A substorm is a dramatic phenomenon in the near-Earth space that is visualized as an aurora. Mostly substorms are caused by changes in the solar wind, but some of them can develop without any evident trigger. Such substorms together with undisturbed days were investigated using magnetometer and photometer data from Svalbard. Substorm precursors, i.e., specific features in 1–4 mHz geomagnetic and auroral luminosity pulsations, have been found at high geomagnetic latitudes.

Many independent observations have shown that long-period electromagnetic waves (with periods of several minutes) are preferably observed inside the auroral oval. Here we examine theoretically the possibility of Alfven wave generation by fluctuating large-scale field-aligned currents which couple outer space and the auroral ionosphere. The elaborated model indeed confirms the feasibility of an additional mechanism of long-period wave excitation which can operate at auroral latitudes.

Irregular broadband pulsations and narrow-band Pc5 waves are found to be a ubiquitous element of ULF activity in the dayside high-latitude region. To identify the ionospheric projections of the cusp, we use the width of return signal of the SuperDARN radar. The spatial structure of broadband Pc5-6 pulsation spectral power has been found to have a localized latitudinal peak, not under the cusp proper as was previously thought, but several degrees southward from the equatorward cusp boundary.