CHARACTERISTIC WAVELENGTHS OF IRREGULAR STRUCTURE IN SATURNS B-RING

We have analyzed the spatial structure in Saturn's B and A rings for r egional variations in characteristic spatial scales. To do this, we ob tained radial scans of the reflectivity of the rings from the highest resolution full radial scan of the lit face of the rings in the Voyage r image data set. The images were obtained in the Voyager 2 narrow ang le camera, clear filter and have a resolution of approximately 5 km/pi xel in the radial direction (the scans are slightly oversampled to 3.5 km). The radial scans were analyzed using a Burg maximum entropy tech nique to obtain spatial frequency spectra as a function of radial loca tion in the B ring, Comparisons were made of the Burg technique and FF T techniques, and estimates of the limitations of the method were made . We find that the main rings display characteristic structure on seve ral scales that vary with location. In the inner B ring (between the i nner edge and around 99,000 km), a characteristic scale of 80-100 km i s found. Between 99,000 and 103,500 ion, the 80-100 km scale vanishes and a strong preference for a longer wavelength (200-300 km) is seen. In this region, finer scale structure (20-40 km scale) is seen in abun dance. This scale structure is absent in the inner B ring. The region between 103,500 and 116,000 ion has a very strong preference for 200-3 00 km scale structure and is practically devoid of fine scale structur e except for a handful of isolated bursts. None of these bursts corres pond to known strong resonances, Outside of 116,000 km, fine scale str ucture again appears in abundance, on top of the 200-300 km scale, and covers the ring to its outer edge. The Mimas 4:2 bending wave is clea rly seen, but is responsible for only a very small fraction of the obs erved fine structure. (C) 1996 Academic Press, Inc.