sferic

“But the right kind of signals are generated naturally by lightning strikes, which cause the emission of "atmospheric" ( "sferic" or "spheric") radio pulses.”

The Register

“It could be informed of the positions of the strikes over LF comms by a single specialised surface base station, similarly far off, and thus calculate its own position from sferic data coming in from several directions. reportedly the subject of a small DARPA feasibility investigation last year.”

The Register

“The same electromagnetic pulses can be registered in the event of elevated sferic frequencies or nuclear electromagnetic pulses stemming from elevated sun activities, and from our perspective this is another reason why it is undertaken to repel these sferic frequencies with the help of toxic substances, like aluminium oxides and barium-chlorides so as to protect semiconductor technologies. ”

Signs of the Times