Last week much of the UK witnessed the spectacular displays of the Northern Lights, but what causes this phenomenal natural light show? Here’s your quick fire science on the aurora borealis.
- The northern lights appear when electrically charged particles travelling from the sun, known as the solar wind, disrupt the Earth’s magnetic field and collide with oxygen and nitrogen atoms in the atmosphere.
- Having collided with the charged solar particles, the gas atoms get excited and release energy, which makes them glow.
- The different colours seen in the displays are determined by which atoms are hit and how much energy they have absorbed
- Oxygen atoms release red light at high altitudes and green light at lower altitudes. Because of the higher air pressure and relatively high amount of oxygen at lower altitudes, green auroras are the most commonly seen.
- Because the flow of charged particles coming from the sun is directed by the Earth’s magnetic field, displays are mostly seen in the Polar Regions.
- At the North Pole this is known as the aurora borealis, but at the South Pole the event is called the aurora australis.
- While particles can strike the atmosphere at any time, the northern lights are usually seen at night because they are not a bright as daylight.
- Auroras have been observed on many other planets like Jupiter and Saturn and even on the surface of Jupiter’s moons.
- There are many myths surrounding the auroras, in medieval times they were thought to be a sign of oncoming war or famine.
- Occasionally there are huge explosions on the sun known as solar flares which throw off huge amounts of charged particles. If these hit the Earth they can distort the magnetic field and produce aurorae much further south
- The sun is currently at the height of its 11 year solar cycle when these flares are most common. A particularly large burst of solar wind last week led to the northern lights being visible all across the UK, even as far south as Jersey.