Interpreting the librations of a synchronous satellite – How their phase assesses Mimas’ global ocean

Noyelles, Benoît

doi:10.1016/j.icarus.2016.10.001

Cited by 19 publications

(21 citation statements)

References 39 publications

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“…which coincides with the result obtained by Van Hoolst et al (2013). This expression is compared with other results in literature by Noyelles (2017). The classical formula for the amplitude of forced libration of a rigid triaxial body under the same circumstances is (Danby (1962) also Efroimsky (2018a) equation (13) or Thomas et al (2016) equation (1))…”

Section: Amplitude Of Forced Libration: Comparison With Other Resultssupporting

confidence: 86%

Andrade rheology in time-domain. Application to Enceladus' dissipation of energy due to forced libration

Gevorgyan

Boué

Ragazzo

et al. 2020

Icarus

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The main purpose of this work is to present a time-domain implementation of the Andrade rheology, instead of the traditional expansion in terms of a Fourier series of the tidal potential. This approach can be used in any fully three dimensional numerical simulation of the dynamics of a system of many deformable bodies. In particular, it allows large eccentricities, large mutual inclinations, and it is not limited to quasi-periodic perturbations. It can take into account an extended class of perturbations, such as chaotic motions, transient events, and resonant librations.The results are presented by means of a concrete application: the analysis of the libration of Enceladus. This is done by means of both analytic formulas in the frequency domain and direct numerical simulations. We do not a priori assume that Enceladus has a triaxial shape, the eventual triaxiality is a consequence of the satellite motion and its rheology. As a result we obtain an analytic formula for the amplitude of libration that incorporates a new correction due to the rheology.Our results provide an estimation of the amplitude of libration of the core of Enceladus as 0.6% of that of the shell. They also reproduce the observed 10 GW of tidal heat generated by Enceladus with a value of 0.17 × 10 14 Pa·s for the global effective viscosity under both Maxwell and Andrade rheology.

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Section: Amplitude Of Forced Libration: Comparison With Other Resultssupporting

confidence: 86%

Andrade rheology in time-domain. Application to Enceladus' dissipation of energy due to forced libration

Gevorgyan

Boué

Ragazzo

et al. 2020

Icarus

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“…= 42.1 km/Myr; thus, Tethys may be decelerating Mimas' orbital migration, and if the latter has been caught in the resonance since its formation, the migration time-scale would then be slightly larger. However, recent studies of Mimas suggest that it may possess a global subsurface ocean (Tajeddine et al 2014, Noyelles et al 2016, Noyelles 2017, Caudal 2017, although such a claim is difficult to reconcile with the absence of surface fracturing (Rhoden et al 2017). If this is true, orbital migration could have been delayed recently by tidal dissipation in the satellite, thus increasing the estimated age.…”

Section: Evolution Of the Satellites Of Saturnmentioning

confidence: 99%

What Confines the Rings of Saturn?

Tajeddine

Nicholson

Longaretti

et al. 2017

ApJS

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The viscous spreading of planetary rings is believed to be counteracted by satellite torques, either through an individual resonance or through overlapping resonances. For the A ring of Saturn, it has been commonly believed that the satellite Janus alone can prevent the ring from spreading via its 7:6 Lindblad resonance. We discuss this common misconception and show that, in reality, the A ring is confined by the contributions from the group of satellites Pan, Atlas, Prometheus, Pandora, Janus, Epimetheus, and Mimas, whose cumulative torques from various resonances gradually decrease the angular momentum flux transported outward through the ring via density and bending waves. We further argue that this decrease in angular momentum flux occurs through 'flux reversal'. Furthermore, we use the magnitude of the satellites' resonance torques to estimate the effective viscosity profile across the A ring, showing that it decreases with radius from ~50 cm 2 s -1 to less than ~10 cm 2 s -1 . The gradual estimated decrease of the angular momentum flux and effective viscosity are roughly consistent with results obtained by balancing the shepherding torques from Pan and Daphnis with the viscous torque at the edges of the Encke and Keeler gaps, as well as the edge of the A ring.On the other hand, the Mimas 2:1 Lindblad resonance alone seems to be capable of confining the edge of the B ring, and contrary to the situation in the A ring, we show that the effective viscosity across the B ring is relatively constant at ~24-30 cm 2 s -1 .

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“…A model of the type (32) has been used in the past (see [15] and references therein) to describe a spacecraft with flexible components. A similar approach is also used in [19], where the elements of the tensor of inertia are expressed as the sum of a frozen (constant) and a hydrostatic (time-varying) component. The differential equation describing the rotation isθ…”

Section: Applicationsmentioning

confidence: 99%

Hamiltonian formulation of the spin-orbit model with time-varying non-conservative forces

Gkolias

Efthymiopoulos

Pucacco

et al. 2017

Communications in Nonlinear Science and Numerical Simulation

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Abstract. In a realistic scenario, the evolution of the rotational dynamics of a celestial or artificial body is subject to dissipative effects. Time-varying non-conservative forces can be due to, for example, a variation of the moments of inertia or to tidal interactions. In this work, we consider a simplified model describing the rotational dynamics, known as the spin-orbit problem, where we assume that the orbital motion is provided by a fixed Keplerian ellipse. We consider different examples in which a non-conservative force acts on the model and we propose an analytical method, which reduces the system to a Hamiltonian framework. In particular, we compute a time parametrisation in a series form, which allows us to transform the original system into a Hamiltonian one. We also provide applications of our method to study the rotational motion of a body with time-varying moments of inertia, e.g. an artificial satellite with flexible components, as well as subject to a tidal torque depending linearly on the velocity.

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Interpreting the librations of a synchronous satellite – How their phase assesses Mimas’ global ocean

Cited by 19 publications

References 39 publications

Andrade rheology in time-domain. Application to Enceladus' dissipation of energy due to forced libration

Andrade rheology in time-domain. Application to Enceladus' dissipation of energy due to forced libration

What Confines the Rings of Saturn?

Hamiltonian formulation of the spin-orbit model with time-varying non-conservative forces

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