Ball lightning caused by a semi-relativistic runaway electron avalanche

•Water freezing can produce rock fractures and high electric fields on the ground.•An electric field produces a runaway electron avalanche in air.•High-energy electrons can produce light balls in the absence of thunderclouds.

Ball lightning (BL) is observed as a luminous sphere in regions of thunderstorm activity. There are many reports of BL forming in total absence of thunderclouds, associated with earthquakes and volcanoes. In this latter case, BL has been known to appear out of “nowhere”. In this work, a hypothesis on BL formation is presented involving the interaction between very low frequency (VLF) radio waves and atmospheric plasmas. High-velocity light balls are produced by ionic acoustic waves (IAWs) interacting with a stationary plasma. Several physical properties (color, velocity, and fragmentation) observed in the BL phenomenon can be explained through this model.