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

• Main Authors: C. Jacobi, D. Kürschner
• Format: Article
• Language: deu
• Published: Copernicus Publications 2005-01-01
• Series: Advances in Radio Science
• Online Access: http://www.adv-radio-sci.net/3/427/2005/ars-3-427-2005.pdf

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.