Whistler mode signals from VLF transmitters, observed at Faraday, Antarctica

• Main Authors: Smith,A.J., Yearby,K.H., Bullough,K., Saxton,J.M., Strangeways,H.J., Thomson,N.R.
• Format: Report
• Language: English
• Published: British Antarctic Survey (NERC)/British Antarctic Survey (NERC)/Department of Physics, University of Sheffield/Department of Physics, University of Sheffield/Department of Electrical and Electronic Engneering, University of Leeds/Physics Department, University of Otago 1987
• Subjects: Faraday; Antarc*; Antarctica; Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=2184; http://id.nii.ac.jp/1291/00002184/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=2184&item_no=1&attribute_id=18&file_no=1

The Doppler shift, one-hop group travel time and arrival direction of whistler mode signals from the NAA (24kHz) and NSS (21.4kHz) VLF transmitters in eastern U.S.A. have been measured in the conjugate region, at Faraday Station, Antarctica (65°S 64°W, L=2.3). Two identical narrow-band receivers of the type described by N. R. THOMSON (J. Geophys. Res., 86,4795,1981) were used. The technique enables cross-L plasma drifts and flux tube filling and emptying rates in the inner magnetosphere to be inferred continuously with a time resolution of 15min. Ducted whistler mode signals, of typical strength ∿1 μVm^<-1> from both transmitters were observed every night during February-March 1986,usually with multi-duct structure evident. Such structure was generally similar for the two transmitters, indicating propagation along a common set of ducts. This permitted the determination of the L-values of the ducts without reference to natural whistler data. Typical one hop group travel times were in the range 300-900ms and Doppler shifts in the range -500mHz to +500mHz. Most ducts could be tracked for several hours, and during the night their associated group travel times often exhibited a steady decrease followed by a steady increase, suggesting a change from inward to outward cross-L drifting under the action of east-west electric fields of magnitude ∿0.3mVm^<-1>. This drift reversal occurred at ∿02 LT and was accompanied by a rapid change from positive to negative Doppler shifts.