By utilizing the 50 Hz magnetic field recordings from Swarm A and C during the two weeks around the quasi-coplanar orbit configuration on 1 October 2021, we investigate the properties of kilometer-scale field-aligned currents at auroral latitudes. It is found that the kilometer-scale (0.3–5 km) field-aligned currents exhibit short-lived (<1 s) randomly appearing large current spikes. They are confined to certain latitude ranges, which depend on local time.

The study makes use of magnetic field data from the closely spaced Swarm A and C spacecraft during the counter rotating orbit phase. It allows to investigate the spatial and temporal correlation lengths of small- and meso-scale FAC structures at auroral latitudes. Stability features of small-scale FACs (10–70 km wavelength) are: temporal <18 s, correlation length <12 km. For meso-scale FACs (100–300 km wavelength) we obtain a stationarity of >40 s and correlation length >42 km.

During magnetic storms the magnetic disturbance at low latitudes becomes asymmetric, enhanced in the evening sector and reduced around morning. This has been attributed to the asymmetric ring current. Here a new 3D current system is proposed for explaining the asymmetric signal. Anti-sunward net currents at high latitude are connected at their noon and night ends to field-aligned currents that lead the currents to the magnetopause on the dawn and dusk flanks where the current closure occurs.

Extreme meteorological events such as SSWs induce variabilities in the ionosphere by modulating the atmospheric tides, and these variabilities can be comparable to a moderate geomagnetic storm. The equatorial electrojet (EEJ) is a narrow ribbon of current flowing over the dip equator in the ionosphere and is particularly sensitive to tidal changes. In this study, we use ground-magnetic measurements to investigate the semidiurnal solar and lunar tidal variabilities of the EEJ during SSWs.