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

[Sergei Nayakshin]

Hi Ana-Maria,

I'm new to MESA myself, but I also come in from the planet formation side, and I imagine that the problems you have are physical rather than numerical. If I understand it correctly you're trying to simulate the pre-collapse stage of planet formation, i.e., a planet so fluffy and cool that it is dominated by molecular H. The gas density at the Bondi radius would be of the order of the accretion disc density, which is probably 10^-10 g/cm^3, and temperature T ~ 100 K, although these numbers could vary with the separation of the planet from the star.

Perhaps MESA creators could comment on this further as I am out of my depth on how MESA would deal with this parameter space.

Cheers,
Sergei.



On 25 Apr 2014, at 18:03, Josiah Schwab wrote:

> Hi Ana-Maria,
> 
> I've taken this discussion back onto mesa-users, as we're starting to
> get out of my area of expertise.  Some of the people who have done
> planets in MESA (e.g., Phil Arras) may be able to be more helpful.
> 
>> I modified the other_atm subroutine and made sure it's active. I tried
>> testing this by modifying the 'inlist_create_1.0_MJ_10.0_ME_2.0_RJ' in
>> the 'make_planets' test suite, with M = 6 Earth masses and R = its
>> Bondi radius G * Mp / cs^2. The code compiles and runs, but has
>> trouble creating an initial model -- once it has reached its maximum
>> number of iterations, however, it does seem to produce a solution (and
>> it writes it in the profile.data files etc.), but the mass and initial
>> radius it outputs are very different from my initial
>> specification. I've tried adjusting initial_model_relax_num_steps, the
>> timestep control, the maximum age / model number etc., but haven't
>> been successful so far. I'm wondering if it's just a question of
>> better adjusting some of these parameters, or if in general MESA has
>> difficulties in creating such low mass / large radius models...
> 
> If you haven't, you'll want to take a look at Section 2 in Paxton et
> al. (2013), where the routines that create the initial conditions in the
> make_planets test case are discussed.  They quote a lower mass limit of
> 0.1 M_{Jupiter} for that approach.
> 
> The initial conditions you propose don't make sense to me (e.g., are you
> in hydrostatic equilibrium out to the Bondi radius?  do you get 6
> M_{Earth} of balls of gas like that, but no core?), but given my limited
> knowledge of planet formation, I'll let the experts chime in.
> 
> Best,
> Josiah
> 
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