Structure of disturbances in the dayside and nightside ionosphere during periods of negative interplanetary magnetic field B-z

By comparing data from a globally distributed set of high-latitude magnetic observatories with optical data in the nightside auroral ionosphere, we st udied the features of short-term activations (less than or equal to 10-15 m in) during periods of steady magnetospheric convection (SMC) observed betwe en two substorms, We found that the occurrence of local auroral and current structures stretched along the meridian to several hundreds of kilometers is the characteristic feature of activations in the nightside ionosphere, A t premidnight and night hours (2100-0100 LT) we observed auroral structures that expand rapidly equatorward (V greater than or equal to 1 km/s) from t he discrete auroral oval and become north-south aligned (N-S aurora or auro ral streamers). In the night-morning hours (0100-0500 LT) torch-like struct ures form at the poleward boundary of the diffuse auroral oval. Ionospheric currents of local auroral structures responsible for Pi3 magnetic pulsatio ns (T similar or equal to 5-15 min) are predominantly directed to the north (to the south) for auroral structures drifting azimuthally to the west (to the east). Similar auroral and current structures in the nightside ionosph ere are also observed during the expansion and recovery phase of a substorm , At the dayside during SMC events at latitudes of 75 degrees-80 degrees, m agnetic pulsations of f similar to 0.5-1.0 mHz are excited and are accompan ied by enhancements of the DPY equivalent current system. We also present o bservations which show that the N-S aurora formation is accompanied by fluc tuations of the electric field (E-y) and particle fluxes directed earthward (V-x) in the plasma sheet with a quasiperiodicity of similar to 5-15 min, On the basis of these observational facts we confirm that (1) auroral strea mers are the optical manifestation of high-speed flow bursts propagating ea rthward; (2) torch-like structures are caused by generation of magnetospher ic plasma tubes of increased pressure (in comparison with the background le vel) drifting around the Earth.