[Mesa-users] Doubt on overshoot parameters

[Pedro Nuno David Gomes]

Dear MESA users,

I have a doubt on the overshoot parameters I was hoping you could help 
me clarify. I'm sure this is a very simple doubt, but I can't wrap my 
head around it.

I have an inlist of a previous MESA release (release 7456) with the 
following controls regarding the overshooting,

      overshoot_f_below_nonburn = 0.018
      overshoot_f_above_burn_h = 0.018
      overshoot_f_above_burn_he = 0.018

 From what I understood, using these controls one establishes that 
overshoot occurs at a distance 0.018*H from the boundaries of convective 
regions, with H being the scale height. Right?

Now, I was trying to run the same controls in the latest MESA release 
but I got an error: "Fortran runtime error: Cannot match namelist object 
name overshoot_f_below_nonburn".

So, the previous controls changed with posterior releases. I'm having 
some doubts understanding how to implement these controls in the current 
release. At first I simply thought about replacing them directly with 
(what I think are) the updated controls,

      overshoot_f_above_burn_h_core = 0.018
      overshoot_f_above_burn_h_shell = 0.018
      overshoot_f_below_nonburn_shell = 0.018

(I'm not considering helium burning regions because I'm only interested 
in analysing the lower Red Giant Branch). But when I run MESA I get an 
error: "ERROR: when using overshooting above, must set f0_above > 0".

 From what I read on the controls defaults, namely

      "The switch from convective mixing to overshooting happens at a 
distance f0*Hp into the convection zone
      (...) where Hp is the pressure scale height at that location.",

I also have to define f0. So, given this explanation, what I thought I 
had to do was replace f with f0,

      overshoot_f0_above_burn_h_core = 0.018
      overshoot_f0_above_burn_h_shell = 0.018
      overshoot_f0_below_nonburn_shell = 0.018

And in this case MESA runs. However, I'm not sure if this is the way - 
from what I read after, namely

       "for example, if you want overshooting of 0.2 scale heights beyond 
the normal edge, you might want
        to back up 0.05 scale heights to get the diffusion coeff from 
near the edge and then go out by 0.25
        scale heights from there to reach 0.2 Hp beyond the old boundary. 
In the inlist this would mean setting
        the “f0” to 0.05 and the “f” to 0.25."

I have to define in the inlist controls with f and f0 simultaneoulsy; 
so, from my understanding, this would mean writting, for instance,

      overshoot_f_above_burn_h_core = 0.018
      overshoot_f_above_burn_h_shell = 0.018
      overshoot_f_below_nonburn_shell = 0.018

      overshoot_f0_above_burn_h_core = 0.001
      overshoot_f0_above_burn_h_shell = 0.001
      overshoot_f0_below_nonburn_shell = 0.001

Is any of these the right way, or am I missing something? If this is the 
case, could you help me understand how to replace the previous controls 
with these values?

Thank you for your attention. Regards,

Pedro