Lightning strikes twice - or more - in the same place, new paper finds

 theage.com.au  04/17/2019 17:00:00 

Lightning strikes twice - or more - in the same place, new paper finds

Lightning, it turns, can strike multiple times in the same place.

Luckily, those thunderbolts are likely to happen almost simultaneously from a specific storm cloud so people don't have to worry about avoiding a single place where lightning has struck the ground.

So-called anvil crawling lightning from storms passing over Sydney in February 2019.

So-called anvil crawling lightning from storms passing over Sydney in February 2019.Credit:Nick Moir

The possibility of multiple strikes had been "imagined" before but they hadn't been observed in detail, until now said Harvey Butcher, an emeritus professor at the Australian National University and an author of research published on Thursday in Nature.

Lightning is "one of the most dangerous and poorly understood natural phenomena", the paper said.

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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 cant 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.

"Its 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. Its big and expensive to [study lightning], so its been good [that] one could ride on the coat-tails�of the radio telescope.

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