Effect of Rossby and Alfvén waves on the dynamics of the tachocline

Abstract

To understand magnetic diffusion, momentum transport, and mixing in the interior of the sun, we consider an idealized model of the tachocline, namely magnetohydrodynamics (MHD) turbulence on a $\beta$ plane subject to a large scale shear (provided by the latitudinal differential rotation). This model enables us to self-consistently derive the influence of shear, Rossby and Alfvén waves on the transport properties of turbulence. In the strong magnetic field regime, we find that the turbulent viscosity and diffusivity are reduced by magnetic fields only, similarly to the two-dimensional MHD case (without Rossby waves). In the weak magnetic field regime, we find a crossover scale ($L\_R$) from a Alfvén dominated regime (on small scales) to a Rossby dominated regime (on large scales). For parameter values typical of the tachocline, $L\_R$ is larger that the solar radius so that Rossby waves are unlikely to play an important role in the transport of magnetic field and angular momentum. This is mainly due to the enhancement of magnetic back-reaction by shearing which efficiently generates small scales, thus strong currents.

References in corpus (1)

• Self-consistent theory of turbulent transport in the solar tachocline. II. Tachocline confinement

Cited by in corpus (9)

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• Effect of rotation on the tachoclinic transport
• Potential Vorticity Transport in Weakly and Strongly Magnetized Plasmas
• Analytical theory of forced rotating sheared turbulence. I. Perpendicular case
• Analytical theory of forced rotating sheared turbulence. The Parallel case
• Resonance enhanced turbulent transport
• Multi-scale theory of rotating turbulence