[Mesa-users] Energy conservation on the main sequence

[Bill Paxton]

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
> 
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