[mesa-users] MESA for giant planet initial thermal evolution

[Bill Paxton]

you'll handle changing the mass accretion rate using run_star_extras too.   you just set the "mass_change" parameter from your code instead of in the inlist.  

to get started with run_star_extras, read the "modifying the code" page on the mesa website.
http://mesa.sourceforge.net/run_star_extras.html

that page also tells you how to use "hooks" --- you'll be using the "other_atm" hook to set surface boundary conditions.

I'm going to let some other folks on the mesa-users list jump in at this point to guide you with the details.

Cheers,
Bill









On Apr 23, 2014, at 11:50 AM, Ana-Maria Piso wrote:

> 
> 
> 
> On Wed, Apr 23, 2014 at 1:28 PM, Bill Paxton <paxton at kitp.ucsb.edu> wrote:
> 
> On Apr 23, 2014, at 7:02 AM, Ana-Maria Piso wrote:
> 
>> Hi,
>> 
>> I am new to MESA, so I apologize if this question has already been answered somewhere else. I would like to use MESA to model the evolution of a giant planet embedded in a gas disk -- the standard core accretion calculation, assuming that the core has a fixed mass. The 'make_planets' test case is probably a good place to start, but I need to:
>> 
>> (a) fix the outer boundary conditions to constant T and P, which I haven't seen as an option in the standard MESA controls
> 
> mesa has lots of fancy outer boundary conditions, but it is missing the simple case of fixed T and P --- I can show you how to do it yourself if you're willing to plunge into using run_star_extras and writing a small routine to replace the standard atm package.   let me know if you'd like to try that.
> 


> Sure, I would like to try that since it seems like the cleanest option. I've used python a lot, but not C, so if you could show me how to write this subroutine in run_star_extras, that'd be great.



> 
>  
> 
> alternatively, have you considered using this:
> 	which_atm_option = 'grey_irradiated'
>             ! based on Guillot, T, and Havel, M., A&A 527, A20 (2011).
> 
> see the "irradiated_planet" test case in star/test_suite.
> 
> 
>> (b) include a variable mass accretion rate M_dot = (M_i+1 - M_i) / dt, where i is the current model.
> 
> the simplest way to start is to set a constant rate in your inlist --- seach for "mass gain or loss" in star/defaults/controls.defaults
> 
> That sounds like a good start! However, since the mass accretion rate is not going to stay constant throughout the evolution, is there a simple way to vary Mdot while evolving the planet based on previous steps?
> 
> Thanks,
> Ana
>  
> 
>       mass_change = 0d0 ! rate of accretion (Msun/year).  negative for mass loss.
>          ! this only applies when the wind scheme = ''
> 
> 
> -Bill
> 
> 
> 
> 
>> 
>> I'm not sure how to do this / where to start, so any help would be greatly appreciated.
>> 
>> Best,
>> Ana  
>> 
>> -- 
>> Ana-Maria Piso
>> Graduate Student 
>> Harvard University Department of Astronomy
>> apiso at cfa.harvard.edu
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> 
> 
> -- 
> Ana-Maria Piso
> Graduate Student 
> Harvard University Department of Astronomy
> apiso at cfa.harvard.edu

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