[Mesa-users] Mesa-users Digest, Vol 67, Issue 4

[Evan Bauer]

Hi Jaime,

Unfortunately, those ionization outputs that you are using were mostly undocumented and have been removed from more recent versions of MESA. The only documentation for the code used to produce them is in $MESA_DIR/ionization/preprocessor/README:

########################################
#
#  Thomas-Fermi Debye-Huckel code
#  written by Francois Hebert, 2009-2010
#
#  this code calculates the charge state
#   of a ÔheavyÕ nucleus in a dense plasma
#   of lighter, fully-ionized, atoms.
#  ex: iron in a degenerate helium plasma
#
########################################

To learn more beyond that, you would have to read the code in that preprocessor directory.

The ionization module has been removed from more recent versions of MESA, but the EOS module also has some information about ionization that gets reported as the total number of free electrons per nucleon: free_e.

Cheers,
Evan


> On Feb 7, 2023, at 7:49 AM, Jaime Montes Norniella via Mesa-users <mesa-users at lists.mesastar.org> wrote:
> 
> Hi Evan.
> 
> I'm using mesa-r11701 and the model is in the folder “test_suite” with the name “1M_pre_ms_to_wd” but I examine only profiles from the ZAMS to the bottom of the RGB.
> Tha variables I need for obtain the ionization degrees of H and He (first and second in this case) are:
> fH= “neutral_fraction_H”, fHe = “neutral_fraction_He” and  zHe = “avg_charge_He"
> and the formulas for the ionization degrees are:
> iH = 1 - fH;
> iHe1 = 1 - fHe;
> iHe2 = zHe / iHe1 - 1.
> In the He formulas it is taken into account that He 1 time ionized appears in the two He ionization equations.
> In other similar models it also happens the ionization gap.
> 
> 
>> El 7 feb 2023, a las 13:00, mesa-users-request at lists.mesastar.org escribió:
>> 
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>> Today's Topics:
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>>  1. Re: Theoretical question about ionization (Evan Bauer)
>> 
>> 
>> ----------------------------------------------------------------------
>> 
>> Message: 1
>> Date: Mon, 6 Feb 2023 15:31:41 -0500
>> From: Evan Bauer <evan.bauer.astro at gmail.com>
>> To: Jaime Montes Norniella <jmn at usal.es>
>> Cc: mesa-users <mesa-users at lists.mesastar.org>
>> Subject: Re: [Mesa-users] Theoretical question about ionization
>> Message-ID: <46AADA2C-5716-4EA2-B7A4-29AB18F9D1F2 at gmail.com>
>> Content-Type: text/plain;	charset=us-ascii
>> 
>> Hi Jaime,
>> 
>> Could you provide some more detail about what kind of stellar model you're looking at, which MESA version you're using, and which specific output from MESA you're using to quantify ionization? There are a few possible answers to your question depending on those details.
>> 
>> Cheers,
>> Evan
>> 
>>> On Feb 4, 2023, at 11:58 AM, Jaime Montes Norniella via Mesa-users <mesa-users at lists.mesastar.org> wrote:
>>> 
>>> The MESA profiles frequently show an ionization gap in between the nucleus and the atmosphere, but much more near the nucleus.
>>> I think that this gap is because de lack of pressure ionization once the pressure decays away of the nucleus.
>>> Ionization returns to be complete farther away supposedly by the major effect of temperature which decays slowly.
>>> My question is: How MESA implements pressure ionization, knowing that no perfect theory is at hand (Kippenhahn, Stellar Structure, page 138)?
>>> 
>>> All your ideas are welcome.
>>> 
>>> Thanks.
>>> 
>>> Jaime Montes.
>>> University of Salamanca, Spain._______________________________________________
>>> mesa-users at lists.mesastar.org
>>> https://lists.mesastar.org/mailman/listinfo/mesa-users
>>> 
>> 
>> 
>> 
>> End of Mesa-users Digest, Vol 67, Issue 4
>> *****************************************
> 
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