DOPPLER-SHIFT PULSATIONS ON WHISTLER-MODE SIGNALS FROM A VLF TRANSMITTER

Whistler mode signals from the NAA transmitter (24 kHz) received at Fa raday, Antarctica are processed to obtain the Doppler shift at a much higher time resolution than has previously been possible. This has all owed the observation of pulsations of about 13 mHz frequency which are believed to be associated with hydromagnetic waves in the magnetosphe re. The pulsations are observed separately on signals with a number of discrete group delay features that can be interpreted as individual w histler ducts. Using the measured pulsation phase over the array of du cts the phase velocity and wave normal direction of the hydromagnetic wave in the equatorial plane are estimated. The direction of propagati on is consistent with a source on the dayside magnetopause. The associ ation between whistler mode Doppler shifts and hydromagnetic waves has been reported before but not, as far as we are aware, using an experi mental technique that allows measurements on individual ducts in order to determine the direction of propagation of the hydromagnetic wave. (C) 1996 Elsevier Science Ltd