[Mesa-users] Energy conservation on the main sequence

[RICHARD H D TOWNSEND]

Sure thing -- attached! Note that this is using the 10398 release.






> On Feb 17, 2019, at 2:20 PM, Bill Paxton <paxton at kitp.ucsb.edu> wrote:
>
> Hi Rich,
>
> Please provide inlists etc so we can play along with you, starting by being able to reproduce your plots.
>
> Thanks,
> Bill
>
>> On Feb 17, 2019, at 12:14 PM, RICHARD H D TOWNSEND via Mesa-users <mesa-users at lists.mesastar.org> wrote:
>>
>> Hi folks --
>>
>> I'm writing to ask about energy conservation on the main sequence, for a solar-mass star. I'm not yet sure whether this is more of a question about stellar evolution, or about MESA.
>>
>> In the attached figure, I plot two quantities as a function of time:
>>
>> tot_E_change -- the total energy change across each timestep
>> total_energy_sources_and_sinks -- the total energy sources/sinks across each timestep
>>
>> For this evolutionary stage, total_energy_sources_and_sinks is practically identical to (L_nuc - L)*dt, where L_nuc is the nuclear luminosity, L the surface luminosity, and dt the timestep.
>>
>> My understanding is that the two quantities should align perfectly -- the net energy gain/loss is matched by a change in the star's total energy (which, according to the virial theorem, will result in an expansion/contraction). But that's clearly not what we see; while total_energy_sources_and_sinks is always positive (with the exception  of the ZAMS), the tot_E_change is initially negative and only becomes positive later on in the evolution.
>>
>> I'm clearly missing something important, but I'm not sure what. So, can anyone help clarify what's going on?
>>
>> cheers,
>>
>> Rich
>>
>> <energe-change.pdf>_______________________________________________
>> mesa-users at lists.mesastar.org
>> https://lists.mesastar.org/mailman/listinfo/mesa-users
>>
>

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