December 3, 2021

I, Science

The science magazine of Imperial College

This article is taken from the Winter 2011 issue of I, Science.

Richard Millar explains why the Aurora Borealis isn’t just a light-show.

Throughout human history the Aurora Borealis has been an ever-mystical backdrop and inspiration to the life beneath. Whether you see the aurora as lights carried by Norse Valkyries as they ride across the sky, or spy the swirling shapes of cities and other worlds as in Philip Pullman’s His Dark Materials, the Northern Lights never fail to cause us wonder. In today’s age of earth-orbit exploration we have unprecedented vantage points into our earthly aurora, as the awe-inspiring International Space Station time-lapse videos show. So, what is the cause of these ‘leaping heavens’ in the sky? What are the Northern Lights?

Despite the huge vacuum of space between the Earth and Sun, these two bodies are far more connected than people think. Solar particles from the Sun known as the solar wind continually bombard Earth’s atmosphere at very high speeds. Upon arrival these particles crash into the ionosphere, emitting characteristic wavelengths of light which then reaches us at the Earth’s surface. For example the characteristic green colour of the aurora comes from solar particles exciting the atomic oxygen.

So what can these celestial light-shows do for us? Will they forever remain mere natural pyrotechnics in the sky, or can they have a more direct impact on our lives? The intense electric and magnetic fields associated with auroral activity can damage electronics orbiting Earth, particularly hazardous for satellites. The next time a large sunspot is formed it could cause your TV to black out or allow your sat-nav to lead you off course!

Perhaps the most significant problem posed by the aurora is the danger to manned spaceflight. In 1989, during a particularly significant auroral storm, the cosmonauts aboard the Mir space station were exposed to more than their safe dose of radiation for the entire year. In order to effectively safeguard an ever more technologically dependent Earth, and a civilisation reaching out from our home planet for the first time, auroral weather forecasting will have to become as accurate and commonplace as today’s large-scale weather forecasts.

However, the aurora offers us advantages too. Occasionally, strong auroral currents and fields can be experienced on the Earth’s surface, affecting communication systems such as telephone networks. Sometimes the telephone lines can be arranged so as to produce geomagnetically induced current from the aurora. For instance, during one of the most violent auroral storms in recorded history in 1859, two telegraph operators 2.5 thousand miles apart were able to switch off their power supplies and communicate for over two hours due to the current induced by the aurora alone!

Nature has the power to awe and enthrall; never truer than with the Northern Lights. In order to continue expanding our domain in the universe and satisfy our unquenched thirst to further explore, the aurora must go from being something we merely marvel at to being something that we can understand and predict in great detail. In many ways, understanding the aurora really is humanity’s gateway to other worlds.

Earth | Time Lapse View from Space, Fly Over | NASA, ISS from Michael König on Vimeo