Begin The Great Documention

[Debraheem]

Addressing #766, and serving as a stepping stone for further documentation. I welcome all who would like join this effort by pushing documentation changes/updates into this pr.

[Mathijs-Vanrespaille]

The following fields in the profile columns list have caused me some pain in the past when searching for relevant profiles to study the temperature gradients in a star. In r24.03.1, all these fields are undocumented.

• gradL_sub_gradr
• gradP_div_rho
• gradT_excess_effect
• gradT_rel_err
• gradT_sub_a
• grada_face
• grada_sub_gradr
• diff_grads
• log_diff_grads
• mlt_D
• mlt_Gamma
• mlt_Y_face
• mlt_Zeta
• mlt_gradT
• mlt_log_abs_Y
• mlt_vc
• log_mlt_vc
• dvc_dt_TDC_div_g

PS: Awesome to see this push to improve the MESA documentation. Many thanks for setting this up!

[warrickball]

Why not just

Suggested change

	! in kerg per baryon, where kerg = (erg K^-1)
	! in erg per kelvin per baryon

or

Suggested change

	! in kerg per baryon, where kerg = (erg K^-1)
	! in (erg K^-1) per baryon

[pmocz]

I agree with you @warrickball ! It's just that kerg gets used all over in Mesa documentation and output headers, so I think we should correct these all at once. Should we do it in this PR?

[warrickball]

Ah, if it's a reasonably common unit, perhaps we don't need to change it, but I'd never encountered it before.

If we are going to change it in a lot of places at once, I agree with doing it in a separate PR.

[fxt44]

comment from the peanut gallery. i disagree with adding per baryon. electrons, leptons, have an entropy that is added to the total. photons, bosons, also have an entropy that is added in. an entropy of mixing is also added. none of these other contributions to the total entropy have baryons associated with them.

[warrickball]

As above:

Suggested change

	! in kerg per baryon, where kerg = (erg K^-1)
	! in erg per kelvin per baryon

or

Suggested change

	! in kerg per baryon, where kerg = (erg K^-1)
	! in (erg K^-1) per baryon

[warrickball]

For parity with other similar controls

Suggested change

	! criteria for stopping when Pgas/P <= Pgas_div_P_limit
	! stop when Pgas/P <= Pgas_div_P_limit

[warrickball]

Though we aren't being very consistent about monospace yet, I think this should be

Suggested change

	! composition controls in &controls.defaults.
	! composition controls in ``star/defaults/controls.defaults``.

[Mathijs-Vanrespaille]

The control max_allowed_nz currently has the following documentation:
Maximum number of grid points allowed. Array allowed to grow arbitrarily large if max_allowed_nz <= 0
Please clarify in the documentation what happens if the number of zones goes above this limit. Should the code reduce the number of zones to below the maximum again (if so, how does it do so?) or does the run end? In my experience, an error is thrown and the run ends.