[Mesa-users] compounding offset error with MESA and .gyre output

[David Arnett]

In order for linear analysis to be valid (gyre), the time step for a full
hydro model must be small enough. I would look for time scales for
nonstatic processes which might muddle the linear analysis.
are there any which are the same order as your time between models? Just a
suggestion; sometimes dynamics rears its (lovely) complex head ;-)

On Wed, Feb 27, 2019 at 11:18 PM Meridith Joyce via Mesa-users <
mesa-users at lists.mesastar.org> wrote:

> Hi All,
> Bit of an oddly specific question here:
>
> I'm stopping and starting MESA on very short time intervals (on the order
> of half a year, in some cases) and generating GYRE profiles at each of
> those times.
>
> Proceeding chronologically, for the first 5 or so such .gyre models out of
> a set of, say, 20, the stellar radius at the appropriate value of t in
> MESA's history file, say R(t), is in near exact agreement with the radius
> passed to the .gyre file.
> With increasing evolutionary time, however, an offset between R(t) in the
> history file and the radius given to .gyre (say R_gyre) emerges. The
> discrepancy between R(t) and R_gyre worsens the more .gyre models I try to
> produce from a single run of ./star.
>
> All of the .gyre files in a set are generated from a single evolutionary
> run---though that run may proceed discontinuously---using the same inlist
> and controls. I've attached one of my inlists for example.
>
> My instinct is that this is due to some quirk or error which iteratively
> compounds a loss of precision or numerical misalignment each time I stop
> and restart the models. The attached figures perhaps demonstrate my problem
> more clearly.
>
> Has anyone encountered this before or know a way around it?
>
> Thank you,
>
>
> Dr. Meridith Joyce
> PhD, Dartmouth College & SAAO
> RSAA Postdoctoral Fellow
> Australian National University
>
> _______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users
>
>

-- 
David Arnett
Regents Professor
Steward Observatory
University of Arizona

Facts are stubborn, but statistics are more pliable.  Mark Twain
Facts do not cease to exist because they are ignored.  Aldous Huxley
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