For the first time, scientists have clearly linked together two types of gamma-ray phenomena in thunderclouds, suggesting that weak bursts of gamma-ray activity might precede lightning flashes in certain conditions.

The two phenomena in question are weak emissions called gamma-ray glows, which last about a minute, and much shorter and more intense terrestrial gamma-ray flashes (TGFs).

Both are known to happen inside thunderclouds, depending on the various positive and negative electrical charges around them, brought on by accelerating electrons. But scientists have never fully understood how the two gamma ray phenomena work together or their link to lightning.