scholarly journals Atmospheric thermal tides and planetary spin

2018 ◽  
Vol 609 ◽  
pp. A118 ◽  
Author(s):  
P. Auclair-Desrotour ◽  
S. Mathis ◽  
J. Laskar
Keyword(s):  
Rotation Frequency ◽  
Maxwell Model ◽  
Stable Stratification ◽  
Atmospheric Tides ◽  
Dissipated Energy ◽  
Tidal Dissipation ◽  
Tidal Torque ◽  
Tidal Waves ◽  
Tidally Driven ◽  
Thermal Tides

Context. Thermal atmospheric tides can torque telluric planets away from spin-orbit synchronous rotation, as observed in the case of Venus. They thus participate in determining the possible climates and general circulations of the atmospheres of these planets. Aims. The thermal tidal torque exerted on an atmosphere depends on its internal structure and rotation and on the tidal frequency. Particularly, it strongly varies with the convective stability of the entropy stratification. This dependence has to be characterized to constrain and predict the rotational properties of observed telluric exoplanets. Moreover, it is necessary to validate the approximations used in global modelings such as the traditional approximation, which is used to obtain separable solutions for tidal waves. Methods. We wrote the equations governing the dynamics of thermal tides in a local vertically stratified section of a rotating planetary atmosphere by taking into account the effects of the complete Coriolis acceleration on tidal waves. This allowed us to analytically derive the tidal torque and the tidally dissipated energy, which we used to discuss the possible regimes of tidal dissipation and to examine the key role played by stratification. Results. In agreement with early studies, we find that the frequency dependence of the thermal atmospheric tidal torque in the vicinity of synchronization can be approximated by a Maxwell model. This behavior corresponds to weakly stably stratified or convective fluid layers, as observed previously. A strong stable stratification allows gravity waves to propagate, and makes the tidal torque negligible. The transition is continuous between these two regimes. The traditional approximation appears to be valid in thin atmospheres and in regimes where the rotation frequency is dominated by the forcing or the buoyancy frequencies. Conclusions. Depending on the stability of their atmospheres with respect to convection, observed exoplanets can be tidally driven toward synchronous or asynchronous final rotation rates. The domain of applicability of the traditional approximation is rigorously constrained by calculations.

scholarly journals Tidal interactions in rotating multiple stars and their impact on their evolution

2014 ◽  
Vol 9 (S307) ◽  
pp. 208-210
Author(s):  
P. Auclair-Desrotour ◽  
S. Mathis ◽  
C. Le Poncin-Lafitte
Keyword(s):  
Fluid Model ◽  
Orbital Evolution ◽  
Tidal Dissipation ◽  
Tidal Waves ◽  
Physical Mechanisms ◽  
Tidal Interactions ◽  
The Earth ◽  
Half Height ◽  
Multiple Stars ◽  
Stellar Interiors

AbstractTidal dissipation in stars is one of the key physical mechanisms that drive the evolution of binary and multiple stars. As in the Earth oceans, it corresponds to the resonant excitation of their eigenmodes of oscillation and their damping. Therefore, it strongly depends on the internal structure, rotation, and dissipative mechanisms in each component. In this work, we present a local analytical modeling of tidal gravito-inertial waves excited in stellar convective and radiative regions respectively. This model allows us to understand in details the properties of the resonant tidal dissipation as a function of the excitation frequencies, the rotation, the stratification, and the viscous and thermal properties of the studied fluid regions. Then, the frequencies, height, width at half-height, and number of resonances as well as the non-resonant equilibrium tide are derived analytically in asymptotic regimes that are relevant in stellar interiors. Finally, we demonstrate how viscous dissipation of tidal waves leads to a strongly erratic orbital evolution in the case of a coplanar binary system. We characterize such a non-regular dynamics as a function of the height and width of resonances, which have been previously characterized thanks to our local fluid model.

