Frequency Shifts on Whistler Mode Signals from a Stabilized VLF Transmitter

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Abstract
VLF signals received in New Zealand from NPG, Seattle, via the whistler mode are usually shifted in frequency during transit. They traverse a region of the magnetosphere which is bounded approximately by the magnetic longitudes of transmitter and receiver and which may vary in latitude during a single night over a range of several degrees.In general, signals are detected only when entry and exit points of the appropriate field lines are in darkness. They are subject to a form of geomagnetic control. The roles of ionosphere and magnetosphere as frequency shifting devices are examined, and it is concluded that the chief agency is an equatorward movement of preferred paths during the night