source code modification

[Rgh]

I understand that when I use WACCM, some upper atmospheric physics and ion sources are considered automatically, such as auroral production.
I want to modify the source code, introduce a user-defined ionization profile into the model, and extract the electron density profile.
I tried "FWHIST" and "FWSD" compsets.
Can anyone provide hints on which part of the code (which WACCM module) should be changed to include a new ionization? And how?
Is there any documentation about this modification?
Thanks

 

[Rgh]

I copied SolarForcingCMIP6_*.nc file in the inputdata to one with a different name and modified epp_ion_rates, and then changed user_nl_cam to point out to my new file.
I used FWHIST and f09_f09_mg17 for the case.
But the output electron density profile did not change by applying the new ionization profile!
Could you please comment on that?
Thanks