[Mesa-users] Irradiating a Planet

Bill Paxton paxton at kitp.ucsb.edu
Mon Dec 2 19:22:06 EST 2019


Hi Brian,

You might check in detail what is happening near the surface of the model.  You have

	column_depth_for_irradiation = 300.0 ! 3.d2 cm^2/g

but what does that mean in terms of number of zones?   is that spread over 20 zones or 2?  if the irradiation is concentrated in a small number of zones, that might cause problems.

you could use pgstar to check this by changing the x axis to zone and setting the axis bounds to focus on the 50 or so zones at the surface.   that might provide some insight.    more useful than seeing a vertical line at q=1.  ;)

-b


> On Dec 2, 2019, at 4:07 PM, Brian Jackson <bjackson at boisestate.edu> wrote:
> 
> Evan,
> Thanks for responding.
> 
> What I am seeing does not seem to be the same as Figure 56 -- see attached
> screenshot. Figure 56 shows that both energies are negative when the
> mass coordinate q is equal to the total mass (i.e., at the top of the
> atmosphere). In my model, however, the specific energy is negative
> throughout much of the model, but then near the surface (near q = 1),
> the energy becomes positive. When that happens in the time evolution,
> the model slows way down and takes smaller and smaller time steps. I
> also notice that the model planet's radius begins to increase without
> any obvious limit, eventually exceeding the size of the Sun (which
> seems strange for a 29 Earth mass planet with about a 10% gaseous
> atmosphere).
> 
> So am I wrong in thinking the planet has become unbound?
> 
> In case it's helpful, I've attached the final inlist, pgstar inlist,
> and loaded model. Apologies if I missed anything.
> 
> Thanks again,
> Brian
> 
> 
> On Mon, Dec 2, 2019 at 11:09 AM Evan Bauer <ebauer at physics.ucsb.edu> wrote:
>> 
>> Hi Brian,
>> 
>> My guess is what you’re seeing is that the ionization and molecular dissociation energies are included in the definition of energy from the EOS. See section 8.4 and figure 56 of MESA 4. Does that seem consistent with what you see in your model?
>> 
>> Cheers,
>> Evan
>> 
>> 
>>> On Nov 29, 2019, at 3:41 PM, Brian Jackson <bjackson at boisestate.edu> wrote:
>>> 
>>> All,
>>> Happy Post-Thanksgiving.
>>> 
>>> If I can trouble you all once more, I've made some modifications to my
>>> calculations based on your input. However, when I track the
>>> total_energy parameter during the evolution, I find that, as I
>>> irradiate my planet, near the top of the atmosphere, the total_energy
>>> becomes positive. If I'm interpreting correctly, that means the
>>> planet's atmosphere is becoming unbound.
>>> 
>>> Could someone please confirm this interpretation or correct it?
>>> 
>>> Thanks,
>>> Brian
>>> 
>>> On Wed, Nov 20, 2019 at 7:38 PM Josiah Schwab via Mesa-users
>>> <mesa-users at lists.mesastar.org> wrote:
>>>> 
>>>> Hi Brian,
>>>> 
>>>>> After creating that model (attached as
>>>>> planet_setEntropy_29ME_9percent_10kB.mod), I then attempted to evolve
>>>>> that model for several Gyrs under irradiation (as indicated in the
>>>>> attached inlist). However, the calculation stalls out as the time-step
>>>>> gets smaller and smaller.
>>>> 
>>>> Thanks for including the inlists/model.
>>>> 
>>>>> Could you suggest any way to keep that calculation from stalling? I am
>>>>> using Mac OS 10.13.1, MESA 11701, and the most recent version of the
>>>>> SDK (August 30 2019).
>>>> 
>>>> In the terminal output, the dt_limit is "varcontrol".  That means that
>>>> the timestep is limited by zone-to-zone changes in temperature, density,
>>>> etc.  In the T-Rho diagram, things look pretty static. But if you add
>>>> 
>>>>   Profile_Panels1_win_flag = .true.
>>>>   Profile_Panels1_xmin = 8.78e-5
>>>> 
>>>> to your pgstar inlist, you'll be able to see heat from the irradiated
>>>> outer material moving deeper (in a Lagrangian sense) into the star.
>>>> 
>>>> You have to limit the x-axis to easily see this because this thermal
>>>> wave is quite thin in mass.  Following that requires short timesteps.
>>>> 
>>>> I just wanted to push back a bit on the statement that the calculation
>>>> is stalled.  Something is happening in the model and MESA is
>>>> timestepping at the timescale to follow that.  I recognize that this is
>>>> not the Gyr timescale that you're interested in.
>>>> 
>>>> 
>>>> I don't know what your science case needs, but I would probably try
>>>> starting from a higher entropy model.
>>>> 
>>>> Josiah
>>>> _______________________________________________
>>>> mesa-users at lists.mesastar.org
>>>> https://lists.mesastar.org/mailman/listinfo/mesa-users
>>>> 
>>> _______________________________________________
>>> mesa-users at lists.mesastar.org
>>> https://lists.mesastar.org/mailman/listinfo/mesa-users
>>> 
>> 
> <Screen Shot 2019-12-02 at 5.04.51 PM.png><inlist_pgstar><planet_irradiated_29ME_9percent_10kB_logflux_9.524.mod><inlist>_______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users
> 



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