HR: 1340h
AN: P43B-1296    [Abstracts]
TI: Characterization of Enigmatic Saturn's Ring B by Cassini Radio Occultations
AU: * Marouf, E A
EM: emarouf@email.sjsu.edu
AF: San Jose State University, Department of Electrical Engineering, San Jose, CA 95192- 0084, United States
AU: French, R G
EM: rfrench@wellesley.edu
AF: Wellesley College, Department of Astronomy, Wellesley, MA 02481, United States
AU: Rappaprt, N J
EM: Nicole.J.Rappaport@jpl.nasa.gov
AF: Caltech/JPL, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AU: McGhee, C A
EM: cmcghee@wellesley.edu
AF: Wellesley College, Department of Astronomy, Wellesley, MA 02481, United States
AU: Thomson, F S
EM: fthomson@stanford.edu
AF: Stanford University, Department of Electrical Engineering, Stanford, CA 94301, United States
AU: Wong, K
EM: wong_inbox@yahoo.com
AF: San Jose State University, Department of Electrical Engineering, San Jose, CA 95192- 0084, United States
AU: Anabtawi, A
EM: Aseel.Anabtawi@jpl.nasa.gov
AF: Caltech/JPL, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AB: Cassini radio occultation observations of the extinction and near-forward scattering of 0.94, 3.6, and 13 cm- wavelengths sinusoidal signals have shed much new light on the structure and physical properties of Saturn's main ring system, especially enigmatic Ring B. As of June 2007, the occultations covered 15 distinct ring longitudes and roughly two distinct ranges of ring opening angle B; the first 12 covered B = 19.5-23.5 deg, and the last three B =14-15 deg. Four sub-regions of Ring B, identified as B1 to B4 (bounded by rough ring radius = 92, 99, 104.5, 110, 117.5 thousand km) exhibit clearly distinct structure (Marouf et al., 38th DPS Meeting, 38.05, 2006). Region B2, in particular, is characterized by remarkable 'bi-stable' states, where the optical depth abruptly flip-flops between optical depth of about 2 and more than 5. We consider observational evidence that bear on physical characterization of the observed structure (particle sizes, particle-cluster-sizes and orientation, spatial cluster density, vertical ring profile and physical thickness, ...). On the signal extinction side, this includes differential extinction of the three radio signals, and apparent variation of optical depth with observation longitude and ring opening angle (azimuthal asymmetry). On the forward scattered signal side, it includes strength, bandwidth, spectral shape and Doppler drift-rate of observed spectrogram features. We present representative results for selected features in regions B1, B2, and B4. Of particular interest is the detection of quasi-periodic ring structure of period roughly 100 meters in region B2 (and perhaps B4). In contrast with the prevalent gravitational wakes, the periodic structure is not azimuthally inclined and appears to be an independent structure superposed on the background wake structure (Thomson et al., submitted 2007).
DE: 6265 Planetary rings
DE: 6964 Radio wave propagation
DE: 6969 Remote sensing
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting