[Mesa-users] avg_charge in MESA

[Farag, Ebraheem]

I think you're looking at the old webpage for 15140, i'd look at the 24.08.1 version :

https://docs.mesastar.org/en/r24.08.1/using_mesa/extending_mesa<https://docs.mesastar.org/en/r15140/using_mesa/extending_mesa.html>.

Those errors you noted have been caught and are corrected in the latest (development) version as well:
https://docs.mesastar.org/en/latest/, so maybe follow this instead.

If you add the profile columns correctly, it should show up your profiles#.data files?

-EbF
________________________________
From: Jason Wright <astrowright at gmail.com>
Sent: Thursday, February 27, 2025 11:52 AM
To: Farag, Ebraheem <ebraheem.farag at yale.edu>
Cc: mesa-users <mesa-users at lists.mesastar.org>
Subject: Re: [Mesa-users] avg_charge in MESA

thanks!  Working on this.

This section on how to add columns to run_star_extras.f90 seems buggy:

https://docs.mesastar.org/en/r15140/using_mesa/extending_mesa.html

      subroutine data_for_extra_profile_columns(id, n, nz, names, vals, ierr)
         integer, intent(in) :: id, n, nz
         character (len=maxlen_profile_column_name) :: names(n)
         real(dp) :: vals(nz,n)
         integer, intent(out) :: ierr
         type (star_info), pointer :: s
         integer :: k
         ierr = 0
         call star_ptr(id, s, ierr)
         if (ierr /= 0) return

         ! note: do NOT add the extra names to profile_columns.list
         ! the profile_columns.list is only for the built-in profile column options.
         ! it must not include the new column names you are adding here.

         ! here is an example for adding a profile column
         !if (n /= 1) stop 'data_for_extra_profile_columns'
         !names(1) = 'beta'
         !do k = 1, nz
         !   vals(k,1) = s% Pgas(k)/s% P(k)
         !end do


I think the pressure (P(k)) has been renamed Peos(k), is that right?

Still, even after successfully making run_star_extras with that change, I don't see beta showing up in the LOG files.  I'll keep poking around, though—probably a simple bug, although I'm not getting any error messages.

Jason

On Thu, Feb 27, 2025 at 10:47 AM Farag, Ebraheem <ebraheem.farag at yale.edu<mailto:ebraheem.farag at yale.edu>> wrote:
Hello Jason,

Unfortunately, the EOS in MESA does not calculate ionization directly. In previous MESA versions, the ionization module existed which could  estimate the ionization fraction. Recently, the ionization module was resurrected and re-included in mesa-releases, but consider it still a developmental feature (fine for classrooms, but not ready for science).

I can't provide much more details except that in the past, something like the "avg_charge_H" was calculated through a call to the ionization module:

               avg_charge_H = get_ion_info(ion_iZ_H,k,chem_isos% Z(ih1))

Where "get_ion_info", is a wrapper for the ionization library:

---
         real(dp) function get_ion_info(id,k,Z)
            use ionization_lib, only: eval_ionization
            integer, intent(in) :: id, k, Z
            integer :: ierr
            ierr = 0
            if (ionization_k /= k) then
               call eval_ionization( &
                  s% Z(k), s% X(k), s% Rho(k), s% lnd(k)/ln10, &
                  s% T(k), s% lnT(k)/ln10, ionization_res, ierr)
               ionization_k = k
            end if
            if (ierr /= 0) then
               get_ion_info = Z
            else
               get_ion_info = ionization_res(id)
            end if
         end function get_ion_info
---

Feel free to try using this wrapper and calling the ionization module for the values you're interested in (for example, by adding this into your run_star_extras as an extra profile column).

I hope this is helpful.

-EbF


________________________________
From: Mesa-users <mesa-users-bounces at lists.mesastar.org<mailto:mesa-users-bounces at lists.mesastar.org>> on behalf of Jason Wright via Mesa-users <mesa-users at lists.mesastar.org<mailto:mesa-users at lists.mesastar.org>>
Sent: Thursday, February 27, 2025 10:11 AM
To: mesa-users <mesa-users at lists.mesastar.org<mailto:mesa-users at lists.mesastar.org>>
Subject: [Mesa-users] avg_charge in MESA

Hi, all!  I'm once again using MESA to teach stellar structure and I've run into some curiosities and problems from my assignments four years ago.

The first is that a few output parameters I was relying on seem to have disappeared.  I was using the profile outputs

avg_charge [isotope]

but this no longer seems to be an allowed output.  The reason I want this number is to calculate the Coulomb pressure as part of an assignment to explore the EOS used by MESA.

Is there a way I can access these values? I tried the advertised profile outputs:

typical_charge [isotope]

but they are all zero.

Thanks,

--
                                                -
---------------
Jason T Wright
Professor of Astronomy and Astrophysics
Director, Penn State Extraterrestrial Intelligence Center
he/him/his
https://sites.psu.edu/astrowright/
https://bsky.app/profile/astrowright.bsky.social


--
                                                -
---------------
Jason T Wright
Professor of Astronomy and Astrophysics
Director, Penn State Extraterrestrial Intelligence Center
he/him/his
https://sites.psu.edu/astrowright/
https://bsky.app/profile/astrowright.bsky.social
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