A Coupled Thermal/Radiative Transfer Model Addressing the Infrared Emission of Saturn's Rings in Response to Radiative Forcing

Grant #: NNX08AN96G
Senior Scientist: Stuart Pilorz

This study continues the development of an existing thermal/radiative transfer model of Saturn’s rings [Pilorz et al., 2005]. The resulting model takes into account particle orbital motion, spin, ring particle size distribution and ring vertical profile in order to provide a more realistic model of optically thick rings such as Saturn’s A and B rings. The model consists of a radiative transfer (RT) code coupled with a thermal source term that is generated by a thermal model of individual ring particles. The model runs iteratively, and is self consistent in that the particles’ heating is driven by the computed radiance field, and their emission contributes to it.

Previously, no similarly complex model for Saturn’s rings had been developed.

 

The aim of this research is to incorporate into the RT code a 3-dimensional solution for heat flow within individual particles, which the PI has already developed. The new heat flow model replaces a phenomenological treatment currently in the radiative transfer model with a more realistic representation of heat flow within individual particles. This affects how the particles redirect flux absorbed from one direction into subsequent emission in other directions. Incorporating it requires a generalization from single particle response to forcing radiation to the response of ensembles of particles, in order to obtain a more realistic representation of an optically thick ring. With the combined code, we model thermal emission from the ring system, including the effects of particle spin distributions and realistic periodic radiation forcing, as seen by ring particles, and conduct sensitivity studies. This a study fills a key gap relating theoretical dynamical studies of rings to observational data, and is also important for understanding the thermal emission of disperse, particulate media in general.