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Radar speed detectors are used by police to measure a car's speed. Using similar
radar-like pulses the IMAGE satellite probes the invisible plasma near Earth. As it
passes through the plasmapause, echoes from IMAGE's powerful radio transmitter can be detected.
IMAGE scientists believe these echoes are guided by plasma 'ducts'. These ducts act like
invisible pipes that channel the radio signals along Earth's magnetic field from pole to pole.
(2002: D. L. Carpenter, M. A. Spasojevic, T. F. Bell, U. S. Inan,
B.W. Reinisch, I. A. Galkin, R. F. Benson, J. L. Green,
S. F. Fung, and S. A. Boardsen)