Sounding the magnetosphere at high frequency using ducted long-delayed echoes

Observations of ducted magnetospheric echoes have been made at 1.91 MHz using a ground-based transmitter with peak power of 17 kW and pulse length of 150 μs. The echo delays were between 250 and 260 ms and sometimes showed multiple fine structure on a scale of about 200 μs. Their direction of arrival was approximately 11.5 degree north of the zenith