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Powerful auroras likely this week due to rare ‘backward’ sunspot

Only a tiny fraction of sunspots have reversed polarity

Vishwam Sankaran
Wednesday 10 May 2023 06:05 BST
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A rare “backward” sunspot on the Sun has released a solar flare that is expected to trigger strong auroras in the Northern hemisphere this week.

The sunspot AR3296, the magnetic field of which is reversed compared to other nearby sunspots, is expected to trigger strong geomagnetic storms on Earth and may cause stunning light shows on Wednesday and Thursday.

Only a tiny fraction of sunspots – as much as 3 per cent of them – have such a reversed polarity, scientists said.

The high energy particles discharged from the Sun are expected to cause geomagnetic storms on Earth as high-energy photons encounter the Earth’s magnetic field.

This could lead to powerful auroras – likely visible in Oregon and Virginia in the US – of an intensity similar to those seen across the world in late February and March.

The M1.5 class solar storm, first reported by Spaceweather.com on Sunday evening UTC, is reportedly travelling towards Earth at speeds of 700 and 1,100 km/s.

M class solar storms, at a scale from 1-10, are the second largest kind of flares following the X class, making M1.5 a modest flare.

The US National Oceanic and Atmospheric Administration predicts there could be mild solar storm activity on Wednesday night/Thursday morning UTC.

The exact places on Earth where the auroras would be clearly visible, however, depends on the duration of the storm.

The flare may last about six hours and could trigger strong auroras in the skies above some places.

“Arrival may thus be expected Wednesday mid to late day, but timing may change as the event is modeled and analysed further,” Space Weather Watch tweeted.

The sunspot from which the solar storm has originated is also a rule breaker, defying what is known as Hale’s Law.

This law describes the magnetic polarity associated with solar active regions and suggests that during the Sun’s current 11-year cycle, sunspots in the Northern Hemisphere should have positively charged polarities on the right, and negatively charged polarities on the left.

AR3296, however, seems to defy this law by being negatively charged on the right and positively charged on the left.

Such “backwards” sunspots may develop tangled magnetic fields that could lead to an increased chance of solar flares.

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