The sun has ‘gone blank’ as solar minimum strikes

The sun has ‘gone blank’ in recent weeks (Picture Solar Dynamics Observatory)

Do not be alarmed, but the sun has just ‘gone blank’ – with the dark sunspots which usually speckle the disc vanishing for much of this year.

But it’s perfectly normal – part of an 11-year cycle where sunspots regularly fade away, bringing a period of calm.

Writing on the Watts Up With That blog Dr Tony Philips, space weather expert at Nasa, said: ‘Sunspots are becoming scarce. Very scarce.

‘So far in 2018, the sun has been blank almost 60 per cent of the time, with whole weeks going by without sunspots. Today’s sun is typical of the featureless solar disk.

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‘The fact that sunspots are vanishing comes as no surprise. Forecasters have been saying for years that this would happen as the current solar cycle, solar cycle 24, comes to an end. The surprise is how fast.’

Sunspots are strongly magnetised and crackle with solar flares – magnetic explosions which bathe Earth in X-rays and UV radiation.

But over the past couple of years, they’ve been fading – and are sliding towards a low point expected in 2019/20.

‘This is called solar minimum,’ Dean Pesnell of NASA’s Goddard Space Flight Center in Greenbelt, MD said last year. ‘And it’s a regular part of the sunspot cycle.’

While intense activity such as sunspots and solar flares subside during solar minimum, that doesn’t mean the sun becomes dull. Solar activity simply changes form.

For instance, says Pesnell, ‘during solar minimum we can see the development of long-lived coronal holes.’

Coronal holes are vast regions in the sun’s atmosphere where the sun’s magnetic field opens up and allows streams of solar particles to escape the sun as the fast solar wind.

Pesnell says ‘We see these holes throughout the solar cycle, but during solar minimum, they can last for a long time – six months or more.’

Streams of solar wind flowing from coronal holes can cause space weather effects near Earth when they hit Earth’s magnetic field.