[mesa-users] MESA code Questions!!

[Bill Paxton]

take a look at star/test_suite/example_solar_model/inlist_solar_model.   it does this
      
      ! atomic diffusion
      do_element_diffusion = .true. ! determines whether or not we do diffusion
      diffusion_dt_limit = 7d11 ! no element diffusion if dt < this limit (in seconds)
      diffusion_T_full_on = 1d3
      diffusion_T_full_off = 1d3
      
      diffusion_calculates_ionization = .true.

      diffusion_num_classes = 4 ! number of classes of species for diffusion calculations
      diffusion_class_representative(1) = 'h1'
      diffusion_class_representative(2) = 'he4'
      diffusion_class_representative(3) = 'o16'
      diffusion_class_representative(4) = 'fe56'
   
      ! in ascending order.  species goes into 1st class with A_max >= species A
      diffusion_class_A_max(1) = 2
      diffusion_class_A_max(2) = 4
      diffusion_class_A_max(3) = 16
      diffusion_class_A_max(4) = 10000
         
      diffusion_use_isolve = .true.
      diffusion_rtol_for_isolve = 1d-4
      diffusion_atol_for_isolve = 1d-5
      diffusion_maxsteps_for_isolve = 1000
      diffusion_isolve_solver = 'ros2_solver'

b


On Jul 13, 2015, at 11:06 AM, Farag, Ebraheem Khaled wrote:

> how exactly do i turn it on?
> From: Josiah W. Schwab [jwschwab at berkeley.edu]
> Sent: Monday, July 13, 2015 12:06 PM
> To: Bill Paxton
> Cc: Farag, Ebraheem Khaled; mesa-users group
> Subject: Re: [mesa-users] MESA code Questions!!
> 
> No, Ebraheem has not turned on diffusion.  Perhaps my reply was too oblique of a hint to do so :)
> 
> Josiah
> 
> On Mon, Jul 13, 2015 at 10:59 AM, Bill Paxton <paxton at kitp.ucsb.edu> wrote:
> diffusion is not turned on by default, but I assume you have turned it on as in the sample solar model test case.
> even with diffusion on, the surface layers may be mixed into the convective region, so you'll only see changes in abundances that impact the entire convective region.  such things might happen -- but only if the burning effects are getting into the convective region somehow.  i'm not an expert of that question, but I believe there are some folks on mesa-users who have considered this (Matteo?).
> 
> b
> 
> 
> 
> 
> On Jul 13, 2015, at 10:46 AM, Farag, Ebraheem Khaled wrote:
> 
> > The other models, I've seen from lanl pulsation codes are using Burgers' diffusion treatment as implemented by cox et al.(1989) and nuclear reaction rates from Angulo et al.(1999) with correction to the N14 rate from FOrmicola et al.(2004)
> >
> > -I'm trying to mirror these abundance models through MESA by using unreleased Opacity tables
> >
> > does this provide any info?
> > ________________________________________
> > From: Josiah Schwab [jwschwab at berkeley.edu]
> > Sent: Monday, July 13, 2015 11:30 AM
> > To: Farag, Ebraheem Khaled
> > Cc: Francis Timmes; mesa-users
> > Subject: Re: [mesa-users] MESA code Questions!!
> >
> > Hi Ebraheem,
> >
> >> I'm only having one small strange problem.
> >>
> >> my surface abundances are exactly the same over the whole lifespan of
> >> the sun. is there something wrong with my model?
> >>
> >> This is very saddening to see. A fix would be greatly appreciated!
> >
> > What physics do you think will cause them to change?
> >
> > Josiah
> >
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