Some characteristics of electromagnetic background signals in the vicinity of one cycle per second

Near 1 cps the natural background consists of a comparatively steady, low-level, ‘white’ continuum relieved occasionally by the intrusion of either regular or impulsive geomagnetic signals, as well as by the normal occurrence of sferics. The amplitude and frequency of the intrusions depend on latitude. Characteristic, regularly repeating signal-reinforcement patterns are sometimes observed in austral and boreal regions. Such patterns are displaced in time at conjugate points by one-half their repetitive period.