Class Notes: 2b – The Northern Lights
The Northern Lights (which are also called the ‘Aurora Borealis’ are one of the most amazing natural light shows that you’ll see – well at least on Planet Earth!
The scientific explanation behind the Aurora Borealis is almost as improbable and magical as the lights themselves. The Earth, it turns out, is constantly bombarded by highly charged particles blown around by solar winds. Few of these particles ever reach the atmosphere because they are deflected by the Earth’s magnetic field.
But every so often, the gentle solar winds turn into geomagnetic storms. Solar flares and coronal mass ejections – explosions of solar material into interplanetary space – can send powerful waves of charged particles toward the Earth. When these cosmic electrons collide with the Earth’s magnetic field, they generate millions of amps of electric current that arc along the magnetic field toward the poles.
If the force of a geomagnetic storm is severe enough, particles will breach the magnetic field at the poles, creating what is essentially the world’s biggest neon sign. As the supercharged electrons pass through the atmosphere, they excite gas atoms like oxygen and nitrogen.
The excited gasses emit different coloured lights depending on their altitude and the power of the surge. Low-altitude oxygen is responsible for the fluorescent green hues and high-altitude oxygen produces those brilliant crimson reds. Nitrogen flares up as shades of blue and purple.
The Aurora Borealis are visible around the North and South Poles.