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Ground-based evidence of latitude-dependent cyclotron absorption of whistler mode signals originating from VLF transmitters

Clilverd, Mark A.; Horne, Richard B.. 1996 Ground-based evidence of latitude-dependent cyclotron absorption of whistler mode signals originating from VLF transmitters. Journal of Geophysical Research: Space Physics, 101 (A2). 2355-2367. 10.1029/95JA03153

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Abstract/Summary

We report the results of the first multisite campaign using VLF Doppler receivers to detect whistler mode signals in the south Atlantic originating from VLF transmitters in the northern hemisphere. The signals at 24 and 21.4 kHz were recorded by a mobile receiver on board the RRS Bransfield during February–March 1993 and an identical system at Faraday, Antarctica. The data show that the output power of plasmaspheric ducts varies with latitude, decreasing with increasing L shell between 1.6 ≤ L ≤ 2.7. Using the HOTRAY ray tracing code, we find that the primary cause of the latitudinal variation in duct output power is absorption via cyclotron resonance with energetic electrons in the plasmasphere. The variation is due mainly to the reduction in resonant energy with increasing L shell which brings more particles into resonance with the wave. We demonstrate that ground-based observations of the absorption of whistler mode signals originating from VLF transmitters can be used as a new way of estimating the energetic electron flux between 1 and 40 keV inside the plasmasphere between 1.6 ≤ L ≤ 2.7. Typically, estimates of electron flux of 1 to 7 times greater than that reported by Schield and Frank [1970] are required to model the experimental data recorded here during nondisturbed geomagnetic conditions.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1029/95JA03153
Programmes: BAS Programmes > Pre 2000 programme
ISSN: 01480227
Date made live: 26 Oct 2016 10:27 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/514953

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