[FLASH-USERS] About abundances . . .

Hi everybody,

unfortunally the flash manual is not helping me. I would like to
know what I am doing wrong - because I am sure something is wrong :)

I am setting up a problem in which I need to include a composition module.
For now it is enough to have just helium and hydrogen, so I put

        REQUIRES materials/composition/ioniz/He

in the Config file. At this point

        NUMSPECIES = 5

and the code is keeping trace of this species:

        H, e, HeI, HeII and HeIII

Good! Reading the manual (10.3.6) hydrogen and electrons are two species
- computing NUMSPECIES.

Let me now set up the mass fractions that should be, using cosmological
abundances, and a temperature of 10^8 K (full ionized medium):

        H xn(1) = smallx
        e xn(2) =
    0.76 * emass/(1.0205 * pmass) + 2.0 * 0.24 * emass/(4.002602 * pmass)
        HeI xn(3) = smallx
        HeII xn(4) = smallx
        HeIII xn(5) = 0.24 - sum(xn(1:4))

where

        emass = electron mass
        pmass = proton mass
        etc . . .

All this, supposing H is neutral hydrogen and the fraction of electrons
takes account of HII. There is no HII in the routines - at least, I have
not seen it.

But, as Mike Zingale wrote on the mailing list, the sum of all xn should
be 1.0! So, how can I take account of all the HII (ca. 76% of the mass) I
have?

Hoping to have been clear,
thank you for the answer.

Claudio.

-- 
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Claudio Dalla Vecchia        e-mail: claudio.dalla-vecchia@durham.ac.uk
Institute for Computational     web: http://star-www.dur.ac.uk/~caius/
Cosmology, South Road           tel: +44 (0)191 33 43787     linux user
Durham DH1 3LE - UK             fax: +44 (0)191 33 43645        #275369
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