A vocabulary of landscape — a landscape of words
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sferics
Sferics are the bursts of radio noise produced by lightning. Every stroke radiates a broadband pulse that travels enormous distances by bouncing between the ground and the ionosphere, so a receiver anywhere can hear strikes from the other side of the world. On an ordinary AM radio they are the crackle during a storm. Networks of receivers now locate strikes worldwide by timing when the pulse arrives at each station.
Etymology
The word is a clipping of atmospherics, which is what the noise was called when radio operators first met it and assumed the atmosphere itself was to blame. Dropping the front of a long technical word is a standard piece of radio-trade shorthand, and the shortened form is now the formal term in the literature.
Notes
Some sferics travel out along the earth’s magnetic field lines into space and come back to the opposite hemisphere, and the trip disperses the frequencies so the high notes arrive before the low ones. Played through a speaker, this produces a descending whistle lasting a second or so, and the phenomenon is called a whistler. It was heard on field telephone lines in the First World War and puzzled over for decades before anyone worked out the path.