Nonlinear tides in a homogeneous rotating planet or star: global modes and elliptical instabilityReportar como inadecuado


Nonlinear tides in a homogeneous rotating planet or star: global modes and elliptical instability


Nonlinear tides in a homogeneous rotating planet or star: global modes and elliptical instability - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Publication Date: 2016-03-28

Journal Title: Monthly Notices of the Royal Astronomical Society

Publisher: Oxford University Press

Language: English

Type: Article

Metadata: Show full item record

Citation: Barker, A. J., Braviner, H. J., & Ogilvie, G. I. (2016). Nonlinear tides in a homogeneous rotating planet or star: global modes and elliptical instability. Monthly Notices of the Royal Astronomical Society

Description: This is the author accepted manuscript. The final version is available from Oxford University Press via http://dx.doi.org/10.1093/mnras/stw701

Abstract: We revisit the global modes and instabilities of homogeneous rotating ellipsoidal fluid masses, which are the simplest global models of rotationally and tidally deformed gaseous planets or stars. The tidal flow in a short-period planet may be unstable to the elliptical instability, a hydrodynamic instability that can drive tidal evolution. We perform a global (and local WKB) analysis to study this instability using the elegant formalism of Lebovitz & Lifschitz. We survey the parameter space of global instabilities with harmonic orders ℓ ≤ 5, for planets with spins that are purely aligned (prograde) or anti-aligned (retrograde) with their orbits. In general, the instability has a much larger growth rate if the planetary spin and orbit are anti-aligned rather than aligned. We have identified a violent instability for anti-aligned spins outside of the usual frequency range for the elliptical instability (when n/Ω ≲ -1, where n and Ω are the orbital and spin angular frequencies, respectively) if the tidal amplitude is sufficiently large. We also explore the instability in a rigid ellipsoidal container, which is found to be quantitatively similar to that with a realistic free surface. Finally, we study the effect of rotation and tidal deformation on mode frequencies. We find that larger rotation rates and larger tidal deformations both decrease the frequencies of the prograde sectoral surface gravity modes. This increases the prospect of their tidal excitation, potentially enhancing the tidal response over expectations from linear theory. In a companion paper, we use our results to interpret global simulations of the elliptical instability.

Keywords: planetary systems, stars: rotation, binaries: close, hydrodynamics, waves, instabilities

Sponsorship: AJB is supported by the Leverhulme Trust and Isaac Newton Trust through the award of an Early Career Fellowship. The early stages of this research were supported by STFC through grants ST/J001570/1 and ST/L000636/1. HB was supported by a studentship funded by STFC and Trinity College, Cambridge. We would like to thank the referee, Jeremy Goodman, for several suggestions which have allowed us to improve the paper.

Identifiers:

This record's URL: http://dx.doi.org/10.1093/mnras/stw701https://www.repository.cam.ac.uk/handle/1810/254725





Autor: Barker, Adrian J.Braviner, Harry J.Ogilvie, Gordon I.

Fuente: https://www.repository.cam.ac.uk/handle/1810/254725



DESCARGAR PDF




Documentos relacionados