Tidal dissipation modelling in gaseous giant planets at the time of space missions

2021 ◽  
Author(s):  
Hachem Dhouib ◽  
Stéphane Mathis ◽  
Florian Debras ◽  
Aurélie Astoul ◽  
Clément Baruteau
Keyword(s):  
Internal Structure ◽  
Differential Rotation ◽  
Giant Planets ◽  
Solid Core ◽  
Large Radius ◽  
Mixing Zone ◽  
Convective Envelope ◽  
Tidal Dissipation ◽  
Hot Jupiters ◽  
Tidal Waves

<p>Gaseous giant planets (Jupiter and Saturn in our solar system and hot Jupiters around other stars) are turbulent rotating magnetic objects that have strong and complex interactions with their environment (their moons in the case of Jupiter and Saturn and their host stars in the case of hot Jupiters/Saturns). In such systems, the dissipation of tidal waves excited by tidal forces shape the orbital architecture and the rotational dynamics of the planets.</p> <p>During the last decade, a revolution has occurred for our understanding of tides in these systems. First, Lainey et al. (2009, 2012, 2017) have measured tidal dissipation stronger by one order of magnitude than expected in Jupiter and Saturn. Second, unexplained broad diversity of orbital architectures and large radius of some hot Jupiters are observed in exoplanetary systems. Finally, new constraints obtained thanks to <em>Kepler</em>/K2 and TESS indicate that tidal dissipation in gaseous giant exoplanets is weaker than in Jupiter and in Saturn (Ogilvie 2014, Van Eylen et al. 2018, Huber et al. 2019).</p> <p>Furthermore, the space mission JUNO and the grand finale of the CASSINI mission have revolutionized our knowledge of the interiors of giant planets. We now know, for example, that Jupiter is a very complex planet: it is a stratified planet with, from the surface to the core, a differentially rotating convective envelope, a first mixing zone (with stratified convection), a uniformly rotating magnetised convective zone, a second magnetized mixing zone (the diluted core, potentially in stratified convection) and a solid core (Debras & Chabrier 2019). So far, tides in these planets have been studied by assuming a simplified internal structure with a stable rocky and icy core (Remus et al. 2012, 2015) and a deep convective envelope surrounded by a thin stable atmosphere (Ogilvie & Lin 2004) where mixing processes, differential rotation and magnetic field were completely neglected.</p> <p>Our objective is thus to predict tidal dissipation using internal structure models, which agree with these last observational constrains. In this work, we build a new ab-initio model of tidal dissipation in giant planets that coherently takes into account the interactions of tidal waves with their complex stratification induced by the mixing of heavy elements, their zonal winds, and (dynamo) magnetic fields. This model is a semi-global model in the planetary equatorial plane. We study the linear excitation of tidal magneto-gravito-inertial progressive waves and standing modes. We take into account the buoyancy, the compressibility, the Coriolis acceleration (including differential rotation), and the Lorentz force. The tidal waves are submitted to the different potential dissipative processes: Ohmic, thermal, molecular diffusivities, and viscosity. We here present the general formalism and the potential regimes of parameters that should be explored. The quantities of interest such as tidal torque, dissipation, and heating are derived. This will pave the way for full 3D numerical simulations that will take into account complex internal structure and dynamics of gaseous giant (exo-)planets in spherical/spheroidal geometry.</p> <p> </p>

scholarly journals Why do warm Neptunes present nonzero eccentricity?

2020 ◽  
Vol 635 ◽  
pp. A37 ◽  
Author(s):  
A. C. M. Correia ◽  
V. Bourrier ◽  
J.-B. Delisle
Keyword(s):  
Planetary Systems ◽  
Atmospheric Tides ◽  
Tidal Dissipation ◽  
Bodily Tides ◽  
Orbital Periods

Most Neptune-mass planets in close-in orbits (orbital periods less than a few days) present nonzero eccentricity, typically around 0.15. This is somehow unexpected, as these planets undergo strong tidal dissipation that should circularize their orbits in a timescale shorter than the age of the system. In this paper we discuss some mechanisms that can oppose to bodily tides, namely, thermal atmospheric tides, evaporation of the atmosphere, and excitation from a distant companion. In the first two cases, the eccentricity can increase consistently, while in the last one, the eccentricity can only be excited for a limited amount of time (that may nevertheless exceed the age of the system). We show the limitations of these different mechanisms and how some of them could, depending on specific properties of the observed planetary systems, account for their presently observed eccentricities.

scholarly journals Thermal tides in rotating hot Jupiters

2019 ◽  
Vol 488 (2) ◽  
pp. 1960-1976 ◽  
Author(s):  
Umin Lee ◽  
Daiki Murakami
Keyword(s):  
Harmonic Functions ◽  
Series Expansions ◽  
Radiative Cooling ◽  
Tidal Torque ◽  
Hot Jupiters ◽  
The Core ◽  
Oscillation Modes ◽  
Convective Core ◽  
Thermal Tides ◽  
Spherical Harmonic Functions

