagulation during this time which fits with our observations, but particle fallout is also likely. All the aerosols comprise a volume the equivalent ofa∼ 0.6-km radius sphere assuming a particle size of 0.25 μm. We also measured the drift speeds of these clouds using two different techniques. One involved scaling down Voyager-measured cloud-top winds (Limaye, S. S. 1986.Icarus65, 335–352.) and deforming early images to match later images, while the other involved directly cross-correlating longitudinally shifted images of spots from different times. Both techniques indicate wind speeds of order 5 m/sec, or ∼30% of the tropospheric wind speeds measured by Voyager in this region.</div></front></TEI><affiliations><list></list><tree><noCountry><name sortKey="Banfield, Don" sort="Banfield, Don" uniqKey="Banfield D" first="Don" last="Banfield">Don Banfield</name><name sortKey="Conrath, Barney J" sort="Conrath, Barney J" uniqKey="Conrath B" first="Barney J." last="Conrath">Barney J. Conrath</name><name sortKey="Gierasch, Peter J" sort="Gierasch, Peter J" uniqKey="Gierasch P" first="Peter J." last="Gierasch">Peter J. Gierasch</name><name sortKey="Matthews, Keith" sort="Matthews, Keith" uniqKey="Matthews K" first="Keith" last="Matthews">Keith Matthews</name><name sortKey="Nicholson, Philip D" sort="Nicholson, Philip D" uniqKey="Nicholson P" first="Philip D." last="Nicholson">Philip D. Nicholson</name><name sortKey="Squyres, Steven W" sort="Squyres, Steven W" uniqKey="Squyres S" first="Steven W." last="Squyres">Steven W. 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