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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 21, issue 2
Ann. Geophys., 21, 603–613, 2003
https://doi.org/10.5194/angeo-21-603-2003
© Author(s) 2003. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 21, 603–613, 2003
https://doi.org/10.5194/angeo-21-603-2003
© Author(s) 2003. This work is distributed under
the Creative Commons Attribution 3.0 License.

  28 Feb 2003

28 Feb 2003

The estimation of D-region electron densities from riometer data

J. K. Hargreaves1 and M. Friedrich2 J. K. Hargreaves and M. Friedrich
  • 1Department of Communication Systems, University of Lancaster, Lancaster, UK
  • 2Department of Communications and Wave Propagation, Technical University of Graz, Graz, Austria

Abstract. At high latitude the hard electron precipitation associated with auroral activity is a major source of ionization for the D-region, one consequence being the absorption of radio waves. Direct measurements of the D-region electron density are not readily available, however. This paper investigates the relationship between the electron density at altitudes between 100 and 70 km and the total radio absorption observed with a riometer, with a view to using the latter to predict the former. Tables are given of the median electron density corresponding to 1 dB absorption at 27.6 MHz for each hour of the day, and it is shown that at certain heights the estimates will be accurate to within a factor of 1.6 on 50% of the occasions. A systematic variation with time of day is probably associated with a progressive hardening of the typical electron spectrum during the morning hours. There is also evidence for a seasonal effect possibly due to seasonal variations of the mesosphere.

Key words. Ionosphere (auroral ionosphere) – Radio science (ionospheric propagation; instruments and techniques)

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