Toward constraining Saturn's rotation rate by interior modeling

Abstract

The rotation rate of the outer planet Saturn is not well constrained by classical measurements of periodic signals. Recent and diverse approaches using a broad spectrum of Cassini and other observational data related to shape, winds, and oscillations are converging toward a value about 6 to 7 minutes faster than the Voyager rotation period. Here we present our method of using zonal wind data and the even harmonics J2 to J10 measured during the Cassini Grand Finale tour to infer the deep rotation rate of Saturn. We assume differential rotation on cylinders and generate adiabatic density profiles that match the low-order J2 and J4 values. Theory of Figures to 7th order is applied to estimate the differences in the high-order moments J6 to J10 that may result from the winds and the assumed reference rotation rate. Presented results are preliminary as the method is under construction.