Afternoon Pc5 geomagnetic pulsations on the Earth's surface and in the ionosphere (STARE radars)

摘要

Two cases when Pc5 geomagnetic pulsations were registered at the IMAGE Scandinavian network of stations and with STARE radars in the afternoon sector (1700-1800 MLT) during the recovery phase of the moderate magnetic storm are analyzed in detail. Using the ground-based observations, it has been indicated that classical quasimonochromatic resonance Pc5 pulsations were observed in the first case (on October 12, 1999; Kp = 5); in this case the maximal amplitude of the spectral maximum at a frequency of 2.5 mHz was registered at Φ ~ 65°. Two maximums were observed in the spectrum in the second case (on October 13, 1999; Kp = 4): ~2.5 mHz (the same maximum) and 2.9 mHz; in this case the maximal oscillation amplitude (2.5 mHz) shifted to Φ > 67°. These results were compared with the echo signal intensity simultaneously registered with the STARE Finland radar on a beam oriented along the 105° geomagnetic meridian. The spatial-temporal maps of the Pc5 pulsation amplitude latitudinal distribution (keograms), constructed based on the radar measurements in the wide range of geomagnetic latitudes (63°-70°) where the resolution was substantially higher than that of the ground-based observations, made it possible to detect two regions spaced in latitude (Φ ~ 65° and Φ ~ 67°-68°) with the simultaneous excitation of oscillations (double resonance?), between which the plasmapause projection was supposedly located.