{"id":28978,"date":"2022-02-10T00:00:00","date_gmt":"2022-02-10T00:00:00","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/?post_type=purple_issue&p=28978"},"modified":"2022-03-23T13:15:58","modified_gmt":"2022-03-23T13:15:58","slug":"whats-behind-the-uks-big-aurora-displays","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/2022\/02\/10\/whats-behind-the-uks-big-aurora-displays\/","title":{"rendered":"What\u2019s behind the UK\u2019s big aurora displays?"},"content":{"rendered":"\n

The fundamentals of astronomy for beginners<\/p>\n\n

EXPLAINER<\/span><\/h2>\n\n
\n\n

What\u2019s behind the UK\u2019s big aurora displays?<\/h4>\n\n

Melanie Windridge looks at the influence of recent increases in solar activity<\/p>\n\n

\"\"
When the solar wind is more intense, the \u2018auroral oval\u2019 of activity stretches down from higher latitudes to include the UK, like this County Durham display on 17 September 2021<\/figcaption><\/figure><\/div>\n\n

This aurora season has proved a good one so far, particularly for aurorawatchers in the UK, with numerous newspaper reports of Northern Lights seen in the UK since September. This is likely due to an uptick in solar activity as part of the solar cycle, but before we go into that, let\u2019s think about what causes the aurora in general.<\/p>\n\n

The aurora is an incredible light show caused by charged particles accelerated into our upper atmosphere. This acceleration process is driven by the Sun, so the changing power \u2013 or activity \u2013 of the Sun affects the aurora we see.<\/p>\n\n

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A NASA image of the Sun shows the turbulent activity that fuels solar wind<\/figcaption><\/figure><\/div>\n\n

When we are young we often think of the Sun as a uniform yellow ball in the sky, but look closely at NASA pictures and you\u2019ll see that the Sun\u2019s surface is anything but uniform. The Sun is made of plasma, an electrically charged gas of mostly hydrogen and helium. The surface is a bit like a boiling pan of water, with hot material welling up and cooler material dropping down. This motion is stirred up because the Sun also rotates at different speeds at its poles and equator, making for turbulent flows. Magnetic fields are generated, and are twisted into loops emerging from the surface by this rotation.<\/p>\n\n

Some of the Sun\u2019s plasma is also released into space \u2013 the Sun\u2019s atmosphere expanding out in all directions. This is called the solar wind, and it is this that drives the aurora on Earth. In addition to the ordinary outflow of particles, the Sun also throws off extra particles when twisted magnetic loops break and fling out solar matter.<\/p>\n\n

All the charged particles flowing towards us in the solar wind would be dangerous for life on Earth if we didn\u2019t have protection from our magnetic field. The electrically charged solar wind plasma has an embedded magnetic field, and magnetic fields can\u2019t cross each other, so when the solar wind hits Earth\u2019s magnetic field it is deflected around us. As it does so, it interacts with our magnetic field, transferring energy and accelerating charged particles into Earth\u2019s atmosphere to cause the aurora.<\/span><\/p>\n\n

A wider region of activity<\/strong><\/h5>\n\n

So, why do we sometimes see more aurora displays in the UK than at other times? are stronger, faster and denser, and this can cause bigger aurora <\/span>The aurora happens in rings around Earth\u2019s poles, most often seen between about 65\u00b0 and 75\u00b0 latitude. This is the region where aurorae will be generated by just everyday solar wind. But sometimes solar wind conditions displays that expand the auroral oval to lower latitudes, where they may be seen in the UK or even further south.<\/span><\/p>\n\n

\"\"
Aurora displays are caused when charged particles, streaming out of the Sun interact with Earth\u2019s magnetic field<\/figcaption><\/figure>\n\n
\"\"
As it nears solar maximum (as seen here in Solar Cycle 24), the Sun\u2019s activity increases dramatically<\/figcaption><\/figure><\/div>\n\n

Solar physicists or space weather forecasters will talk about the \u2018activity\u2019 of the Sun. This can be measured by things like sunspots on its surface \u2013 the more sunspots, the more twisted the magnetic field. It is these dark, active regions where the twisted field lines can break and throw extra matter out into the solar wind; really big examples are called coronal mass ejections (CMEs). These events are the ones that cause the biggest \u2018solar storms\u2019 and <\/span>the brightest aurora. Light from these stretches up by hundreds of metres in Earth\u2019s atmosphere.<\/p>\n\n

The Sun\u2019s activity waxes and wanes over an 11-year cycle. \u2018Solar maximum\u2019 is when the number of sunspots visible on the disc of the Sun is at its peak; it is when the solar magnetic field is most disrupted and there\u2019s an increased likelihood of solar flares and coronal mass ejections. At solar maximum, the polarity of the Sun\u2019s magnetic field flips completely and then gradually relaxes back to a minimum, undisrupted state before twisting itself up all over again.<\/p>\n\n

The last solar minimum ended in October 2020 so solar activity is now ramping up \u2013 we are now in Solar Cycle 25 \u2013 with the next peak predicted to be around mid-2025. That means we should see an increase in the frequency of space weather storms, and therefore UK aurora displays, over the coming years.<\/p>\n\n

 Turn the page to see the different types of aurora that can form, shown on a photo taken during a recent aurora display.<\/strong><\/p>\n\n

<\/div>
\n

Chasing the Northern Lights in the UK<\/h4>\n\n\n\n

Now is the time to search for one of nature\u2019s most spectacular sights<\/strong><\/p>\n\n\n\n

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A stunning aurora display captured over Caithness, appearing over the Noss Head Lighthouse on 27 January 2017<\/figcaption><\/figure><\/div>\n\n\n\n

To see the Northern Lights anywhere you need a spot looking north with a clear horizon, where there is minimal light pollution. In more populated latitudes, a good location is somewhere like a northern coastline, looking out across the sea. In general, the best places in the UK to see the aurora are the places furthest north. So, of course, Scotland is ideal, and there are some beautiful photographs of displays taken from Caithness (pictured above), the Moray coast, Aberdeenshire, Shetland and the Western Isles.<\/p>\n\n\n\n

However, for more active aurora displays where the auroral oval spreads further south, many people have luck seeing the aurora in coastal areas of Northern England such as Bamburgh or Whitley Bay in Northumberland (both known for their dark skies); north Norfolk; Northern Ireland; and even Pembrokeshire in Wales, which is barely further north than Oxford. In the UK, light pollution and clouds have the biggest impact on the visibility of mid-latitude auroral displays.<\/p>\n<\/div><\/section>\n\n

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\"\"<\/figure><\/div>\n<\/div>\n\n\n\n
\n

Dr Melanie Windridge is a plasma physicist, speaker, author of Aurora: In Search of the Northern Lights and the founder of Aurora Stories<\/p>\n<\/div>\n<\/div>\n\n

<\/p>\n\n

Photos: DAVID FORSTER\/ALAMY STOCK PHOTO, NASA\/SDO, ILLUSTRATIONS BY PAUL WOOTTON, DAN SEATON\/ESA\/ NOAA\/JPL-CALTECH, OLIVER TAYLOR\/ALAMY STOCK PHOTO<\/p>\n","protected":false},"excerpt":{"rendered":"

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