Magnetic impulse events and related Pc1 bursts observed by the Automatic Geophysical Observatories network in Antarctica

Magnetic field data obtained by fluxgate and search coil magnetometers inst alled at four Automatic Geophysical Observatories (AGO P1, P2, P3, and P4) and at South Pole and McMurdo in Antarctica and at Iqaluit on Baffin Island are used to study the relationship between magnetic impulse events (MIEs) and Pc1 bursts at high geomagnetic latitudes. The spatial scale sizes of MI Es are determined in the investigation of the sources of these events in th e magnetosphere. Four MIE events with simultaneous Pc1 bursts are studied. Contour plots of MIE amplitudes show the scale sizes of the examined MIEs t o be 5 degrees to 7 degrees in the magnetic latitude direction and 40 degre es to 60 degrees in the magnetic longitude direction. Temporal changes of t he ionospheric currents calculated from the fluxgate H- and D-component dat a indicate that the "convection vortices" associated with the MIEs traveled westward and decayed rapidly. An important finding is that MIE-related Pc1 bursts were observed at higher-latitude (P1, P4 near 80 degrees) and lower -latitude (P2, P3 near 70 degrees) AGO stations and South Pole Station at 7 4 degrees with different spectral structures, although the Pc1 spectral pow er was always a maximum at South Pole Station. These results imply that Pc1 bursts are excited not only in the dayside outer magnetosphere but also in the low-latitude boundary layer region.