[mesa-users] mesa-users Digest, Vol 33, Issue 2

[Josh Shiode]

I've had quite a bit of experience with this, and second Bill's suggestion. 

The PGSTAR convection and profile (displaying entropy) windows can 
be useful for investigating this. 

In my experience, these events result from intermediate convection zones, i.e., 
one that pops up near maximum extent of the core convection zone (which is 
receding with time). These intermediate zones sometimes grow or just 'move' 
in mass coordinate in towards the core. When the two zones touch, this 
intermediate zone brings in fresh hydrogen, which quickly convectively mixes 
and causes you to see this spike in center_h1. These can be pretty effectively 
shut off by turning off 'convective undershooting.' Try setting 

overshoot_f_below_nonburn = 0

If what I describe above is the cause, that should fix it. That said, your mileage 
may vary, and there are so many convection parameters that this may not solve 
your problem. If just this fails, try setting all overshoot to zero and using the 
Ledoux criterion and semiconvection instead. 

And then let us know what works!

--Josh


On May 1, 2012, at 9:56 AM, mesa-users-request at lists.sourceforge.net wrote:

> From: Bill Paxton <paxton at kitp.ucsb.edu>
> Subject: Re: [mesa-users] central hydrogen sudden increase
> To: andres suarez <asuarezm at ucsc.edu>
> Cc: mesa-users at lists.sourceforge.net
> Message-ID: <1CB8584A-8B9C-4C71-A0D4-23BDCAC27CA9 at kitp.ucsb.edu>
> Content-Type: text/plain; charset="us-ascii"
> 
> Check to see what the central convection zone is doing.
> I expect that the jump in center H is because convection
> has reached outward to a fresh supply of H and brought
> it down to the center.  So now your question becomes
> why do convection zones grow and shrink.  Is it a bug?
> Is it physical?  Have fun.
> 
> -B