The winter anomaly as seen in the propagation of low frequency 40 kHz radio waves |
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| Institution: | 1. Department for Pharmaceutical and Pharmacological Sciences, Pharmaceutical Analysis, University of Leuven (KU Leuven), Herestraat 49, Leuven 3000, Belgium;2. Department of Chemical Engineering, Vrije Universiteit Brussel, Pleinlaan 2, Brussel 1050, Belgium;3. Department of Computer Science, Artificial Inte lligence Lab, Vrije Universiteit Brussel, Pleinlaan 9, Brussel 1050, Belgium;4. Department of Pharmaceutical Development and Manufacturing Sciences, Janssen Pharmaceutica, Turnhoutseweg 30, Beerse 2340, Belgium |
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| Abstract: | An analysis of propagation data for LF 40 kHz radio waves shows that the field strength of the sky wave is enhanced during day-time on winter anomaly days (WAD), in striking contrast to the severe attenuation of HF radio waves. This peculiar enhancement of the field strength may be ascribed to an increase in the reflection coefficient. The analysis also demonstrates that the reflection height is lower on WAD, which seems to be associated with enhancements of ionization in the D-region. Moreover, it was found that WAD are characterized by an earlier occurrence in the morning and a delayed occurrence in the evening of pronounced interference maxima and minima, respectively. |
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