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Abstract. By comparing data from a globally distributed set of high-latitude magnetic observatories with optical data in the nightside auroral ionosphere, we studied the features of short-term activations (_<10-15 min) during periods of steady magnetospheric convection (SMC) observed between 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. At premidnight and night hours (2100-0100 LT) we observed auroral structures that expand rapidly equatorward (V>_ 1 km/s) from the discrete auroral oval and become north-south aligned (N-S aurora or auroral streamers). In the night-morning hours (0100-0500 LT) torch-like structures form at the poleward

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