Phase relation between Pi2‐associated ionospheric Doppler velocity and magnetic pulsations observed at a midlatitude MAGDAS station

Abstract

We examined the correlation between nighttime Pi2 pulsations detected simultaneously by a frequency modulated continuous wave (FM‐CW) (HF) radar and by a ground magnetometer, both located at a midlatitude (L = 2.05) Magnetic Data Acquisition System station. Eighty‐three Pi2 events were observed during the 43 day period from 23 September 2006 to 4 November 2006. The variations of the ground magnetic H component and ionospheric Doppler velocity ( V *) exhibited high coherence for 80% of the 83 Pi2 events, for about a half of which the H and V * variations have the same dominant frequency. For such events, V * led H by 90° in phase, in the midnight sector of 2230–0300 LT. The average Ey (east‐west electric field) amplitude derived from V * is 0.27 mV/m. The 90° phase delay was not found for the five events that were observed near dusk and dawn. The phase relation of H and V * for Pi2s in the midnight sector may be explained in terms of the radial standing structure of compressional waves, i.e., cavity mode oscillation.