Whistling noises give news from atmosphere

Science Past from the issue of May 18, 1963

The atmosphere whistles while scientists work. Series of whistles — short or long, going up scale or down — keep radio scientists busy deciphering their messages of the density of charged particles in the outer regions of the earth’s atmosphere.… Generated by lightning as it strikes the earth, the radio waves are propagated back and forth in the atmosphere of the earth, in a north-south direction….