[mesa-users] dynamo effect on stellar str

[Valery Pipin]

Dear Brian,

Thanks for the  paper! Indeed, the magnetic field  perturbs the 
hydrostatic balance and the background thermodynamics  as well as the 
global rotation does.
However, the most strong perturbations of those balances are located 
rather close to the surface. This is because of huge heat capacity of 
stellar interior.
Also, in the consistent approach, the energy conservation should should 
take into account the energy leaks to the differential rotation and 
magnetic activity,
as well as heating from dissipation of the flow and magnetic field.

In my model I  use the reference thermodynamic  structure of a star 
0.3Ms which was computed with help of MESA.
The 2D equation for the mean-field heat transport was solved for 
perturbation of the mean entropy  caused by effects of the global
rotation and magnetic field. Now I would like to check if the obtained 
large-scale flow and magnetic field will break the reference model.
The approach given in your paper would be ideal to my purpose. However, 
in the first step I would like to start from a more simpler one.
Thanks!
Valery

> If you are going to include the effects of a magnetic pressure, you will
> be have to be careful to ensure thermodynamic consistency.  One way to
> approach this for magnetic fields is discussed in Feiden & Chaboyer
> 2012, ApJ, 761, 30.
>
> cheers,
> Brian
>
>
> On 7/29/16 12:55 PM, Bill Paxton wrote:
>> Hi Craig,
>>
>> Good to hear you are also interested.  My goal, as I explained to Valery, is to provide the hooks in mesa/star so you crazy guys can try things -- it's the "E" in MESA at the level of things that require new software development.  You and Manos are already experienced with this idea.
>>
>> My hope is we can do the current task by adding a new pressure component so that the total pressure in mesa/star is P = Pgas + Prad + Pmag.
>> I'll modify the guts of mesa star to include Pmag, but the actual code to calculate it at each cell will be done by a "hook" routine so it can be developed independently of the mainline mesa code.  Does that sound like it would give you enough rope to take care of the rest of the hanging?  ;)
>>
>> Cheers,
>> Bill
>>
>>
>>
>>
>>
>>
>> On Jul 29, 2016, at 8:57 AM, Craig Wheeler wrote:
>>
>>> We had meant to add our prescription for the MRI dynamo
>>> to MESA. Perhaps there can be some joining of forces here.
>>>
>>> Craig Wheeler (for Manos, who did the work)
>>>
>>> On 7/28/16 9:31 PM, Valery Pipin wrote:
>>>> Dear  List,
>>>>
>>>> I wonder if MESA has a possibility to check effects of large-scale
>>>> magnetic field and flow on the stellar structure.
>>>>
>>>> I have computed a set of nonlinear dynamo models. They include the 3D
>>>> mean-field dynamo coupled with angular momentum balance and heat transport.
>>>>
>>>> The model use the reference thermodynamic  structure of a star 0.3Ms of
>>>> age 1Gyr  which was computed with help of MESA using the solar composition.
>>>>
>>>> The equation for the mean-field heat transport was solved for
>>>> perturbation of the mean entropy caused by effects of the global
>>>> rotation and magnetic field.
>>>>
>>>> In 1D stellar structure code the effect of mixing due to meridional
>>>> circulation can be treated as an addition to diffusion and effect of
>>>> magnetic field via the averaged addition to pressure.
>>>>
>>>> Both factors vary along the radius. Can I add them to the code and in
>>>> what place. I would appreciate if you have some example.
>>>>
>>>> The test suite contains example for 15M star with dynamo. I don't
>>>> understand where parameters of the magnetic field are defined?
>>>>
>>>> Thanks
>>>>
>>>> Valery
>>>>
>>>>
>>>>
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>>> -- 
>>> J. Craig Wheeler
>>> Samuel T. and Fern Yanagisawa Regents Professor of Astronomy
>>> President, American Astronomical Society, 2006-2008
>>> Department of Astronomy
>>> 2515 Speedway, Stop C1400
>>> Austin, TX 78712-1205
>>> 512-471-6407
>>> http://www.as.utexas.edu/~wheel
>>> http://ebooks.cambridge.org/ebook.jsf?bid=CBO9780511536625
>>> http://www.amazon.com/Krone-Ascending-ebook/dp/B00926QEGW
>>>
>>>
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