[mesa-users] Fwd: adding atmosphere in structure to calculate oscillations

Bill Paxton paxton at kitp.ucsb.edu
Wed Jan 21 12:59:05 EST 2015


Hi mesa-users,

Can someone please step forward to help Tao on this.   
It might just be a matter of needing to use smaller timesteps.

Thanks,
Bill




Begin forwarded message:

> From: "ggwutao at 126.com" <ggwutao at 126.com>
> Date: January 20, 2015 12:39:28 AM PST
> To: "Bill Paxton" <paxton at kitp.ucsb.edu>
> Subject: Re: Re: [mesa-users] adding atmosphere in structure to calculate oscillations
> 
> Hi Bill,
> 
>    I'm Tao Wu. Thank you very much for your helps.  For the parameter of tau_factor, I encounter some problems. They are listed in a PDF file at the attachment.
> 
> I hope get some advices from you. 
> 
> Thanks!
> 
> Best wishes!
> 
> Tao
> ggwutao at 126.com
>  
> From: Bill Paxton
> Date: 2015-01-19 00:49
> To: WU T.
> CC: mesa-users List
> Subject: Re: [mesa-users] adding atmosphere in structure to calculate oscillations
> 
> On Jan 18, 2015, at 1:01 AM, WU T. wrote:
> 
>> Dear Bill,
>> 
>> Thank you very much for your helps. I set it as like you said. It's surely available. But there is another problem in it. When use the following settings:
>> 
>> ! tau_factor
>>       relax_to_this_tau_factor = 1.5d-4 ! tau_factor of 1 puts outer cell at photosphere.
>>          ! can go much larger or much smaller to move surface in or out from photosphere.
>>       !dlogtau_factor = 0.1 ! change log10(tau_factor) by at most this amount per step
>>      relax_tau_factor = .true. ! .false. ! gradually change tau_factor, reconverging at each step.
>> 
>> the RGB bump have larger bump comparing with without tau_factor setting.
>> The HR diagrams show in the attachments.
>> 
>> How to resolve it?
>> Thank you very much!
>> 
>> best wishes!
>> 
>> Tao
>> 
> 
> 
> 
> Hi Tao,
> 
> It is likely that different treatments of the atmosphere give different results for the bump.
> Your 1st task is to make sure that the differences remain when you increase the resolution of the runs.
> Rerun both cases with smaller timesteps and more grid points (up to 2000 or so) to make sure the results don't change.
> 
> If the results remain with much increased resolution, then you can assume the difference is coming from the treatment of the atmosphere.
> To investigate this, I'd suggest running a series of cases with a range of values for the tau factor: 1, 1.5d-1, 1.5d-2, 1.5d-3, 1.5d-4.
> What do you find -- is it a continuous change?
> 
> Then you should try some other choices for 'which_atm_option' -- e.g., in addition to 'simple_photosphere', try 'grey_and_kap' and 'Eddington_grey'.
> If you are doing Z = 0.02, then you should also try the various atmosphere tables -- there are tables for tau = 0.1, 1, 10, and 100. Try them all.
> 'tau_100_tables', 'tau_10_tables', 'tau_1_tables', 'tau_1m1_tables'.   Note that for the tables, you leave tau_factor = 1 since by selecting the table you are specifying the optical depth at the surface of the model.
> 
> When you finish this sensitivity study you'll have a made a valuable contribution!  Publish it.  
> 
> Then you be ready to answer the question of why the results for the bump depend on the treatment of the atmosphere.
> 
> Good luck,
> Bill
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
>> 
>> 
>> 
>> At 2015-01-18 00:54:13, "Bill Paxton" <paxton at kitp.ucsb.edu> wrote:
>> Hi,
>> 
>> In mesa/star, the outer edge of the stellar model is fixed at optical depth = tau_photosphere * tau_factor,
>> 
>> where tau_photosphere is determined by your choice of atmosphere model -- it is usally 2/3.
>> tau_factor is set in your inlist -- the default value is 1, but you can make it larger or smaller.
>> for example, if tau_photosphere = 2/3 and you set tau_factor = 1.5e-4 then the surface of the model will be at tau = 1e-4.
>> 
>> you can find the controls for setting tau_factor by searching mesa/star/defaults/star_job.defaults.
>> 
>> if you are working with GYRE or ADIPLS to get oscillation information, you have another alternative for going to small tau.
>> you can leave the surface of the stellar model at the photosphere and add an atmosphere to the data for the pulsation code.
>> the control for that is 'add_atmosphere_to_pulse_info' -- see mesa/star/defaults/controls.defaults.
>> 
>> good luck,
>> Bill
>> 
>> 
>> 
>> On Jan 17, 2015, at 6:25 AM, ggwutao at 126.com wrote:
>> 
>>> 
>>> Hi, everyone,
>>> 
>>>    I'm using the version of 6208 to calculate the stellar oscillations (pulse working package). I would like to add the atmosphere to the profile of structure, i.e., every structure variables vary from the center to the surface where the optival depth is very small, such as tau=1d-4.  (I want set the outer boundary at tau=1d-4.)
>>> 
>>> How to set it? I will be unequal to feel, if you give me some helps for these.
>>> 
>>> Best wishes!
>>> 
>>> Tao
>>> 
>>> ggwutao at 126.com
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>> 
>> <hr.eps><hr-1.eps>
> 

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