IONOSONDE SIGNATURES OF PC1 PULSATIONS

The first observations of the signatures of Pc1 pulsations in ionosonde echo data are reported. Oscillations are frequently observed in Doppler velocity, echo amplitude, group range and skymap echo-location position, and are clearly associated with simultaneous Pc1 geomagnetic micropulsations with a similar frequency. These oscillations, recorded at the sub-auroral Antarctic station of Halley (76-degrees-S, 27-degrees-W, L approximately 4.2), occur in either or both E- and F-region echo time series during a wide range of ionospheric conditions. Focusing of the ionospheric echoes due to the compressional action of the hydromagnetic wave is suggested as a possible mechanism.