Diffuse auroral zone

A comprehensive experiment has been carried out aimed at the investigation of the polar boundary of the principal ionosphere gap. The data are obtained with the help of the meridional chain of ionosphere stations with the addition of antennas for the inclined sounding from two subauroral stations (Yakutsk, invariant latitude Λ0=55 deg, 8 and Batagay, Λ0=61 deg, 1) together with the simultaneous measurements from the ''Oreol-2'' satellite of auroral particles of the diffusive zone of the intrusion within the wide range of energies. The quantitative and spatial conformity is discovered between the ionization jump on the polar boundary of the gap and the ionization of the F-layer with soft electrons with the energies of 0.2-2 keV of the diffusive zone of the intrusion injected on the internal boundary of the plasmic layer during the substorm. The duration of the existence of the additional ionization after an isolated outburst of the substorm is 1-3 hours; it is accompanied by the decrease of the level of ionization o n the edge of the diffusive zone and inside it. Under these conditions the slow shift of the ionization boundary to the equator should be attributed to the daily rotation of the station under the almost motionless structure of the plasmic layer and its projection to the ionosphere. At lasting intensive perturbations the boundary of the ionization with soft electrons is lowered to subauroral latitudes Λ0 < or approximately 60 deg. When the station of the reverse-inclined sounding is located near the gap centre (Λ0 approximately 60 deg) the detection of critical inclined reflections from the ''ionization wall'' on the polar boundary of the gap is essentially simplified which allows to perform its practically continuous recording