[Mesa-users] convergence problem

[sheyda najafi]

Dear Josiah

Thank you very much for your helpful suggestion. I have added the
following lines for the right hand side of the HSE equation  to the
subroutine "data_for_extra_profile_columns" as


        names(6) = 'right_hand_dlnpdm'
	do k = 1, s% nz
	vals(k,6) =(  (-(standard_cgrav * s% m(k))/(4.d0 * pi *(s%
r(k)**4.d0)))  +  (s% extra_dPdm(k))    )/(s% P_face(k))
         end do

and plotted the term as a function of radius.
Also the density and pressure as a function of radius in three
different epochs in the RGB phase are plotted in the attachement
(mail.mesa.pdf). I would be grateful if you could take a look at
plots.

what i can understand from the plots is that for "beta=1/sqrt(6)"
there are some density bumps which can not cause pressure gradient
since the extra term is negligible compared to the Newtonian one.
 But in the case "beta=800" since in the low density envelope of the
star, the extra term in HSE equation overcomes the gravitational term,
the density bump can cause pressure gradient via the extra term in HSE
equation. which makes rapid changes in the right hand side of HSE and
even makes it positive which means that (dP/dm > 0) in some radius and
cause the violation of the stability condition . in fact the HSE has
rapid changes in magnitude exactly at the place of density bump which
in my opinion can cause instability.

I look forward to your comments.

Thank you in advance



Sheyda

On 6/18/18, Josiah Schwab <jwschwab at ucsc.edu> wrote:
> Hi Shedya,
>
> Were you ever able to get oscillations that didn't depend on the space and
> time resolution of the model?  That was the most concerning part from my
> perspective.
>
> Even if you can't quite get there, as a point of presentation, it would
> probably be useful to show a little more about what's happening in the
> structure of the star.  The wiggles in the HR diagram are somewhat less
> informative than plots showing the magnitude of the the various forces in
> the outer layers of the star (gravity, pressure gradient, your extra force,
> etc.) and how they're changing as the star goes up the RGB.  That might
> help clearly explain to your reader why the models run into trouble at some
> point.
>
> Josiah
>
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