Study of Pc5 Geomagnetic Pulsations on a 2D Network of Stations

Using data from the 2D IMAGE network and magnetic stations located in Russia, Pc5 geomagnetic pulsations with a frequency of ~2.8 mHz, which occurred in the afternoon sector against the background of the magnetic storm of August 27, 2014, preceded by a 5-day period with low magnetic activity, are studied in detail. In two time intervals, at the beginning of the storm and during the period of maximum magnetic activity, instantaneous 2D distributions of Pc5 magnetic field amplitudes on Earth’s surface are plotted. It has been found that the ionospheric sources of Pc5 (vortex Hall currents) have an elliptical shape with a larger axis in the south–north direction. At the beginning of the magnetic storm, a single burst of Pc5 pulsations was detected, the center of the source of which was located at the geomagnetic latitude ~67.5° (L ~ 6.8 R_E) and moved westward with a velocity of ~0.7 km/s. The estimated size of this ionospheric source is ~150 km in the west–east direction and ~330 km in the south–north direction. During the maximum of the magnetic storm, Pc5 pulsations are produced by two ionospheric sources following each other. These ionospheric sources have a more elongated elliptical shape with axes of ~250 km in the west–east direction and ~670 km in the south–north direction. The centers of these sources were shifted by 4° to a more southern geomagnetic latitude ~63.5° (L ~ 5 R_E) and moved westward with a velocity of ~1.7 km/s. Estimates of the size of the two-time magnetic field tube in which the resonance MHD waves have been generated and its velocity in the equatorial plane of the magnetosphere are presented.