A critical review on the dynamics of Jovian atmospheres

Yano, Jun–Ichi

doi:10.1063/1.166008

Cited by 14 publications

(9 citation statements)

References 95 publications

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“…In particular, we wish to address the possibility of an origin of these structures in deep layers, where the fluid is electrically conducting (metallic hydrogen), and therefore influenced by the presence of a magnetic field (Yano 1994, Aurnou and Olson 2001, Christensen 2002, Morin and Dormy 2005. Numerical simulations of convection (Heimpel et al 2005) show that the zonal wind resembles the banded structure of Jupiter and Saturn for high enough Rayleigh numbers.…”

Section: Applications To Jupitermentioning

confidence: 99%

Two-dimensional non-linear simulations of the magnetostrophic magnetorotational instability

Petitdemange

2010

Geophysical & Astrophysical Fluid Dynamics

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We have shown that a simple, modified version of the Magnetorotational Instability (MRI) can, in principle, develop in the Earth's outer liquid core in the presence of a background shear (see Petitdemange, Dormy and Balbus, MagnetoStrophic MRI in the Earth's outer core. Geophys. Res. Lett. 2008, 35 15305). We refer to this instability as the Magnetostrophic MRI (MS-MRI). In this article, we extend our investigations to the nonlinear regime and present results from global axisymmetric simulations in spherical geometry. We show that as the angular momentum is transported outward, the MS-MRI saturates by rapidly changing the initial shear profile. Therefore, the saturation process differs substantially from traditional MRI applications (e.g. accretion disks) in which the background shear is essentially fixed. We show that the MS-MRI appears as a new constraint which limits the maximum differential rotation. To illustrate this mechanism, we apply this work to a Jupiter-like planet, and argue that the magnetic field eventually destabilises the conducting zone of this planet. According to these results, purely hydrodynamic models for the deep origin of the banded structure of Jupiter may need to be modified.

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Section: Applications To Jupitermentioning

confidence: 99%

Two-dimensional non-linear simulations of the magnetostrophic magnetorotational instability

Petitdemange

2010

Geophysical & Astrophysical Fluid Dynamics

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“…Vasavada and Showman (2005) point out that such a deep rooted superrotation underlying a shallow atmosphere can explain the near, but imperfect, symmetry between northern and southern hemispheres. In this respect as pointed by Yano (1994) the coupling of deep thermal convection with the atmospheric circulation is the next step for modeling.…”

Section: Discussion: Shallow Vs Deep Approachesmentioning

confidence: 99%

Turbulent convection in an anelastic rotating sphere : a model for the circulation on the giant planets

Kaspi¹

2008

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This thesis studies the dynamics of a rotating compressible gas sphere, driven by internal convection, as a model for the dynamics on the giant planets. We develop a new general circulation model for the Jovian atmosphere, based on the MITgcm dynamical core augmenting the nonhydrostatic model. The grid extends deep into the planet's interior allowing the model to compute the dynamics of a whole sphere of gas rather than a spherical shell (including the strong variations in gravity and the equation of state). Dierent from most previous 3D convection models, this model is anelastic rather than Boussinesq and thereby incorporates the full density variation of the planet.We show that the density gradients caused by convection drive the system away from an isentropic and therefore barotropic state as previously assumed, leading to signicant baroclinic shear. This shear is concentrated mainly in the upper levels and associated with baroclinic compressibility eects. The interior ow organizes in large cyclonically rotating columnar eddies parallel to the rotation axis, which drive upgradient angular momentum eddy uxes, generating the observed equatorial superrotation. Heat uxes align with the axis of rotation, contributing to the observed at meridional emission. We show the transition from weak convection cases with symmetric spiraling columnar modes similar to those found in previous analytic linear theory, to more turbulent cases which exhibit similar, though less regular and solely cyclonic, convection columns which manifest on the surface in the form of waves embedded within the superrotation. We develop a mechanical understanding of this system and scaling laws by studying simpler congurations and the dependence on physical properties such as the rotation period, bottom boundary location and forcing structure.These columnar cyclonic structures propagate eastward, driven by dynamics similar to that of a Rossby wave except that the restoring planetary vorticity gradient 3 is in the opposite direction, due to the spherical geometry in the interior. We further study these interior dynamics using a simplied barotropic annulus model, which shows that the planetary vorticity radial variation causes the eddy angular momentum ux divergence, which drives the superrotating equatorial ow. In addition we study the interaction of the interior dynamics with a stable exterior weather layer, using a quasigeostrophic two layer channel model on a beta plane, where the columnar interior is therefore represented by a negative beta eect. We nd that baroclinic instability of even a weak shear can drive strong, stable multiple zonal jets. For this model we nd an analytic nonlinear solution, truncated to one growing mode, that exhibits a multiple jet meridional structure, driven by the nonlinear interaction between the eddies. Finally, given the density eld from our 3D convection model we derive the high order gravitational spectra of Jupiter, which is a measurable quantity for the upcoming JUNO mission to Jupiter. Glenn Flierl, my...

