The control of the magnetosphere by power line radiation

Evidence is presented that radiated power line harmonics leak into high‐altitude regions of the magnetosphere with sufficient intensity to control the starting frequencies of chorus emissions. OGO‐3 data from three passes show that the starting frequencies of all measurable chorus emissions were within a few hertz of power line harmonics. It is also found that emissions detected over Western Europe were controlled by harmonics of 50 Hz; over the eastern United States and Canada by 60 Hz; and along the Alaska‐New Zealand meridian by harmonics of both 50 and 60 Hz. These results indicate that man‐made VLF noise plays an important role in the generation of chorus, one of the commonly observed forms of wave activity in the outer magnetosphere.