Dynasonde observations of Pc1 propagation in the ionosphere

Ground-based observations of Pc1 geomagnetic pulsations propagating in the ionosphere over Halley (76 °S, 27 °W, L ~ 4.2), Antarctica, have been made. The direction of propagation of the Pc1 waves in the ionospheric duct has been calculated from the orientation of the geomagnetic pulsation polarisation ellipse derived from data recorded by a triaxial ULF receiver. These have been compared with the geographic bearing of simultaneous echolocation oscillations, at the same Pc1 frequencies, in HF ionospheric sounding data obtained using a dynasonde. Many of these bearings are found to show reasonable agreement with the direction of propagation of the Pc1. The analysis suggests that the oscillations observed in the echolocation data are the consequence of wave-like disturbances in the ionosphere directly linked to the Pc1 propagation. Discrepancies can be explained in terms of changes in the pulsation polarisation ellipse dependent upon the distance of the observer from the ionospheric source.