[mesa-users] extra heat source in mesa star

[Bill Paxton]

Hi Yevgeni,

As you know, there are a couple of simple schemes for adding energy, either uniformly by setting the 'extra_power_source' control or near surface to model irradiation by setting 'flux_for_hemisphere_irradiation'.    But your case goes beyond those.

The general scheme for adding extra heat involves writing a few lines of code.  Look at star/public/other_energy.f.   The routine 'do_other_energy' is called from inside star to set the vector 's% extra_heat'.  The value of s% extra_heat(k) is in ergs/g/sec; it will be added to the energy generation term for cell k along with nuclear reactions.  You'll want to change that to set extra_heat(k) according the your rule.  You can access information such as the radius for the outer edge of cell k as s% r(k).   Here is a little example that turns on extra heat depending on radius.

      subroutine do_other_energy(s, ierr)
         ! set s% extra_heat(k) to ergs/g/sec average for cell k
         use const_def, only: Rsun
         type (star_info), pointer :: s
         integer, intent(out) :: ierr
         integer :: k
         ierr = 0
         ! here is an example of calculating extra_heat for each cell.
         do k = 1, s% nz
            if (s% r(k) > 0.7*Rsun .and. s% r(k) < 0.9*Rsun) then
               s% extra_heat(k) = 1d3*exp(-10*(s% r(k) - 0.8*Rsun)**2) ! 10^3 erg/g/s at peak
            end if
         end do
         s% d_extra_heat_dlnd(:) = 0 ! obsolete and will go away in future release
         s% d_extra_heat_dlnT(:) = 0 ! obsolete and will go away in future release
      end subroutine do_other_energy


After you edit other_energy.f, change to the mesa/star/test directory and do 
./mk
./ck
./export

The ./ck should not produce any output (that means it is okay).
The ./export makes your changes available to your work directories.

In the not-too-distant future I'll be changing the way this works to make it a bit easier (by using the Fortran2003 feature of having pointers to procedures as elements of derived types).  But until then, you'll need to go through the sequence of edit, make & export from star/test, and then remake and run in your work directory.

Let me know how it goes!

Cheers,
Bill



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