Evidence of thunder being a chemical explosion of air

In 1989, it was proved that thunder is not caused by the thermal expansion of the lightning channel. The present paper suggests that it is the result of an air explosion driven by the liberation of chemical bond energy from the N2 and O2 molecules. This has been confirmed by laboratory experiments with air arcs of lightning strength. These arcs are short pieces of lightning strokes and their formation is accompanied by thunder-like sonic booms.