Questions about the cosmic ray simulation

Advanced Features and User Routines
3

Dear @chenjianqi,

  1. Note that the magnetic field specified in the GCR-SPEcard is a “special” magnetic field, which is not the same as a typical magnetic field specified with the MGNFIELDcard, and therefore cannot be plotted as the MGNFIELD. If I nonetheless find a way to plot it, I will get back to you. Generally, to plot a magnetic field defined via the MGNFIELDcard in FLAIR, you can:

    1. go to the “Plot” tab
    2. “Add” a “Geometry” plot.
    3. In the bottom right of the header, at “Type”, click and select from the drop-down menu any of the three “Field” options.
    4. Specify the coordinates for the center (e.g. z=2.2e8, x=6.02e8) and the extension (du=dv=1e6) of your plots, where your magnetic field should be located.

  2. I see in your fluscw.f routine, you are scoring each particle that arrives in your region of interest, for a total of M particles, which obviously are not normalized to anything. When you launch your simulations, you should save the number of primaries N you are using, and you would have the data as counts/primary.
    If you want to moreover normalize to counts/(m^2 s sr), please note that the <ZA>phi0465.spc files contain a distribution, where the flux is already given in particles/(m^2 s sr)/MeV. You should then compute the integrated flux from all these files, as Phi_{tot}, which will be in units ofparticles/(m^2 s sr)
    Finally, the normalization of your results should be: M * Phi_{tot} / N

  3. Please refer to the FLUKA manual, and to add more info:

    1. In FLUKA, cosmic-ray positions are generated at geographic coordinates, but their propagation is bent and filtered by the geomagnetic field model at that location. In othe words, geographic coordinates are the user-facing input, but geomagnetic coordinates are internally mapped by the model.
    2. “Why” is this so it is more a question of convention/choice, as most space weather codes use geographic coordinates as the reference grid, and then apply the geomagnetic field model on top of them.

I hope this helps,
Daniel