Empirical Structure Models of Uranus and Neptune

Abstract

Uranus and Neptune are still poorly understood. Their gravitational fields, rotation periods, atmosphere dynamics, and internal structures are not well determined. In this paper we present empirical structure models of Uranus and Neptune where the density profiles are represented by polytropes. By using these models, that are set to fit the planetary gravity field, we predict the higher order gravitational coefficients $J_6$ and $J_8$ for various assumed rotation periods, wind depths, and uncertainty of the low-order harmonics. We show that faster rotation and/or deep winds favour centrally concentrated density distributions. We demonstrate that an accurate determination of $J_6$ or $J_8$ with a relative uncertainty no larger than $10\%$ could constrain wind depths of Uranus and Neptune. We also confirm that the Voyager rotation periods are inconsistent with the measured shapes of Uranus and Neptune. We next demonstrate that more accurate determination of the gravity field can significantly reduce the possible range of internal structures. Finally, we suggest that an accurate measurement of the moment of inertia of Uranus and Neptune with a relative uncertainty of $\sim 1\%$ and $\sim 0.1\%$, could constrain their rotation periods and depths of the winds, respectively.

14 pages, 12 figures, 2 tables, accepted for publication in MNRAS

References in corpus (6)

• Thermal evolution of Uranus and Neptune I: adiabatic models
• Low- and high-order gravitational harmonics of rigidly rotating Jupiter
• Properties of hydrogen, helium, and silicon dioxide mixtures in giant planet interiors
• Constraining the Depth of the Winds on Uranus and Neptune via Ohmic Dissipation
• Orbits and resonances of the regular moons of Neptune
• Connecting gravity field, moment of inertia, and core properties in Jupiter through empirical structure models

Cited by in corpus (1)

• One EURO for Uranus: the Elliptical Uranian Relativity Orbiter mission