ABSTRACT We calculate tidal torque due to semidiurnal thermal tides in rotating hot Jupiters, taking account of the effects of radiative cooling in the envelope and of the planets rotation on the tidal responses. We use a simple Jovian model composed of a nearly isentropic convective core and a thin radiative envelope. To represent the tidal responses of rotating planets, we employ series expansions in terms of spherical harmonic functions $Y_l^m$ with different ls for a given m. For low-forcing frequency, there occurs frequency resonance between the forcing and the g- and r-modes in the envelope and inertial modes in the core. We find that the resonance enhances the tidal torque, and that the resonance with the g- and r-modes produces broad peaks and that with the inertial modes very sharp peaks, depending on the magnitude of the non-adiabatic effects associated with the oscillation modes. We also find that the behaviour of the tidal torque as a function of the forcing frequency (or period) is different between prograde and retrograde forcing, particularly for long forcing periods because the r-modes, which have long periods, exist only on the retrograde side.

scholarly journals Oceanic tides from Earth-like to ocean planets

2018 ◽  
Vol 615 ◽  
pp. A23 ◽  
Author(s):  
P. Auclair-Desrotour ◽  
S. Mathis ◽  
J. Laskar ◽  
J. Leconte
Keyword(s):  
Gravity Waves ◽  
Three Dimensional ◽  
Stable Stratification ◽  
Internal Gravity Waves ◽  
Tidal Dissipation ◽  
Planetary Rotation ◽  
Wide Range ◽  
Oceanic Tides ◽  
3D Effects ◽  
Tidal Response

Context. Oceanic tides are a major source of tidal dissipation. They drive the evolution of planetary systems and the rotational dynamics of planets. However, two-dimensional (2D) models commonly used for the Earth cannot be applied to extrasolar telluric planets hosting potentially deep oceans because they ignore the three-dimensional (3D) effects related to the ocean’s vertical structure. Aims. Our goal is to investigate, in a consistant way, the importance of the contribution of internal gravity waves in the oceanic tidal response and to propose a modelling that allows one to treat a wide range of cases from shallow to deep oceans. Methods. A 3D ab initio model is developed to study the dynamics of a global planetary ocean. This model takes into account compressibility, stratification, and sphericity terms, which are usually ignored in 2D approaches. An analytic solution is computed and used to study the dependence of the tidal response on the tidal frequency and on the ocean depth and stratification. Results. In the 2D asymptotic limit, we recover the frequency-resonant behaviour due to surface inertial-gravity waves identified by early studies. As the ocean depth and Brunt–Väisälä frequency increase, the contribution of internal gravity waves grows in importance and the tidal response becomes 3D. In the case of deep oceans, the stable stratification induces resonances that can increase the tidal dissipation rate by several orders of magnitude. It is thus able to significantly affect the evolution time scale of the planetary rotation.

scholarly journals Seasonal variability of atmospheric tides in the mesosphere and lower thermosphere: meteor radar data and simulations

2018 ◽  
Vol 36 (3) ◽  
pp. 825-830 ◽  
Author(s):  
Dimitry Pokhotelov ◽  
Erich Becker ◽  
Gunter Stober ◽  
Jorge L. Chau
Keyword(s):  
Seasonal Variability ◽  
Lower Thermosphere ◽  
Circulation Model ◽  
Radar Data ◽  
Atmospheric Tides ◽  
Northern Germany ◽  
Model Driven ◽  
Resolution Model ◽  
Mesosphere And Lower Thermosphere ◽  
Thermal Tides

Abstract. Thermal tides play an important role in the global atmospheric dynamics and provide a key mechanism for the forcing of thermosphere–ionosphere dynamics from below. A method for extracting tidal contributions, based on the adaptive filtering, is applied to analyse multi-year observations of mesospheric winds from ground-based meteor radars located in northern Germany and Norway. The observed seasonal variability of tides is compared to simulations with the Kühlungsborn Mechanistic Circulation Model (KMCM). It is demonstrated that the model provides reasonable representation of the tidal amplitudes, though substantial differences from observations are also noticed. The limitations of applying a conventionally coarse-resolution model in combination with parametrisation of gravity waves are discussed. The work is aimed towards the development of an ionospheric model driven by the dynamics of the KMCM.

scholarly journals Scaling laws to understand tidal dissipation in fluid planetary layers and stars

2014 ◽  
Vol 9 (S310) ◽  
pp. 29-32
Author(s):  
Pierre Auclair-Desrotour ◽  
Stéphane Mathis ◽  
Christophe Le Poncin-Lafitte
Keyword(s):  
Thermal Diffusivity ◽  
Scaling Laws ◽  
Planetary Systems ◽  
Viscous Friction ◽  
Local Model ◽  
Tidal Dissipation ◽  
Tidal Waves ◽  
Secular Evolution ◽  
Structure And Dynamics ◽  
Internal Parameters

