Whistler (radio)

A whistler is a very low frequency electromagnetic radio wave generated by a lightning strike, typically in the range of one to thirty kilohertz. After a lightning discharge, the resulting radio impulse can travel along one of Earth's magnetic field lines from one hemisphere to the other, passing through the ionosphere and magnetosphere; because lower frequencies travel more slowly through this plasma environment than higher ones, the wave disperses and is heard, when converted to audio, as a descending tone that can last several seconds. British radio operators in the First World War, who first noticed the effect on their equipment and likened its sound to a whistle or an incoming shell, gave the phenomenon its name. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/