Long Delayed Radio Echoes,
STANFORD UNIV CALIF INST FOR PLASMA RESEARCH
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The thesis describes an experimental program carried out over a five-year period. The experiment involved transmitting a radio signal, and tape-recording the output of a receiver gang-tuned with the transmitter for the following 30 s interval. The tapes were later audited for possible long delayed echoes LDE. Although none of the possible LDE received reproduces exactly the transmitted signal, many exhibit features that seem unlikely to have been generated except by an LDE mechanism. A mechanism for producing LDE was studied which involves signal propagation in an electron plasma wave mode at very low group velocity. A weak beam-plasma instability, due to the presence of electrons precipitating into the ionosphere, is postulated as a means of offsetting collisional and collisionless attenuation of the plasma wave. Local inhomogeneities in the ionosphere cause coupling from the transmitted transverse wave to the plasma wave, and from the plasma wave to a transverse wave which can propagate back to the earth. Coupling efficiencies are estimated.
- Radiofrequency Wave Propagation
- Radio Communications