张郸
2019-09-15 03:16:02

Parts of Britain revelled in a celestial light show on Wednesday night as the northern lights were clearly visible in northern England, north Wales, and Scotland.

The aurora borealis – usually caused by solar particles colliding in the atmosphere – is a more common occurrence much further north around the Arctic circle.

Northern lights over the Eden Valley in Cumbria. Photograph: Tom Hughes/Rex/ Shutterstock

But the improved chances of a sighting in Britain are due to the combined effect of a “coronal hole” near the sun’s equator, which had aligned with Earth and was sending high-speed solar winds to buffet the planet, and the time of year.

A Met Office spokesman said: “We are now in a period, lasting a few weeks, where these two factors are working together to increase the chances of geomagnetic disturbances, which in turn bring with them the aurora.

“The strength of the disturbance directly relates to how far south the aurora is visible, or how far north if you are in the southern hemisphere, and of course you need clear skies to see it.

“The season of the year has an influence. The science behind this is not fully understood, but the two equinoctial periods in spring and autumn tend to produce an increase in aurora compared with winter and summer.”

Stuart Stevenson from Clyde Valley, tweeted:

Stuart Stevenson (@StevensonStuart)

Just had the most magical of nights, hunting in . By far the best display I've ever seen in Scotland!

Also on the social media network, Gareth Brooks described the show over Inverness as “”.

The British Geological Survey says , with huge amounts of charged particles thrown out into space.

These particles sometimes travel towards Earth, where they are captured by its magnetic field and guided towards the geomagnetic polar regions.

On their way down these particles are slowed down by Earth’s atmosphere, which acts as a shield. The charged particles collide with gas molecules in the atmosphere and the energy released is given off as light. A range of blues, greens, yellows and reds are usually observed in the aurora.

Under normal conditions the northern oval lights cover Scandinavia, Greenland, Alaska, Canada and Russia. The southern oval covers the Antarctic regions. With increasing geomagnetic activity the ovals widen and spread, so that during periods of high geomagnetic activity it becomes possible to see aurora further south in the UK.