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“…Deep convection models producing bands in the sphere are limited so far to a moderate number of bands per hemisphere. 3,[13][14][15][16][17][18] Investigation of decaying turbulence in a full sphere 18 has allowed more importance to be given to nonlinearities and also revealed the presence of a banded structure. The possible deep origin of bands in giant planets therefore remains a much debated topic.…”

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confidence: 99%

Dissipation mechanisms for convection in rapidly rotating spheres and the formation of banded structures

Morin

Dormy

2006

Physics of Fluids

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We report banded zonal structures in numerical simulations of weakly nonlinear rapidly rotating convection. A quasigeostrophic model of convection is used to demonstrate how, in the presence of Ekman pumping, banded structures can develop immediately above the onset of convection, and in the absence of developed turbulence. We argue that these bands necessarily correspond to a regime in which both Ekman pumping and bulk viscosity equally affect the zonal flow and that their width scales with the Ekman number E as E 1/4 . We investigate the respective role of two dissipation mechanisms, bulk viscosity and Ekman friction, acting on weakly nonlinear rapidly rotating convection. To make the problem tractable in a parameter regime of small Ekman numbers ͑low viscosity͒, we use a simplified approach relying on a z-integrated set of equations ͑known as quasigeostrophic convection, or ␤ convection 1 ͒. In a previous investigation using a similar approach, 2 we have shown, in the presence of bulk viscosity only, that as the Ekman number is decreased toward realistic values ͑which are presently out of reach of fully three-dimensional modeling͒ the zonal flow becomes increasingly important near the onset of convection. We have shown that, from an asymptotic point of view, the zonal flow is strong enough to suppress convective motions on a quasiperiodic basis and to yield relaxation oscillations immediately above the onset. 2 In all studies of quasigeostrophic or fully threedimensional convection, when only bulk viscosity is retained, the zonal flow near onset takes the form of a large "S" structure in the radius, with two counter-rotating bands ͑retrograde near the axis and prograde near the equator͒. As the Rayleigh number is further increased above critical, the number of bands slowly increases. 3 Recently, Jones et al. 4 investigated the effect of dissipation in the viscous boundary layers. They used a twodimensional rotating annulus model with mixed mechanical boundary conditions. Their model is strongly nonlinear and relies on a prescribed radial variation of the stream function. Introducing the effect of Ekman pumping, they were able to achieve a significantly higher number of bands ͑up to six on the ␤ plan͒ for a given Rayleigh number. The role of Ekman pumping in producing these jets still needs to be clarified, as well as the resulting balance between dissipation mechanisms. This turbulent approach differs from the weakly nonlinear investigation presented here.The zonal flow is driven by nonlinearities. Independent of which dissipation mechanism affects the axisymmetric component of the flow, its radial profile exhibits prograde and retrograde velocities. It is the shearing action of the zonal flow on the convective columns which yields the kinetic energy saturation. The zonal flow has to produce a strong enough shear to saturate the growth of convective motions. If only bulk viscosity is retained in the zonal flow equation, this shear will be achieved while minimizing the second derivative of the zonal velocity in...

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A critical review on the dynamics of Jovian atmospheres

Cited by 14 publications

References 95 publications

Two-dimensional non-linear simulations of the magnetostrophic magnetorotational instability

Two-dimensional non-linear simulations of the magnetostrophic magnetorotational instability

Turbulent convection in an anelastic rotating sphere : a model for the circulation on the giant planets

Dissipation mechanisms for convection in rapidly rotating spheres and the formation of banded structures

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