[Mesa-users] Ideal gas law

[Jason Wright]

Thank you!  That's just what I was looking for.

On Tue, Feb 16, 2021 at 3:17 PM mutlu yildiz <mutluyildiz1 at gmail.com> wrote:

> Dear Jason,
>
> It is due to the Coulomb pressure. Another view of this effect can be seen
> in figure 1 of Yıldız & Kızıloğlu (1997) for the present Sun:
>
> https://ui.adsabs.harvard.edu/abs/1997A%26A...326..187Y/abstract
> or
> https://arxiv.org/abs/astro-ph/9706228
>
> Best Regards,
> Mutlu Yıldız
>
> On Tue, Feb 16, 2021 at 9:29 PM Jason Wright via Mesa-users <
> mesa-users at lists.mesastar.org> wrote:
>
>> I'm using MESA in a graduate course and I've managed to stump myself with
>> a problem I assigned.
>>
>> I am looking at the profile of an ordinary 1 solar mass ZAMS star. I
>> assigned the students the task of testing the perfect gas law.  We find a
>> large, smooth violation of the law in the convective zone, with anomalies
>> up to 7%.  I attach the anomalies here (I hope this image comes through the
>> mailing list, if not you should be able to see the image at
>> https://sites.psu.edu/astrowright/files/2021/02/hw3.9.1b.pdf).
>>
>> [image: Screen Shot 2021-02-16 at 1.14.25 PM.png]
>> Note that I'm plotting the x axis using the logit function to
>> logarithmically stretch out both the core and envelope (core on the left,
>> envelope on the right). m = M/2 is at abscissa value 0.
>>
>> I can't fathom why the perfect gas law does not hold in the envelope.
>> The negative anomaly in the core I understand (electron degeneracy
>> pressure) but the rest has me baffled. It roughly lines up with the
>> ionization of He, but not perfectly and anyway, why would that matter?
>>
>> I am plotting using the variables logrho, pgas, mu, and logT.  I've tried
>> using cell boundaries vs. centers, but that's not it (these things should
>> all be defined in the cell anyway).  I've tried using logP (total pressure
>> and get almost the same answer.  mlt_turb = 0 everywhere.  Radiation
>> pressure is not important anywhere.
>>
>> Thanks for any ideas!
>>
>> --
>>                                                 -
>> ---------------
>> Jason T Wright
>> Professor of Astronomy & Astrophysics
>> Director, Penn State Extraterrestrial Intelligence Center
>> Acting Director, Center for Exoplanets and Habitable Worlds
>> NEID Instrument Team Project Scientist <http://neid.psu.edu/>
>> he/him/his
>> *https://sites.psu.edu/astrowright/ <https://sites.psu.edu/astrowright/>*
>> @Astro_Wright
>>
>> <http://twitter.com/Astro_Wright>
>> _______________________________________________
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>>
>>
>
> --
> Ege Üniversitesi Fen Fakültesi
> Astronomi UBB 35100 Bornova İzmir
>


-- 
                                                -
---------------
Jason T Wright
Professor of Astronomy & Astrophysics
Director, Penn State Extraterrestrial Intelligence Center
Acting Director, Center for Exoplanets and Habitable Worlds
NEID Instrument Team Project Scientist <http://neid.psu.edu/>
he/him/his
*https://sites.psu.edu/astrowright/ <https://sites.psu.edu/astrowright/>*
@Astro_Wright

<http://twitter.com/Astro_Wright>
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