A HIGH-RESOLUTION MODEL FOR THE IONOSPHERIC F-REGION AT MIDLATITUDE AND HIGH-LATITUDE SITES

We have constructed an ionospheric model which yields the evolution of the F-region at arbitrary mid- and high-latitude sites in terms of the electron density, n(e), and the magnetic field parallel ion drift, v(parallel-to). These quantities are obtained by the time-dependent solution of appropriate coupled continuity and momentum equations. The densities of the major ion species (O+, NO+, O2+, N2+) can be deduced. The numerical model setup, allowing almost arbitrary resolution in an efficient manner, is basically magnetic field-aligned, but electric-field induced perpendicular convection is fully taken into account whereby no vertical plasma stratification is assumed. A comparison of model results with a representative 1 1/2 day set of EISCAT data was carried out in a case study, mainly in order to demonstrate the validity and usefulness of the model. This aim was achieved, as the model predicted the evolution of n(e) over all F-region heights and the entire time range within about +/- 30% uncertainty, without sophisticated parameter adjustments. v(parallel-to) was also predicted quite satisfactorily. General further indications of our hitherto results are: the recent proposal to increase the presently available theoretical O+ - O collision frequencies by a factor of approximately 1.5 is supported. The recent neutral wind model HWM-90 appears to be appropriate for altitudes below the F2-peak but does considerably overestimate the nighttime equatorward wind magnitude in the F2-layer in our case study. The MSIS-86 model provides a reasonable quantitative neutral atmosphere input, but possibly tends to underestimate atomic/molecular concentration ratios during distinctly quiet conditions, as prevailed in our case. Neutral wind and ionosphere-plasmasphere exchange flux effects on the ionization merge in an almost inseparable way, confirming recent results of other authors. A set of merely six reactions can satisfactorily account for the F-region ion loss chemistry, enabling a convenient photochemical balance formulation for n(e). Vibrationally excited N2 has to be accounted for in the auroral oval for quantitative studies. Horizontal plasma gradients are non-negligible even in the presence of merely moderate electric fields. Finally, future model extensions as well as forthcoming and likely applications are addressed which the model may handle with a quality not possible with other current ionospheric models.