Effect of Atomic Tests on Radio Noise

Abstract

Two high-altitude atomic explosions which were set off over Johnston Island in the Pacific in August 1958 appear to have had a rather pronounced effect on the radio noise as recorded at Kekaha, Hawaii. This recording station, located on the south-west coast of the Island of Kauai, is about 700 miles north-west of Johnston Island, and is a part of a world-wide chain of noise-recording stations supervised by the U.S. National Bureau of Standards. power received for a period before and after the first explosion. The usual diurnal pattern is evident during the three days prior to the blast, with the highest noise-levels recorded at night and a rapid decrease in level between 0400 and 0800 local time. In the hour following the blast, however, the noise decreased by as much as 32 db. (at some frequencies) at a time of day when it would normally be rising or holding steady. Recovery apparently occurred in a matter of hours at 13 kc./s. and 5 Mc./s., but from 51 kc./s. to 2.5 Mc./s. a changed pattern was evident for several days with levels at night much below normal. A sudden drop in the received noise-level was also noted following the second explosion on August 12; again the noise-levels at night in the frequency range of 51 kc./s.–2.5 Mc./s. continued below normal for several days, and the usual pattern of noise was considerably disturbed until about September 1.