Abstract
Two numerical one-dimensional and time-dependent models of the topside auroral ionosphere in the altitude range 200–3000 km are presented: they are based on two different numerical schemes to solve the eight-moment approximation of Boltzmann's equation, namely the Flux Corrected Transport (FCT) and the Method of Lines (ML). The transport equations for densities, velocities, temperatures and heat fluxes are simultaneously solved along the magnetic field lines for each constituent of the ionospheric plasma assumed to be composed of electrons and of O + and H + ions. These models, using the MSIS-86 neutral atmosphere model, include solar EUV photoionization, chemical and collisional processes between the various charged and neutral species. Steady-state results for both near-summer and winter conditions as well as for diurnal evolution are presented and compared to experimental data from the European Incoherent SCATter (EISCAT) VHF radar. It is shown that independently of the numerical scheme, the ionospheric structure is very well reproduced, given realistic external sources (solar ionization and heating, magnetospheric energy input). On the basis of the comparisons, the eight-moment approximation is validated up to 3000 km altitude. Furthermore, simulation of a diurnal evolution shows terminator effects on the enhancement of the downward F2 electron heat flow.
Published Version
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