[mesa-users] Vink_wind_eta

[Bill Paxton]

On May 23, 2015, at 4:25 AM, Zsolt Keszthelyi wrote:

> It's a little bit unlucky nomenclature though, since in stellar wind physics the eta is the so-called wind efficiency / performance number and has nothing to do with a numerical scaling factor. (It might be useful to change it in the next version.)


Hi,

In star/defaults/controls.defaults we describe the various etas like this for Reimers and Blocker winds:

         !### Reimers_wind_eta
         ! Parameter for mass loss by Reimers wind prescription.
         ! Reimers mdot is `eta*4d-13*L*R/M` (Msun/year), with L, R, and M in solar units.

         !### Blocker_wind_eta = 0
         ! Parameter for mass loss by Blocker's wind prescription.
         ! Blocker mdot is `eta*4.83d-9*M**-2.1*L**2.7*4d-13*L*R/M` (Msun/year),

Having stated that idea twice, we just hope the reader will make the leap to understand that they work similarly for the remaining kinds of winds.

So we use "parameter for mass loss" where you would use "wind efficiency / performance number".

In practice of course it is a numerical scaling factor for the strength of the wind.  At least it looks like that to me.  And it does that in the code.

If I'm missing something important about the role of eta in stellar wind physics, please educate me.  

Thanks,
Bill

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