The three-dimensional global numerical model CHARM-I: The incorporation of processes in the ionospheric D-region

We describe the three-dimensional numerical global photochemical model CHARM-I (CHemical Atmospheric Research Model with Ions) and the results of numerical calculations of global distributions of neutral and charged atmospheric trace gases (in the height range of up to 90 km), such as ozone, nitrogen oxides, electrons, and positive and negative ions. This model is an improved version of the CHARM three-dimensional photochemical model of neutral components with additional reactions with the involvement of ions (a total of 200 photochemical reactions). The model incorporates UV-radiation fluxes on the Lyman-α line and galactic cosmic rays as ionizing factors. The neutral components are calculated with the method of “chemical families” and the concentrations of charged components are calculated by the electroneutrality condition at each time step. The spatial transport of chemically active species is described in the model by the Prather scheme. The developed model makes it also possible to take into account solar flares and particle precipitations in the ionospheric D -region.