[mesa-users] Vink_wind_eta

Tue May 26 16:09:25 EDT 2015

Hi, 

I was about to suggest the same thing! A further support is that this is basically already implemented in the 'Dutch wind'. 

Maybe 10 - 12 kK would be a good limit to distinguish between 'hot' and 'cool'. 

Cheers, 
 Zsolt 

> Von: Mathieu <mathren90 at gmail.com>
> An: mesa-users at lists.sourceforge.net
> Kopie: 
> Datum: Tue May 26 22:03:06 CEST 2015
> 
> Hi everyone,
> 
> since the wind mass loss is not directly connected with the burning 
> stage in the core, I would suggest avoiding to name the different wind 
> options according to the nuclear processes in the core.
> It seems a bit confusing to me.
> 
> Most of the mass loss algorithms apply in a given temperature range, so 
> I would suggest using something like:
> 
>   - wind_hot
>   - wind_cool
>   - wind_WR
> 
> and use a condition on the effective temperature (and surface hydrogen 
> abundance for the WR wind scheme) to switch between different rates. 
> This should match more consistently the physics of the wind driving 
> (which depends on the radiative flux, parametrized in terms of the 
> effective temperature), and also the way mass loss algorithms are 
> derived either from observations (e.g. de Jager, Nieuwenhuijzen, and van 
> Loon rates), or from numerical simulations of the wind (as in the Vink 
> case).
> 
> Best wishes,
> 
> Mathieu
> 
> On 05/26/2015 07:32 PM, Bill Paxton wrote:
> > Thank Ehsan.   And anyone else who'd like to add a comment, please do.
> >
> > bill
> >
> >
> >
> > On May 26, 2015, at 10:30 AM, Ehsan Moravveji wrote:
> >
> >> Hi Bill, hi all,
> >> I think a reasonable naming that also takes care of generality could be something
> like mass_loss_h_burning, and mass_loss_he_burning. Then whether or not one deals
> with OB stars or an RGB, the former applies, and after the core He ignition, the
> latter enters the stage.
> >> Just a suggestion …
> >>
> >> Cheers
> >> Ehsan.
> >>
> >>> On 26 May 2015, at 17:57, Bill Paxton <paxton at kitp.ucsb.edu> wrote:
> >>>
> >>> Thanks --- that is very helpful.  it looks like we're still using a scheme from
> the infancy of mesa when there were only a few options, but now it isn't a good fit
> for the range of options that have been added since then.  time for a cleanup.
> >>>
> >>> the RGB/AGB split was meant to provide a simple way for users to select different
> wind schemes for different stages of evolution.
> >>> and since the scheme could change on the fly, there needs to be a way to change
> the wind_scaling_factor too.
> >>> that is taken care of by providing separate values of scaling factor for the
> different kinds of winds.
> >>>
> >>> I can easily do the renaming to replace "eta" by "scaling factor" while keeping
> different scaling factors for different types of wind.
> >>>
> >>> Do you have suggestions for a way to replace the crude RGB/AGB by something better?
>  RGB/AGB/OB?  or what?
> >>> and please include precise details of the partitioning so that I can translate
> it into code!
> >>>
> >>> Thanks again,
> >>> Bill
> >>>
> >>>
> >>>
> >>>
> >>> On May 26, 2015, at 3:26 AM, Zsolt Keszthelyi wrote:
> >>>
> >>>> Hi Bill,
> >>>>
> >>>> thanks for your reply.
> >>>>
> >>>> I think the issue is that eta is used in different contexts with different meanings
> in the literature.
> >>>>
> >>>>
> >>>> 1. In the context of RGB / AGB stars (Reimers 1975, Blöcker 1995) eta is a scaling
> factor to match observed mass loss rates with their empirical mass loss formulas.
> >>>>
> >>>>
> >>>> 2. On the other hand, in the context of WR stars (Cassinelli 1991 and references
> therein) eta was introduced with a physical meaning, to describe the wind with the
> ratio of stellar wind momentum flux and the photon momentum flux, eta = Mdot * vinf
> / (L / c).
> >>>>
> >>>> This eta is used in the context of OB stars (e.g., Lamers & Leitherer 1993,
> Puls et al. 1996) as the performance number.
> >>>>
> >>>>
> >>>>
> >>>> Even though the idea of eta as a scaling factor is stated (and used), a user
> was looking for eta in the Vink paper, so that is why I think calling it simply 'wind_scaling_f
> actor' might make it easier for the users.
> >>>>
> >>>>
> >>>> Also my understanding is that you must set either 'RGB_wind_scheme' or 'AGB_wind_scheme'
> to apply one of the wind recipes, however the Kudritzki, Vink (OB) and Nugis & Lamers,
> Gräfener & Hamann (WR) prescriptions are not valid for these stars. This might also
> be a source of confusion since in a previous email the vink_wind_eta and RGB mass
> loss was mentioned together.
> >>>>
> >>>>
> >>>> I hope this is helpful.
> >>>>
> >>>> Cheers,
> >>>>
> >>>> Zsolt
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>> Von: Bill Paxton <paxton at kitp.ucsb.edu>
> >>>>> An: Zsolt Keszthelyi <Z.Keszthelyi at campus.lmu.de>
> >>>>> Kopie: mesa-users at lists.sourceforge.net users <mesa-users at lists.sourceforge.net>
> >>>>> Datum: Tue May 26 06:46:15 CEST 2015
> >>>>>
> >>>>>
> >>>>> 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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