sentences:  Another describes how injection of a low frequency radio signal into the magnetosphere causes a radio quieting of the natural noise that's associated with these frequencies.Another paper showed that the alternating current power grids in North America (60 Hz) and Europe (50 Hz) affect auroral chorus emissions.Helliwell was a fellow of the Institute of Electrical and Electronics Engineers and the American Geophysical Union, and a member of the American Association for the Advancement of Science and the United States National Academy of Sciences.