Treetops Emit Ultraviolet Sparkles During Thunderstorms. Researchers Just Filmed It in Nature for the First Time

          The weather events probably cause the air around leaves to produce weak electrical discharges

https://www.smithsonianmag.com/smart-news/treetops-emit-ultraviolet-sparkles-during-thunderstorms-researchers-just-filmed-it-in-nature-for-the-first-time-180988275/

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https://en.wikipedia.org/wiki/Corona_discharge

A corona discharge is a process by which a current flows from an electrode with a high potential into a neutral fluid, usually air, by ionizing that fluid so as to create a region of plasma around the electrode. The ions generated eventually pass the charge to nearby areas of lower potential, or recombine to form neutral gas molecules.

When the potential gradient (electric field) is large enough at a point in the fluid, the fluid at that point ionizes and it becomes conductive. If a charged object has a sharp point, the electric field strength around that point will be much higher than elsewhere. Air near the electrode can become ionized (partially conductive), while regions more distant do not. When the air near the point becomes conductive, it has the effect of increasing the apparent size of the conductor. Since the new conductive region is less sharp, the ionization may not extend past this local region. Outside this region of ionization and conductivity, the charged particles slowly find their way to an oppositely charged object and are neutralized.