May’s auroras may have been the strongest in 500 years, NASA says

The dazzling aurora on May 10/11 was one of the strongest on record in the last 500 years, according to a statement from NASA.

In another claim to record status, the British Geological Survey claims the aurora in the UK is the result of the most extreme and long-lasting geomagnetic storm recorded in 155 years.

And there’s a chance it could happen again.

“We’ll be studying this event for years,” said Teresa Nieves-Chinchilla, acting director of NASA’s Moon-to-Mars Space Weather Analysis Office. “This will help us test the limits of our models and understanding of solar storms.” The space agency added that they were “probably one of the strongest aurora events recorded in the last 500 years”.

Simultaneous strikes

The solar superstorm on May 10/11 caused Polar Lights (the northern lights) to be seen as far south as Florida in the Northern Hemisphere, while Aussie glow (aurora borealis) appeared as far north as New Zealand.

NASA first detected the beginning of a solar storm on May 7, when two solar flares were detected. A staggering seven erupted over the next four days, all aimed at ejecting coronal mass—clouds of charged particles—in Earth’s direction. They traveled at different speeds and arrived at the same time.

“All of the CMEs arrived pretty much at once, and the conditions were right to create a truly historic storm,” said Elizabeth MacDonald, NASA’s Heliophysics Civil Science Lead and a space scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

Biggest since 2003

According to the BGS, May’s geomagnetic storm, caused by a series of back-to-back solar flares and the CMEs that followed them, shared characteristics with several of the largest storms since 1869, the most recent being the Halloween geomagnetic storm of 2003. Daily geomagnetic activity has been recorded since 1869, it said.

Auroras are the result of the solar wind in space – charged particles from the sun – that are accelerated down the lines of force of Earth’s magnetic field.

The Earth’s geomagnetic field is compared using readings of the horizontal magnetic field strength, which at Lerwick in the Isle of Sheland, Scotland, typically measures around 30-50 nanotesla (nT)m, according to the BGS. On the evening of May 10, they peaked at 800 nT.

ForbesIn pictures: Stunning aurora seen around the world in 2003’s best ‘Solar Superstorm’

The return of Aurora?

The sunspot that caused the flares and CME, called AR13364, is currently facing Venus, which threw a massive X12-class solar flare on May 20. This was the most powerful of the current solar cycle. As the sun rotates toward Earth, AR13364 is expected to still be active, prompting warnings of possible more powerful geomagnetic storms.

A new article published in Nature says more powerful geomagnetic storms are expected in the next year or two as the sun moves toward “solar maximum,” a peak in its magnetic activity once every 11 years.

Wishing you clear skies and wide-open eyes.

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