It is easier to see the northern lights (aurora borealis) in the UK than you might think. All you need is a dark place, a clear sky and very good timing!
The good timing is important as the northern lights are a result of a geomagnetic storm. These storms are short-lived periods of high geomagnetic activity where the Earth's magnetic field changes very quickly and strong electric currents flow high in the atmosphere.
The aurora is a consequence of activity on the surface of the Sun. Occasionally there are large explosions on the Sun, and huge amounts of charged particles are thrown out into space. These particles sometimes travel towards Earth where they are captured by the Earth's 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. These charged particles collide with gas molecules in the atmosphere. The energy released in these collisions is given off as light.
When a charged particle collides with a molecule in the atmosphere the molecule becomes excited. The excited molecule is unstable and will give up its extra energy by emitting light.
The colour of the light depends on the molecules being excited. Like a sodium street light which gives off an orange light, the oxygen, nitrogen and other gases in the atmosphere have their own particular colours resulting in the range of blues, greens, yellows and reds observed in the aurora.
The auroral ovals represent the places on Earth where aurora occur most often and with greatest intensity. Under normal conditions the northern oval covers 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.
On average you might expect to see aurora in the far north of Scotland every few months, but less often as you travel further south.
Geomagnetic storms follow the 11-year solar cycle. The next solar maximum is due 2013 and the chance of big magnetic storms will be greatest around then and shortly afterwards.
Generally, there are more magnetic storms around the equinoxes (March-April, September-October).
1. Look out for a geomagnetic storm
Check the internet to look for strong geomagnetic storm activity.
There are many ways to represent geomagnetic activity. One of these is the Kp index which ranks the variations in geomagnetic activity from 0 to 9, in 3-hour intervals. The larger the Kp index is, the stronger the storm and the further south the northern lights will be visible. The map on the right shows roughly where you might expect to see aurora based on Kp index levels.
Follow us on Twitter:
@BGSauroraAlerts for occasional aurora alerts
2. When there is a storm...