The Aurora Borealis: Lights in the Midnight Sky

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Nobody can deny that the Aurora Borealis is one of the most majestic sights that nature can conjure on this planet. Aurorae seem to be the perfect marriage to an already captivating night sky, capturing the imaginations of people all around the world with stunning tendrils of light, which dance across the midnight zodiac. But how can we predict when we will see one in the UK? Of course, if you were to travel to the Scottish highlands, you’d have a much better chance than if you were in Cornwall, for example, yet even then it is a rare sight to merely glimpse an aurora anywhere in the UK. This leads to a different line of questioning: How can we predict aurorae activity?

The sun operates on an 11-year activity cycle; every 11 years, more sun-spots appear, which leads to more gas and plasma being thrown out into our solar system. Hence, more aurorae. But this still doesn’t provide any short-term predictions. Thankfully, this question can be answered by studying the activity of the aurorae themselves, which is why AuroraWatch UK is one of the most important scientific endeavours in this regard. AuroraWatch UK operates as part of SAMNET, ‘The UK Sub-Auroral Magnetometer Network,’ which combines masses of data gleaned from roughly a dozen stations, of varying sensitivity, located in countries such as Russia, Holland, Iceland and the UK, to provide live information about what is happening up in the magnetosphere (a large magnetic field, enshrouding our planet).

Professor Jim Wild, a foremost expert in the field of space-weather and Professor of Space Physics at Lancaster University, explained that ‘an array of scanners are used which measure the geomagnetic activity in the upper atmosphere, super-imposing geomagnetic disturbances over the earth’s regular magnetic field.’ Furthermore, ‘they measure the space environment around the planet, when there’s a lot of geomagnetic activity.’ These scanners measure the portion of the upper atmosphere, which is bombarded by energised particles, during times of high geomagnetic activity. It is only during these times that we in the UK are ever fortunate enough to witness one of nature’s most spectacular sights… weather permitting, of course.

Stunning as they may be, however, the aurorae can often be a prelude to a multitude of dangers. They are caused when plumes of strongly magnetised plasma and gases are billowed forth from the sun in what is called a ‘coronal mass ejection’. When these particles interact with the Earth’s magnetosphere, they move along the Earth’s magnetic field lines, until they reach the atmosphere, where they interact with varying gases (hydrogen, oxygen and other latent atoms), emitting light of different colours based upon the gas, which is what we see arcing across the midnight zodiac.

These same particles have to pass through thousands of satellites orbiting the Earth in the Van Allen Belt, a radiation belt surrounding the Earth which becomes highly energised during geomagnetic storms. When this belt becomes energised, ‘it can damage components in satellites, satellites important for navigations and communications.’

Professor Wild also commented that ‘as well as the potential damage to satellite circuitry, the electric currents transmitted from geomagnetic storms can also reach power grids.’ This is markedly seen in the 1989 geomagnetic storm, which overloaded a power station in Canada, leaving six million Canadians without power for nine hours! More worrying, however, is the fact that we don’t truly know how strong one of the worst storms can be.

Hence, the study of aurorae is a rather important one; knowing when the next coronal mass ejection is going to occur allows the scientists at Lancaster to be able to give advance warnings not only to the media, but also to scientific institutions, such as the British Geological Survey, and to power companies, such as Scottish Power and EDF. The UK National Risk Register of 2013 states that there’s a 5-50% probability of a ‘severe space weather’ event. However, for there to be significant long-term damage, there would have to be a storm such as that we haven’t seen since the 19th century. Thankfully, ‘the activity of the aurorae today is nothing compared to during the 18th century, where there were multiple major recorded astrological events’ … so there isn’t anything to worry about, at least for the time being.

For something so majestic, there are no words that can truly do justice the terrible, yet beautiful might of the aurorae. For something so captivating, something that awakens a deep sense of awe, aurorae can act as precursors to potentially crippling solar-storms, which could alter the very fabric of modern existence. In that sense, the aurorae are a humbling phenomenon that will stay with mankind for as long as we live on our little blue orb.

AuroraWatch UK is a service hosted by the physics department at Lancaster University, taking data from multiple SAMNET stations across the Northern Hemisphere. If you are interested in finding out about the aurorae and AuroraWatch UK, visit http://aurorawatch.lancs.ac.uk/ to find up to date activity data. You can sign up to their mailing list on the website, or through Twitter and Facebook. You can also download the AuroraWatch app, which gives live-updates on aurora activity on your phone or iPad.

Professor Jim Wild is Lancaster University’s resident aurorae expert and has regularly been to the Arctic Circle to analyse the patterns and behaviour of aurorae and geomagnetic activity. Where he hasn’t been quoted, his input and expertise helped to create this article.

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