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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 20, issue 4
Ann. Geophys., 20, 501–509, 2002
https://doi.org/10.5194/angeo-20-501-2002
© Author(s) 2002. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 20, 501–509, 2002
https://doi.org/10.5194/angeo-20-501-2002
© Author(s) 2002. This work is distributed under
the Creative Commons Attribution 3.0 License.

  30 Apr 2002

30 Apr 2002

A case study of HF radar spectral width in the post midnight magnetic local time sector and its relationship to the polar cap boundary

E. E. Woodfield1, J. A. Davies1, P. Eglitis2, and M. Lester1 E. E. Woodfield et al.
  • 1Department of Physics and Astronomy, University of Leicester, Leicester, LE17RH, UK
  • 2Swedish Institute of Space Physics, Uppsala Division, Box 537, S-751 21 Uppsala, Sweden, and The Finnish Meteorological Institute, P. O. Box 503, Fin-00101 Helsinki, Finland
  • Correspondence to: E. E. Woodfield
  • (Emma.Woodfield@ion.le.ac.uk)

Abstract. The aim of this paper is to advance the current understanding of the spectral width parameter observed by coherent high frequency (HF) radars. In particular, we address the relationship of a frequently observed gradient, between low ( < 200 m/s) and high ( > 200 m/s) spectral width, to magnetospheric boundaries. Previous work has linked this gradient in the spectral width, in the nightside sector of magnetic local time, to the Polar Cap Boundary (PCB), and also to the boundary between the Central Plasma Sheet (CPS) and the Plasma Sheet Boundary Layer (PSBL). The present case study investigates the former by comparison with the 630.0 nm optical emission. No suitable data were available to test the second of the two hypotheses. It is found that during the interval in question the spectral width gradient is within the region of the 630.0 nm optical emission. A comparison of coherent and incoherent scatter radar data is also conducted, which indicates that values of high spectral width are typically collocated with elevated F-region electron temperatures. We conclude that the high spectral width region in the interval under study is associated with particle precipitation and also that the spectral width gradient is not a reliable method for locating the PCB.

Key words. Ionosphere (auroral ionosphere; ionospheric irregularities)

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