Green Lightning
How a Chilean volcano revealed the secrets hidden in every stormcloud
UPDATED: It looks like this was just an artefact of using a filter in front of the camera lens. Click here for the full story.
Atmospheric physicist Arthur Few, from Rice University in Houston, has cracked the mystery of green lightning bolts that mysteriously appear on the edges of volcanic thunderclouds.
It’s a rare thing to spot, but Few reckons that it’s actually an extremely common phenomenon. In fact, he thinks it occurs in almost all stormclouds, but it’s normally concealed within the storm.
Several shots of the green lightning were captured by photographer Carlos Gutierrez during the eruption of the Chaiten volcano in 2008. Few studied high-resolution prints of these photos to try and find out more, and presented his results at the fall meeting of the American Geophysical Union.
In the shots, he failed to see the white-hot ionisation processes that occur at the leading tip of negatively charged lightning bolts. Instead, the green streaks must be positive channels, reversing the flow. In normal storms, this process takes place inside the clouds, but volcanic thunderclouds carry their charges on the outside due to the fragments of rock passing through the air.
“The positive streamer is the supply side that collects the negative charge that produces the lightning flash,” Few said. “We see that negative lightning flash, but we rarely see the streamer, because it is inside the cloud. But, it is being revealed when we look at the volcanic lightning.”
Few concluded that the green colour must be caused by electrically excited oxygen atoms emitting photons. The same process is what creates the green colour of the aurora borealis and aurora australis. If we could see inside thunderclouds, he believes, we’d see green lightning all the time.
UPDATED: It looks like this was just an artefact of using a filter in front of the camera lens. Click here for the full story.
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