Time Sequence of Quasiperiodic Geomagnetic Disturbances During Substorms

Based on the data from the 2D IMAGE network and magnetic stations located in Russia, a study was conducted of a sequence of quasi-periodic geomagnetic variations with an amplitude of up to 600 nT and a duration of ~20 min that arose in the post-midnight sector during a minor global magnetic storm. It was shown that geomagnetic variations arose against the background of substorms at the same corrected geomagnetic latitude Φ' ∼ 65° sequentially one after another and moved by ~20° in longitude to the east, with a new variation occurring when the previous one moved by ~10°. It was shown that the ionospheric source of these variations is a pair of Hall current eddies, each of which has an elliptical shape with a major axis in the north-south direction. The estimated size of the ionospheric source is ~940 km in the west-east direction (each Hall current vortex is ~470 km) and ~1000 km in the north-south direction. The centers of the ionospheric sources of these variations moved eastward at a speed of ~0.8 km/s. It is shown that each geomagnetic variation is accompanied by a burst of Pi1-2 geomagnetic pulsations. It is suggested that the observed geomagnetic variations are created by magnetic fields of ionospheric current systems of microsubstorms.