Numerical modelling of the thermosphere-ionosphere-protonosphere system

The results of a numerical calculation of the thermospheric circulation, the ion and electron concentrations and temperatures as well as electric fields of magnetospheric and dynamo origin are presented for solar minimum, low geomagnetic activity and spring (equinox) conditions. The results are obtained from a numerical hydrodynamical model of the Earth's ionosphere and protonosphere for the height range from 80 km to a geocentric distance of 15 R_E. The concentrations and temperature of the neutral atmosphere are computed from the MSIS-83 empirical model of the thermosphere. The effects of small electric fields on the global distributions of the thermospheric circulation, concentrations and temperatures of the charged particles in the ionosphere and protonosphere are discussed. It is shown that electric fields smaller than even 20 mV m^-1 form all the main structures of the global plasma distribution at F-region altitudes and in the protonosphere, such as the main ionospheric trough, the light ion trough, the plasmapause and 'hot spots' in the ion and electron temperature distributions.