Articles | Volume 3
Adv. Radio Sci., 3, 427–430, 2005
https://doi.org/10.5194/ars-3-427-2005
Adv. Radio Sci., 3, 427–430, 2005
https://doi.org/10.5194/ars-3-427-2005

  13 May 2005

13 May 2005

Long-term Measurements of Nighttime LF Radio Wave Reflection Heights over Central Europe

C. Jacobi1 and D. Kürschner2 C. Jacobi and D. Kürschner
  • 1Institute for Meteorology, University of Leipzig, Stephanstr. 3, 04103 Leipzig, Germany
  • 2Institute for Geophysics and Geology, University of Leipzig, Collm Observatory, 04779 Wermsdorf, Germany

Abstract. The nighttime ionospheric absolute reflection height of low-frequency (LF) radio waves at oblique incidence has been measured continuously since late 1982 using 1.8kHz sideband phase comparisons between the sky wave and the ground wave of a commercial 177kHz LF transmitter. The dataset allows the analysis of long-term trends and other regular variations of the reflection height. Beside the clear signal of the 11-year solar cycle a quasi-biennial oscillation is visible in LF reflection heights, which is correlated to the equatorial stratospheric wind field. A long-term decreasing reflection height trend is found, confirming results from other measurements and theoretical estimations. The results can be interpreted as a long-term decrease of the height levels of fixed electron density in the lower E region, reflecting a long-term cooling trend of the middle atmosphere.