Simultaneous electric and magnetic field observations of Pcl-2, and Pc3 pulsations

This paper presents results from a combined analysis of ULF fluctuations in the geoelectric and geomagnetic fields. Data were obtained at South Pole station during the 1985-1986 South Pole Balloon Campaign. Magnetic field perturbations were measured by the two-axis induction or "search coil" magnetometer at South Pole station. Vector electric field data were obtained by a standard double-probe experiment on the balloon payloads. The objective of this study is to investigate the relationship between the electric and the magnetic components of geomagnetic micropulsations in the Pc1-3 frequency bands (0.01 to 0.5 Hx). The entire 468-hour database of the balloon campaign has been searched for examples of strong discrete magnetic micropulsation emissions in these bands. The two best days were found to be January 7 and 8, 1986. Two emissions were seen on both days, a Pc3 emission between 30 and 40 mHz that extended for about 3 hours on either side of magnetic noon and a Pc1-2 emission that started around magnetic noon and lasted for several hours. The amplitude histories of the emissions were found to be roughly comparable when account was taken of the effect of varying precipitation on the ionospheric conductivity. The two components of the magnetic field did not show significant coherence. Consequently, little coherence was expected or found between the electric and magnetic components. An ionospheric transmission model has been used to interpret the observed BIE ratio in terms of the horizontal wave number of the source. The wave number that was inferred for the Pc3 emissions implies a phase speed roughly equal to the phase speed of simultaneous traveling convection vortex events.