Antisolar differential rotation of slowly rotating cool stars. (arXiv:1902.04172v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Rudiger_G/0/1/0/all/0/1">G. Rüdiger</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kuker_M/0/1/0/all/0/1">M. Küker</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kapyla_P/0/1/0/all/0/1">P. Käpylä</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Strassmeier_K/0/1/0/all/0/1">K.G. Strassmeier</a>
It is well-known that rotating stellar convection transports angular momentum
equatorward while a thermal energy flows poleward producing warm poles. The
characteristic equatorial acceleration of the solar rotation law is a
consequence of these phenomena. New numerical box simulations confirm the cross
correlations $langle u_r u_thetarangle $ and $langle u_theta u_phirangle
$ to be anticorrelated but their signs prove to be different for slow and fast
rotation. The explanation is that for slow rotation large-scale circulation
patterns appear which via viscosity terms change the signs of the cross
correlations which transport angular momentum toward the poles and heat toward
the equator. A so far neglected rotation-induced off-diagonal eddy viscosity
term in connection with rotation laws with negative radial gradient, therefore,
causes antisolar rotation laws with decelerated equator. The observation of
decelerated equators at slowly rotating stars would thus lead to a better
understanding of the active eddy viscosity tensor and the underlying
turbulence.
It is well-known that rotating stellar convection transports angular momentum
equatorward while a thermal energy flows poleward producing warm poles. The
characteristic equatorial acceleration of the solar rotation law is a
consequence of these phenomena. New numerical box simulations confirm the cross
correlations $langle u_r u_thetarangle $ and $langle u_theta u_phirangle
$ to be anticorrelated but their signs prove to be different for slow and fast
rotation. The explanation is that for slow rotation large-scale circulation
patterns appear which via viscosity terms change the signs of the cross
correlations which transport angular momentum toward the poles and heat toward
the equator. A so far neglected rotation-induced off-diagonal eddy viscosity
term in connection with rotation laws with negative radial gradient, therefore,
causes antisolar rotation laws with decelerated equator. The observation of
decelerated equators at slowly rotating stars would thus lead to a better
understanding of the active eddy viscosity tensor and the underlying
turbulence.
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