Lightning Secrets: How Trees Glow Before a Storm

When the air feels itchy and your hair jumps, it might mean a storm is coming. Scientists noticed a faint blue light that sometimes appears on tree tops during heavy weather. This glow, called corona discharge, is a tiny electric spark that can be seen when the sky splits into two layers of charge. The upper layer is positive, while the lower one is negative. Because opposite charges attract, electricity on the ground pushes toward the sky’s opposite charge. Above the forest canopy, the electric field is stronger. Occasionally this force connects the ground and sky, producing a bright flash that can be captured with special ultraviolet cameras.

This is the first time researchers have documented corona discharge on trees in a North Carolina forest. In laboratory tests, the tips of leaves and needles show signs of burning when exposed to this spark. It suggests that trees might have evolved ways to cope with or even benefit from these electric events. Some scientists think that similar sparks could occur inside thunderclouds, possibly at the tips of ice crystals. Exploring this idea is a planned future project.

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