Solar wind charge-changing reactions are of paramount importance to the
physico-chemistry of the atmosphere of a comet. The ESA/Rosetta mission to
comet 67P/Churyumov-Gerasimenko (67P) provides a unique opportunity to study
charge-changing processes in situ. To understand the role of these reactions in
the evolution of the solar wind plasma, and interpret the complex in-situ
measurements made by Rosetta, numerical or analytical models are necessary. We
use an extended analytical formalism describing solar wind charge-changing
processes at comets along solar wind streamlines. The model is driven by solar
wind ion measurements from the Rosetta Plasma Consortium-Ion Composition
Analyzer (RPC-ICA) and neutral density observations from the Rosetta
Spectrometer for Ion and Neutral Analysis-Comet Pressure Sensor (ROSINA-COPS),
as well as charge-changing cross sections of hydrogen and helium particles in a
water gas. A mission-wide overview of charge-changing efficiencies at comet 67P
is presented. Electron capture cross sections dominate and favor the production
of He and H energetic neutral atoms, with fluxes expected to rival those of H+
and He2+ ions. Neutral outgassing rates are retrieved from local RPC-ICA flux
measurements, and match ROSINA's estimates very well. From the model, we find
that solar wind charge exchange is unable to fully explain the magnitude of the
sharp drop of solar wind ion fluxes observed by Rosetta for heliocentric
distances below 2.5 AU. This is likely because the model does not take into
account the relative ion dynamics and, to a lesser extent, ignore the formation
of bow shock-like structures upstream of the nucleus. This work also shows that
the ionization by solar EUV radiation and energetic electrons dominates the
source of cometary ions, although solar wind contributions may be significant
during isolated events.