[mesa-users] Solid-body rotation in convective zones?

David Deschatelets david.deschatelets.1 at ulaval.ca
Wed Dec 4 01:17:30 EST 2013

Hello MESA users,

I've been analyzing for a while the effects of a Tayler-Spruit dynamo taking place within the radiative zone of a star.

The difference between a non-magnetic and magnetic simulation is easily observable and a near solid-body rotation can be seen in the radiative region due to angular momentum transport.

What took my attention on the evolution results is the angular velocity distribution in convective zones of the star (mostly when the star evolves away from the MS phase). I thought differential rotation was present in these regions (according to many papers I read) but what I'm observing is a constant angular velocity through the whole region.

This is well illustrated in Heger 2005 fig 1:  hhttp://m.iopscience.iop.org/0004-637X/626/1/350/fulltext/?providedHtml=61318.text.html

An explanation on this figure is: "In those regions large diffusion coefficients for angular momentum lead to nearly rigid rotation in all but the latest stages of the evolution", but I thought diffusion coefficients due to magnetic instability weren't present in such regions. Maybe are we talking here of another diffusion coefficient?

Is there a dynamo in the convection layer that is responsible for this?

Same phenomenon can be seen in the second MESA instrument paper fig 30: http://arxiv.org/pdf/1301.0319v2.pdf

This constant velocity in convective regions is present whether magnetic field is on or off.

Also, what is the reason for such rotation braking when going from radiative region to convective region (and then of course, why is the angular velocity being constant once the convective region is reached).

Thank you all for your answers.

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