Lightning strikes twice – or more


The basics of lightning have been known since at least 1752 when scientists including America’s Benjamin Franklin experimented by flying a kite into a storm.

Movement of water droplets and ice crystals generate static electrical charges with clouds, which get released as lightning – either between clouds or with the ground – when there’s a sufficient build-up.

“Most of it happens within clouds so you can’t see it with normal light,” Professor Butcher said.

The unlikely “camera” was provided by the LOFAR (Low Frequency Array) radio telescope made-up of thousands of antennas spread over 3200-square kilometres in the northern Netherlands.

It allowed for the creation of extremely high definition three-dimensional images based on the radio signal generated by the lightning.

Partly designed by Professor Butcher, the telescope’s main task was to study “radio waves that have taken the whole age of the universe to get here”.

What the researchers found when they recalibrated the telescope to study the atmosphere were so-called “needles” that store negative charge in a main lightning channel. Sometimes, not all of the charge is released in one flash, allowing for multiple lightning bolts.

“Through these needles, a negative charge may cause a repeated discharge to the ground,” he said.

Lightning kills 10 Australians a year, and it’s not yet clear whether the research will help scientists reduce the risks.

“It’s a small step, but it may turn out to be useful,” Professor Butcher said.

“People like myself get a real kick out of being able to take this telescope made for one thing and do something important in another area with it. It’s big and expensive to [study lightning], so it’s been good [that] one could ride on the coat-tails of the radio telescope.”

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