Abstract
Abstract. Very low and low radio frequency (VLF/LF) propagation responds sensitively to the electron density distribution in the lower ionosphere (upper mesosphere). Whereas propagation paths crossing subpolar and polar regions are frequently affected by forcing from above by particle precipitations, mid- and lowlatitude paths let forcing from below be more prominent. Our observations (2009–2011) show, that the low frequency propagation conditions along the midlatitude path from Sicily to Germany (52° N 8° E) using the NSY 45.9 kHz transmitter (37° N 14° E) prove to be a good proxy of mesosphere planetary wave activity along the propagation path. High absorption events with VLF/LF propagation correlate to the well known winter time D-layer anomaly observed with high frequency (HF) radio waves. VLF/LF propagation calculations are presented which show that the radio signal amplitude variations can be modeled by planetary wave modulated collison frequency and electron density profiles. The other way around wave pressure amplitudes can be inferred from the VLF/LF data.
Highlights
Planetary waves are disturbances in the atmosphere with zonal wavelengths at the scale of the earths radius
During the Northern Hemisphere winter months planetary wavenumber one is large and variable in the mesosphere and we found further hints that the D-layer winter anomaly (unusually strong absorption of radio waves in the ionosphere, not related to solar activity (Appleton and Piggott, 1954; Lauter and Schaening, 1970; Lauter et al, 1984; Taubenheim, 1971), is correlated to planetary wave activity
We describe the data related to planetary wave activity and later on the low frequency radio propagation model
Summary
Planetary waves are disturbances in the atmosphere (with respect to wind and pressure, and temperature variations) with zonal wavelengths at the scale of the earths radius. They can be forced in the troposphere for example by topography or land-sea temperature differences but can exist as free resonant traveling waves. These waves are strongly related to global weather (formation of cyclones, anticyclones, mid-latitude depressions) and their variability is suggested.
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