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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 19, issue 2
Ann. Geophys., 19, 205–217, 2001
https://doi.org/10.5194/angeo-19-205-2001
© Author(s) 2001. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 19, 205–217, 2001
https://doi.org/10.5194/angeo-19-205-2001
© Author(s) 2001. This work is distributed under
the Creative Commons Attribution 3.0 License.

  28 Feb 2001

28 Feb 2001

On the altitude dependence of the spectral characteristics of decametre-wavelength E region backscatter and the relationship with optical auroral forms

S. E. Milan1, M. Lester1, N. Sato2, and H. Takizawa3 S. E. Milan et al.
  • 1Department of Physics and Astronomy, Leicester University, Leicester LE1 7RH, UK
  • 2National Institute of Polar Research, Tokyo 173, Japan
  • 3Tohoku University, Sendai 980–8578, Japan
  • Correspondence to: S. Milan (Steve.Milan@ion.le.ac.uk)

Abstract. Observations of E region backscatter by the Ice-land East SuperDARN HF radar from the 30 minute period 2330 to 2400 UT on 13 September 1999 are presented, along with simultaneous observations of auroral luminosity from two all-sky cameras. Interferometric techniques are employed to estimate the altitude of origin of each echo observed by the radar. Under investigation is a region of backscatter which is L-shell aligned and exists in a region of low auroral luminosity bounded to the north and the south by two auroral arcs. The spectral characteristics of the backscatter fall into three main populations: broad, low Doppler shift spectra; narrow, high Doppler shift spectra; and exceptionally narrow, low Doppler shift spectra. The first two populations are similar to type II and type I spectra observed with VHF radars, respectively. These populations scatter from near the peak of the E region. The high Doppler shift population appears to exist in a region of sub-critical electric field. The third population originates below the E region peak at altitudes between 80 and 100 km. We argue that a non-coherent scattering process is responsible for this backscatter.

Key words. Ionosphere (auroral ionosphere; ionospheric irregularities)

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