On the propagation of electromagnetic waves through the atmosphere
A general method of tackling the problem of the propagation of electromagnetic waves in the ionosphere has been developed and the current methods of Appleton, Hartree, Saha, Rai and Mathur, etc., have been deduced as special cases from the general results. The different assumptions by Appleton, Hartree, Bose, Booker and Rai, as regards the condition of reflexion of the waves from the ionosphere, have been shown to be identical. A symbol-correspondence chart for the different symbols used by the different workers has been given to facilitate the understanding of the parallelism between the different methods. Polarization of the radio waves have been discussed fully.
Abnormal ionization of the E-region of the ionosphere
Abnormal ionization of the E-region of the ionosphere occurred very infrequently at Huancayo, Peru (12° south, 75° west), during nearly 8000 hours of observation. At Watheroo, Western Australia (30° south, 116° east), the effect was about 70 times as pronounced during the same period. Huancayo is on the geomagnetic equator, while Watheroo is in geomagnetic latitude about 42° south. This evidence suggests that sporadic ionization of the E-region is a function of latitude, or more probably of magnetic latitude. It is observed that sporadic ionizations appear most frequently during local summer at stations in the temperate zones. Nevertheless, because of the much greater prevalence of thunderstorms near Huancayo as compared to Watheroo, the suggestion that the effect is related to thunderstorms does not seem to be supported. There is some evidence that the abnormal ionization may be related to magnetic bays and auroras which have a similar distribution with latitude and probably originate largely in the same atmospheric region.
Weekly measurements of upper-atmospheric ionization
A series of weekly measurements of the maximum ionization content of the Kennelly-Heaviside region of the ionosphere is reported and discussed. The ionization is found to be 2.2 times as intense on a summer noon as on a winter noon, and, in general, slightly less in 1932 than in 1931. This reduction is considered to be probably due to the approach of sunspot minimum and, together with other evidence, suggests that the ionizing agency from the sun varies by as much as 60 per cent during the II-year solar period. Although ultra-violet light is accepted as the major ionizing agency, thunderstorms most probably constitute one of the subsidiary causes. The possibility that thunderstorms might cause upper-atmospheric ionization has been previously suggested by C. T. R. Wilson.