Combined world-wide neutral air wind and electrodynamic drift effects on the F2-layer

Abstract

Three time-varying solutions of the world-wide continuity equation for electrons in the F2-region are obtained under equinoctial conditions of symmetry. The effects of production, loss, diffusion, electrodynamic ‘ E × B ’ drift and neutral air winds are taken into account. The three solutions correspond to various combinations of an ‘ E × B ’ drift of amplitude 20 m/sec −1 and a meridional neutral air wind of maximum magnitude 100 m/sec −1. The ‘ E × B’ drift chosen is simple harmonic, being upwards during the day and downwards at night. The meridional wind chosen is simple harmonic, being polewards during the period 4.5–16.5 hr LT and equatorwards for the remaining period; it varies with latitude, has a latitudinal maximum at ± 45° and vanishes both at the equator and at the poles. The results show that, at midlatitudes, wind effects alone can explain the observed diurnal variations in N m F2 and that at equatorial stations winds combined with ‘ E × B ’ drifts can explain the observed noon bite-out and the post-sunset anomalous enhancement of N m F2. The ‘ E × B ’ drift produces a realistic equatorial anomaly and is responsible for the noon bite-out observed at the dip equator. Neutral air winds may be responsible for the maintenance of the night-time equatorial F2-layer, for the considerable day-to-night change in h m F2 and for a night-time anomalous behaviour in h m F2 which is similar both to that observed in the winter hemisphere and to h' F2 observed during equinoctial months. Thus it is shown that neutral air winds combined with ‘ E × B ’ drifts produce realistic ionospheric models.