1. Electromagnetic radiation, caused by natural electrical disturbances in the atmosphere, which interferes with radio systems; also known as atmospherics or strays.
2. The radio frequency electromagnetic radiation originating, principally, in the irregular surges of charge in thunderstorm lightning discharges.

Atmospherics are heard as a quasi-steady background of crackling noise (static) on certain radio frequencies; such as, those used to broadcast AM radio signals.

Since any acceleration of electric charge leads to emission of electromagnetic radiation, and since the several processes involved in propagation of lightning lead to very large charge accelerations, the lightning channel acts like a huge transmitter, sending out radiation with frequencies of the order of 10 kHz.

1. Electromagnetic radiation produced by natural phenomena; such as, lightning.
2. Atmospheric disturbances of electrical origin causing interference with communication in wireless telegraphy, television, etc.
3. Atmospheric conditions caused by electromagnetic disturbances; especially, as they affect radio transmission.