AbstractTidal dissipation is known as one of the main drivers of the secular evolution of planetary systems. It directly results from dissipative mechanisms that occur in planets and stars' interiors and strongly depends on the structure and dynamics of the bodies. This work focuses on the mechanism of viscous friction in stars and planetary layers. A local model is used to study tidal dissipation. It provides general scaling laws that give a qualitative overview of the different possible behaviors of fluid tidal waves. Furthermore, it highlights the sensitivity of dissipation to the tidal frequency and the roles played by the internal parameters of the fluid such as rotation, stratification, viscosity and thermal diffusivity that will impact the spins/orbital architecture in planetary systems.

scholarly journals Layered semi-convection and tides in giant planet interiors

2019 ◽  
Vol 626 ◽  
pp. A82 ◽  
Author(s):  
Q. André ◽  
S. Mathis ◽  
A. J. Barker
Keyword(s):  
Large Fraction ◽  
Giant Planet ◽  
Vertical Direction ◽  
Thermal Dissipation ◽  
Free Boundaries ◽  
Compositional Gradient ◽  
Tidal Dissipation ◽  
Hot Jupiters ◽  
Tidal Waves ◽  
Dissipation Rates

Context. Recent Juno observations have suggested that the heavy elements in Jupiter could be diluted throughout a large fraction of its gaseous envelope, providing a stabilising compositional gradient over an extended region of the planet. This could trigger layered semi-convection, which, in the context of giant planets more generally, may explain Saturn’s luminosity excess and play a role in causing the abnormally large radii of some hot Jupiters. In giant planet interiors, it could take the form of density staircases, which are convective layers separated by thin stably stratified interfaces. In addition, the efficiency of tidal dissipation is known to depend strongly on the planetary internal structure. Aims. We aim to study the resulting tidal dissipation when internal waves are excited in a region of layered semi-convection by tidal gravitational forcing due to other bodies (such as moons in giant planet systems, or stars in hot Jupiter systems). Methods. We adopt a local Cartesian model with a background layered density profile subjected to an imposed tidal forcing, and we compute the viscous and thermal dissipation rates numerically. We consider two sets of boundary conditions in the vertical direction: periodic boundaries and impenetrable, stress-free boundaries, with periodic conditions in the horizontal directions in each case. These models are appropriate for studying the forcing of short-wavelength tidal waves in part of a region of layered semi-convection, and in an extended envelope containing layered semi-convection, respectively. Results. We find that the rates of tidal dissipation can be enhanced in a region of layered semi-convection compared to a uniformly convective medium, where the latter corresponds with the usual assumption adopted in giant planet interior models. In particular, a region of layered semi-convection possesses a richer set of resonances, allowing enhanced dissipation for a wider range of tidal frequencies. The details of these results significantly depend on the structural properties of the layered semi-convective regions. Conclusions. Layered semi-convection could contribute towards explaining the high tidal dissipation rates observed in Jupiter and Saturn, which have not yet been fully explained by theory. Further work is required to explore the efficiency of this mechanism in global models.

scholarly journals A Simplified Model for a Nonlinear Tidal Effect on Accretion Disks in CVS

1993 ◽  
Vol 134 ◽  
pp. 371-371
Author(s):  
Zhong-Yong Zhang ◽  
Jian-Sheng Chen
Keyword(s):  
Numerical Simulation ◽  
Accretion Disk ◽  
Accretion Disks ◽  
Dissipation Function ◽  
Tidal Effect ◽  
Simplified Model ◽  
Two Dimensional ◽  
Tidal Dissipation ◽  
Tidal Torque ◽  
Dwarf Nova

AbstractThis paper investigates the tidal effect on accretion disk in CVs and sets up a simplified model in which the secondary’s gravitation is substituted by a mean tidal torque. We find that a linear tidal torque will not be able to maintain an equilibrium disk. By using the result of the radius of the equilibrium disk approximately equals to the tidal radius, which was obtained by using the two dimensional numerical simulation invoking nonlinear tidal effect, we give the modified tidal dissipation function for our simplified model which could be used to interpret the outburst of the dwarf nova with tidal effect. The paper also shows that the radius of an equilibrium disk with a torus is slightly small than the Lubow-Shu radius, and the tidal effect may also cause the cycle of quiescence-superoutburst in addition to the cycle of quiescence-outbursts-superoutburst.

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