Reception of Mid-Latitude Transmissions in Northern Canada

Transmissions of WWV on six frequencies between 2·5 and 25 Mc/s have been aurally monitored hourly at four Canadian stations situated in subauroral, auroral, and polar-cap regions (Canadian Defence Research Board). In addition, WWVH transmissions on 5, 10, and 15 Mc/s from Maui, Hawaii, have been similarly monitored. The data, expressed in terms of a 0-9 signal quality index, are thus useful for describing variations in ionospheric propagation into and through the auroral zone on frequencies throughout the h.f. band. Analysis is made of the quiet-day data for both WWV and WWVH to show diurnal, seasonal, latitudinal, and frequency variations in signal quality during sunspot maximum of 1957-58. On the long paths from WWVH, orientation of the transmission paths with respect to the auroral zone apparently affects the signal quality, and reception improves going northward. A period of ionospheric disturbance is analyzed to show the differences in reception compared to quiet conditions. It is shown that conditions on different frequencies and propagation paths are closely related to the morphology of the ionospheric storm. The lower WWV frequencies (2·5-10 Mc/s) are affected primarily by polar cap and auroral zone absorption, while the higher frequencies ( 15-25 Mc/s) are affected primarily by F2 and sporadic-E critical frequencies.