Lightning remains a familiar yet mysterious phenomenon. Commonplace in thunderstorms, we know the bolts equalize differences in electric charge between either two regions of a cloud or between a cloud and the ground. But still unknown is what causes air—normally an insulator—to turn into a conductor capable of transmitting up to 1 billion volts.
Astrophysicists with the Low Frequency Array, or LOFAR, a European radio telescope network, may have found some evidence supporting the idea that cosmic rays could eventually lead to a bolt of lightning. Pim Schellart, a radio astronomer at Radboud University Nijmegen in the Netherlands, and his collaborators were using LOFAR to measure cosmic rays as they streamed down from space. Normally, their computer models could predict the rays’ polarizations, but during storms, things went haywire.
Here’s Davide Castelvecchi, reporting for Nature:
Rather than throwing away this anomalous data, the team redesigned their models to include intense electric fields of the type that usually form inside thunderclouds — in which negative electric charges in a lower layer are separate from positive charges higher up. When they recalculated the polarizations using these models, the scrambled patterns matched the new simulations, the researchers report.
The cosmic ray theory was first proposed by Alex Gurevich and his colleagues at the Lebedev Physical Institute in 2002. They suggested that as cosmic rays shoot through thunderstorms, their energy may help produce, or at least kickstart, the ionization of the air along which lightning travels. While scientists have attempted to recreate these conditions in the lab, no one has come up with a definitive way to test the theory out in the world. But with more data, the LOFAR group could finally solve one of atmospheric science’s enduring mysteries.