ULF wave occurrence statistics in a high-latitude HF Doppler sounder

Abstract

Ultra low frequency (ULF) wave activity in the high-latitude ionosphere has been observed by a high frequency (HF) Doppler sounder located at Tromsù, Norway (69.7°N, 19.2°E geographic coordinates). A statistical study of the occurrence of these waves has been undertaken from data collected between 1979 and 1984. The diurnal, seasonal, solar cycle and geomagnetic activity variations in occurrence have been investigated. The ®ndings demonstrate that the ability of the sounder to detect ULF wave signatures maximises at the equinoxes and that there is a peak in occurrence in the morning sector. The occurrence rate is fairly insensitive to changes associated with the solar cycle but increases with the level of geomagnetic activity. As a result, it has been possible to characterise the way in which prevailing ionospheric and magnetospheric conditions aect such observations of ULF waves.

A statistical analysis of low‐frequency magnetic pulsations at cusp and cap latitudes in Antarctica

“…The local time dependence of spectral power and polarization presented here is the result of the statistical analysis over the entire interval of data. A separate investigation (not shown here) conducted for the different seasons showed that the results of the present analysis are permanent features at SP, largely independent of season, although somewhat more prominent during equinoxes [e.g., Rao and Gupta , 1978; Wright et al , 1999].…”

Modulation of radio frequency signals by ULF waves

“…Comparisons between ULF wave activity recorded by ground based magnetometers and associated variations in the frequency of HF waves reflected from the ionosphere have been reported by a number of researchers (Watermann, 1987;Menk, 1992;Wright et al, 1999). Most studies employ a "Doppler sounder" configuration consisting of a continuous wave (CW) transmitter/receiver system that monitors an ultra-stable frequency in the HF band.…”