[Mesa-users] Creating a Highly Irradiated Super-Earth

[Brian Jackson]

Thanks for the response, Dr. Lauer. Unfortunately, it didn't seem to
help (unless I should try something even smaller than 1e-12...?):

                                                     dt
3.4726514269628949D-15
                                     min_timestep_limit
9.9999999999999998D-13

 stopping because of problems dt < min_timestep_limit


terminated evolution: cannot find acceptable model

termination code: min_timestep_limit
pause_before_terminate: hit RETURN to continue

---

I see that others have said they would follow up. Thanks for that.

Brian

On Fri, Jan 24, 2020 at 1:57 PM amber lauer <amber.lauer at tunl.duke.edu> wrote:
>
> 1D-7 seems high for a minimum timestep. Where do you see that is "recommended"? When working with a new model where you have difficulties with stability, it often helps to loosen the computational constraints until you get a stable version. Minimum timestep is one of the first ones I change.
> =================================
> Dr. Amber Lauer
> Postdoctoral Researcher
> Triangle Universities Nuclear Lab
> Duke University
> amber.lauer at tunl.duke.edu
>
>
> On Fri, Jan 24, 2020 at 2:53 PM Brian Jackson <bjackson at boisestate.edu> wrote:
>>
>> I've conducted additional experiments, and I think I'm starting to see
>> what the issues might be.
>>
>> I've attached inlists and a model for a slightly different approach.
>> The model calculation behaves fine until about 4 Gyrs out, when the
>> timestep suddenly plunges and the code fails to complete the run. For
>> some reason, the central degeneracy parameter goes haywire shortly
>> before the run ends -- see attached History_Plot.png.
>>
>> Looking at the 2011 MESA instrument
>> (https://urldefense.proofpoint.com/v2/url?u=https-3A__ui.adsabs.harvard.edu_abs_2011ApJS..192....3P_abstract&d=DwIBaQ&c=imBPVzF25OnBgGmVOlcsiEgHoG1i6YHLR0Sj_gZ4adc&r=IZ3U2LUL6yhDK-Uf8F_eU9W85o61MM43boq-nVwHt38&m=VUMjn3TtPcQDhrIdYRUN4iHF2HTgi2wOtFYjHuaOou4&s=wpqHgLeePFLJvg_YLSXwPgXc1RkPvMS8vkgozvkrNbU&e= ), it
>> seems the model core may be nearing a transition in the equation of
>> state (log(density) = -0.19, log(temp) = 3.79 -- see attached Figure
>> 1). Is there a reason why that transition would severely and abruptly
>> modify the degeneracy parameter? Is there a way to smooth this
>> evolutionary phase?
>>
>> Or have I completely misunderstood what's going on?
>>
>> Thanks,
>> Brian
>>
>> On Wed, Jan 22, 2020 at 5:58 PM Brian Jackson <bjackson at boisestate.edu> wrote:
>> >
>> > Dear MESA Users,
>> > I am still struggling to create highly-irradiated super-Earths using MESA.
>> >
>> > I have attached the inlists and saved models I'm using to create a
>> > 20-Earth mass planet with an envelope mass fraction of 20% (i.e., a
>> > core mass of 16 Earth masses) and an irradiation 20 times Earth's
>> > (i.e., 2.72e7 ergs/s/cm^2).
>> >
>> > I attempt to create the planet by irradiating a gas giant planet and
>> > then relaxing the mass down to my desired mass. (I've found doing it
>> > the other way around leads to badness.) I've tried tweaking lots of
>> > settings, but nothing seems to work. In the end, I wind up with a
>> > timestep below the suggested minimum of 9.9999999999999995D-07.
>> >
>> > I am using Mac OS 10.13.1, MESA 11701, and the most recent version of
>> > the SDK (August 30 2019).
>> >
>> > Please forgive me if I forgot any required information.
>> >
>> > Thanks,
>> > Brian
>> _______________________________________________
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>>