ZCooling Works!

Thanks to Jonathan, ZCooling is finally working. He found the last tiny error in the cooling routines, and it made the shock steady. My shock is now even closer to resembling Pat's, and I believe I understand why it's different. The issues I was having with implementing a variable mu are fixed now too. So this is the full result…Zcooling, varying mu, MHD should work but these runs are not MHD. Basically, the difference between NEQ and Z cooling is that Z will give you much more cooling below about 10,000 K or so.

Pat's is in black, mine is red

There are two discrepancies here:

  • The big one is the difference between our immediate post-shock temperatures. I believe this can be accounted for by mu. Pat's model uses a bunch of heavier species, and I calculated his mu to be about 1.26 where mine is approximately 1.0. If my simulations had an initial mu of 1.26 my post-shock temperature would be much closer to Pat's. I should be able to resolve most of this by implementing He into my module.
  • My model has a bit of a jump near 2000 K. There is also a less noticeable one at 16,500 K. This is due to the way I am using Z cooling. NEQ cooling is a combination of a few things: hydrogen excitation, ionization, recombination, and metal excitation. Z cooling is supposed to replace the metal excitation component. Right now, Z cooling and NEQ metal excitation switch on or off at the upper and lower limits of the Z cooling table. This transition just needs to be "smoothed out".


UPDATE

I fixed the two discrepancies. I could not get He ionization/recombination to work, but just adding the right amount of neutral He increased mu and brought my solution much closer to Pat's. I also "smoothed out" my solution with what I call a parabolic weight function. I don't know if that's what the math world calls it, but it worked. I will play around a little more with the He ionization/recombination, but this is already looking good enough. I'll also post the density and ionization fraction plots soon. Again, my run is red and Pat's is black.

There is probably a good reason why my run seems to flatten out at 2000 K and Pat's keeps cooling a little more. The Z cooling table that I have stops at 2000 K, and so NEQ cooling takes over below that point. I suspect that whatever Pat uses is better at cooling at such extremely low temperatures.

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