[Mesa-users] How to calculate the neutrinos flux in different radii

[Rob Farmer]

Hi,
Thanks for sharing your run_star_extras.f90

In the next release there will be history and profile column outputs for
the nuclear and neutrino energy losses per reaction. In the current RC1
there are the options:

!add_raw_rates ! raw reaction rates, reactions/second
!add_screened_rates ! screened reaction rates reactions/second
!add_eps_nuc_rates ! Nuclear energy (minus neutrino losses) released erg/s
!add_eps_neu_rates ! Neutrino losses erg/s

But these have some bugs in the accounting in the RC1 so I would wait until
we release the next version of MESA where we should have fixed these issues.

>*I cannot find an option or variable to output the number density of
electrons*

If you look in rates_def.f90:

integer, pointer :: reaction_ye_rho_exponents(:,:)=>NULL() !
(2,rates_reaction_id_max)
            ! multiply T dependent rate by Ye^a(i) * Rho^b(i)
            ! reaction_ye_rho_coeffs(1,i) is a(i)
            ! reaction_ye_rho_coeffs(2,i) is b(i)
            ! (0,0) for photodisintegrations and decays
            ! (0,1) for standard 2 body reactions
            ! (0,2) for 3 body reactions such as triple alpha
            ! (1,1) for 2 body electron captures
            ! (1,2) for 3 body electron captures (e.g., pep)

Which lets you know what pre-factors you need. This is combined with ye and
rho to get the density of electrons.

Rob


On Wed, 9 Nov 2022 at 05:27, peter zhang via Mesa-users <
mesa-users at lists.mesastar.org> wrote:

> Greetings mesa-users,
> I am using MESA  to calculate the flux of different types of neutrinos in
> different radii. There do not exist similar options in
> `profile_columns.list`.  I try to calculate the number of reactions of
> different types to represent the flux of different types of neutrinos.
>
> I have extracted the screened rates in `run_star_extras.f90`, which is
> attached in* the *attachment. The mass fractions of different isotopes
> are also acquired from the model file. The unit of screened rates is
> related to the number of reactants which has referred in the `net_def.f90`:
> ```
> ! so for a 2-body reaction, there are 2 Y factors, each with units
> [moles/gram]
> ! and the rate_screened units for such a reaction are [grams/(mole-sec)],
> ! which when multiplied by [moles/gram]^2 gives the same units as dydt.
> ```
>
> For example, the number (/cm3/s) of  reaction `pep`(p + e^- + p -> H2
> +nu_e), which is a 3-body reaction, is the product of screened rate, the
> molar density of p, and* the molar density of electrons*. The number
> density of electrons is needed but *I cannot find an option or variable
> to output the number density of electrons. Maybe there exist simpler
> methods or I misunderstand something.* Any help or clarification you
> could provide would be greatly appreciated.
>
> I am looking forward to your reply.
>
> Thank you for your time,
>
> Peter
> _______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users
>
>
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