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

• Published in: Annales Geophysicae
• Main Authors: D. M. Wright, T. K. Yeoman, T. B. Jones
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 1999
• Subjects: Science; Q; Physics; QC1-999; Geophysics. Cosmic physics; QC801-809; Norway; Tromsø
• Online Access: https://doi.org/10.1007/s00585-999-0749-2; https://doaj.org/article/b09eabb974da4c71921d1657ef0f34f5

Ultra low frequency (ULF) wave activity in the high-latitude ionosphere has been observed by a high frequency (HF) Doppler sounder located at Tromsø, 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 findings 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 affect such observations of ULF waves. Key words . Ionosphere (auroral ionosphere; ionosphere -magnetosphere interactions) · Magnetospheric physics (MHD waves and instabilities)