Transient F Ring Dust Features in Cassini UVIS Solar Occultations

Abstract:

We present results from an investigation of the variable particle size distribution in Saturn’s dynamic F ring. We analyze 13 solar occultations observed by the Cassini Ultraviolet Imaging Spectrograph (UVIS), of which 4 occultations show a clear signature of diffracted sunlight. The magnitude and scattering angle of the diffraction signal suggest the presence of a significant population of micron-sized dust particles; however, the lack of a detection of diffracted light in other solar occultations implies that such a population is transient or spatially variable. Initial comparisons with images from the Cassini Imaging Science Subsystem (ISS) suggest that a diffraction signal is detected in UVIS occultations that coincide with a recent collisional event in the F ring core, as seen in the ISS images. This implies that such events release a significant population of dust, which can then be measured by the diffraction signature in the UVIS data. We use a forward-modeling approach to place constraints on the particle size distribution of the F ring during each solar occultation. We present these measurements of the size distribution and our comparisons of the F ring dust population as measured by UVIS with the ISS images of the ring.