My vote is electrostatics.
They act a bit like RF when they discharge, as obviously the discharge is quite fast.
When I worked at a MF AM Broadcast site, the 400+foot "vertical radiator" would often become charged, &, despite the nice big choke at the base of the mast, which went straight to ground, would arc over at the protective "horn gap".
When this happened, the transmitter would be unaffected, &, in fact, would maintain the arc until it travelled out to the end of the "horn" & extinguished.
During this time, the programme material would be loudly audible, due to the "singing arc" phenomenon.
A lightning strike, either direct, or nearby would cause the transmitter to "grunt" & recycle, so the resultant arc didn't last as long.
Another interesting thing was when I worked at Kalgoorlie.
At. the MF site, we had recently upgraded the remote alarm system, which extended either a "loop" or an "open" to another site to indicate whatever fault was active.
The previous system used a bunch of "Post Office" relays to send these indications, but these had bern replaced with boards fitted with "reed relays", which were much more compact & freed up room on the rack.
We were surprised to find many of these reed relays failing in service, & investigated the reason.
It turned out that as the ground was hard in Kalgoorlie, the phone lines were not buried quite as deep as in other places.
Either electrostatic charges prior to, or nearby strikes during a storm, produced enough volts across the reed contacts to arc, welding them together.
The old "Post Office" relays would have "shrugged", said "Yeah, whatever", & gone on with their business.