Fig. 8. Computed vertical concentration profiles for neutral species and positive ion species respectively at noon on May 14 at 38° latitude off Wallops Island, VA, 30 min before the Skylab I launch. ion transport equations incorporate effects of the electric and magnetic fields. The transport equations are described in more detail in Appendix B. d. Time-varying temperatures. The temperature array is generated as a function of altitude and time based on fits to standard empirical models, scaled to the assumed exospheric temperature, which is specified as an input variable. Daytime electron and ion temperatures are generated with a set of algorithms that relates them to the neutral temperatures and local electron concentrations. The chemical rate coefficients, diffusion rates, and vertical winds are computed from these temperatures. e. Cosmic rays, precipitating electrons, and He ' 304-A radiation. These ionization sources are included because of their importance in the D-layer and the night-time E-layer. f. Diffusion of H+from the protonosphere. To maintain the night-time F2 layer in the computations, it is necessary to provide a persistent flux of H+ at the upper (700-km) boundary. Other species are allowed to simply diffuse through the boundary in accordance with their varying hydrostatic equilibria. g. Horizontal winds. Tidal-wind velocities and E-fields are specified as functions of altitude, latitude, and time, based on models fit to experimental observations (7-12). The wind model is described in Appendix B. One-dimensional codes and computations of the normal ionosphere The two-dimensional code can be operated in a one-dimensional mode for computing the structure and diurnal variability of the normal ionosphere. The onedimensional computations are used to furnish starting conditions for the two- dimensional rocket exhaust injection problems. The two-dimensional code (or its one-dimensional version) provides a reasonably accurate description of the normal ionosphere above 90-km altitude (E- and F-layers). However, its 28-species chemistry model is not adequate for the D-layer (below 90 km). To cope with the D-layer chemistry, and to model the E- and F-layers
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