Ionospheric effects on the transmission of ultralow-frequency plasma waves.

Measurements of magnetospheric ultralow-frequency plasma waves (period tau, approximately 18 to 150 seconds) on the ground under continuous daylight conditions in the Antarctic and under alternate day-night solar illumination at the conjugate station in Quebec indicate a significant local time dependence in the transmission properties of the ionosphere for waves of these periods. When the Antarctic station is compared with the Quebec station, the tilt (with respect to the ionosphere) of the orientation plane of the waves is observed to be larger at local noon than at local night.