[Mesa-users] A typo in atm module?

[Warrick Ball]

Hi Yixiao,

I think you're right that this is a typo but I think the typo is that 
`d_logg_dln?` should be `d_lng_dln?`, where I'm using `?` in place of `M` 
or `R`.  The only places that those two variables are used are in the 
derivatives

     dP0_dln? = d_logg_dln?*P0

a few lines later.  To detail the maths, we're doing something like

     dP0          dlnP0          d      tau * g         dlng
     ————  = P0 . ————— = P0 . ———— ln  ——————— =  P0 . ————
     dln?         dln?         dln?      kappa          dln?

which is exactly what's in the code, except that there's a misleading 
variable name.

Cheers,
Warrick





------------
Warrick Ball
Postdoc, School of Physics and Astronomy
University of Birmingham, Edgbaston, Birmingham B15 2TT
W.H.Ball at bham.ac.uk
+44 (0)121 414 4552


On Wed, 24 Oct 2018, mesa-users at lists.mesastar.org wrote:

> 
> Dear MESA developers and users,
> 
> 
> There might be a small problem in the grey atmosphere routine "eval_grey" in mod_atm.f90.
> 
> 
> The derivative used in "eval_grey", d_logg_dlnR should equals to -2/ln10 if assuming surface gravity g is propotional to GM/R^2. Similraly, d_logg_dlnM = 1/ln10. 
> 
> 
> This is indeed the case in other part of atmosphere module (e.g., routine "do_atm_get" in mod_atm.f90). However, in "eval_grey" they are set to be
> 
> d_logg_dlnR = -2 
> 
> d_logg_dlnM = 1
> 
> 
> Is this a typo or I misunderstood something?
> 
> 
> Thanks,
> 
> Yixiao Zhou
> 
> PhD student
> 
> RSAA
> 
> ANU
> 
> 
>