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

摘要

We examined the correlation between nighttime Pi2 pulsations detectedsimultaneously by a frequency modulated continuous wave (FM-CW) (HF) radar and by aground magnetometer, both located at a midlatitude (L = 2.05) Magnetic Data AcquisitionSystem station. Eighty-three Pi2 events were observed during the 43 day period from23 September 2006 to 4 November 2006. The variations of the ground magnetic Hcomponent and ionospheric Doppler velocity ( V~*) exhibited high coherence for 80% ofthe 83 Pi2 events, for about a half of which the H and V* variations have the samedominant frequency. For such events, V~* ledHby 90° in phase, in the midnight sector of2230-0300 LT. The average Ey (east-west electric field) amplitude derived from V~* is0.27 mV/m. The 90° phase delay was not found for the five events that were observed neardusk and dawn. The phase relation of H and V~* for Pi2s in the midnight sector may beexplained in terms of the radial standing structure of compressional waves, i.e., cavitymode oscillation.