Fast solar winds linked to increase in lightning strike rates on Earth


Torrents of high-energy particles in solar winds may be increasing lightning-generating thunderstorms here on Earth, British researchers say.

While it has been known that lightning on Earth can be triggered by cosmic rays coming from outer space, the new study by scientists at the University of Reading is the first to link the storm phenomenon to energetic particles ejected toward Earth from the surface of the Sun.

The exact process behind the finding remains unknown, they admit, although they suggest electrical properties in the atmosphere may be altered as charged particles in solar wind impact on it.

"Our main result is that we have found evidence that high-speed solar wind streams can increase lightning rates," study lead author Chris Scott says. "This may be an actual increase in lightning or an increase in the magnitude of lightning, lifting it above the detection threshold of measurement instruments."

Spacecraft can track approaching solar winds, suggesting a useful source of data for weather forecasters that could help predict hazardous storm conditions in advance, the researchers said.

The wild weather linked to solar storms can last as much as a month once the stream of particles first hits the Earth's atmosphere, they said.

Analyzing data gathered in the United Kingdom, the Reading researchers found, on average, slightly more than 400 lightning strikes during the 40 or so days following the arrival of high-speed solar winds, as opposed to an average 321 strikes during the same period preceding their arrival.

The looked at data on lightning strikes between 2000 to 2005, was then compared with information from a NASA spacecraft which measured solar winds from its position between the Earth and the Sun.

The peak in lightning strikes occurred from 12 to 18 days after the solar wind's arrival, they noted.

Although they used data from the United Kingdom, the resultant effect is almost certainly global, they said.

"We looked at Northern Europe because that's where the detection system is located, but lightning in Africa is much more intense than over Europe," Scott said.

Lightning strikes are responsible for around 24,000 deaths globally each year, a 2008 study found.

Any additional understanding of lightning such as that provided by the new study, with the possibility of more advance warning of strikes, is useful, he said.

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