A Study of the Interaction of Radio Waves
Proceedings of the Royal Society A
Experim ents are described in which the phenomenon o f w ave-interaction ('Luxembourg effect') is used to provide information about the height at which radio w aves of different frequencies are absorbed in the ionosphere. I t is first, dem onstrated by two crucial experim ents that the absorption mechanism suggested b y B ailey & Martyn (1934 a and b) is the true one. Measurements o f the phase o f the m odulation transferred from one w ave to the other by the non-linear absorption process in
... rption process in the ionosphere are described; and it is shown how, by measuring this phase at different modulation frequencies, it is possible to locate the region where the interaction occurs. The results of a series o f experim ents summarized in tables 2, 3 a and 3 b and figures 8 and 9 are discussed. The conclusion is reached that the frequency w ith which electrons collide w ith neutral molecules at a height o f about 85 km. is o f the order 5 x 105 sec.-1, and th at this is the height near which the main absorption of w aves of frequency 1 M cyc./sec. and 200 kcyc./sec. are absorbed at night. W aves of frequency 90 and 68 kcyc./sec. are absorbed, and possibly also reflected, below this level. W ith the approach of dawn the regions responsible for absorbing 1 Mcyc./sec. and 200 kcyc./sec. waves drift apart. The theory of Bailey & Martyn (19346) and B ailey (1937 a) is related to modern theories of ionospheric absorption and is restated w ith the standard nomenclature o f A ppleton's magneto-ionic theory. X. I n t r o d u c t i o n * I t is interesting to note th a t a 100 kW tra n sm itte r working on a frequency of 200 kcyc./sec. is capable of increasing th e tem perature of th e electrons in th e appropriate p a rt of the iono sphere by ab o u t 2 % (see § 6 (a)). D(1013) B.B.C. 68 1013 modulated GBY Rugby 01° 20' W. 52° 15' N. GBY Post Office 80 60 single sideband telephony GYA2 Cleethorpes 00° 10' W. 53° 30' N. GYA2 Admiralty 20 90-2 keyed Magnetic North Birmingham 250 km. scale F igure 2. Locations of transmitters and receivers Vol. 193. A. 21 3 . T e s t s o f t h e a b s o r b i n g m e c h a n i s m * In appendix B we discuss some com plications which m ay arise if a ground wave is received in stren g th com parable w ith th e downcoming wave. * W e are m uch indebted to D r R . L. Sm ith-Rose for supplying us w ith detailed inform ation for the occasions of our experim ents.