The Magnetosphere and the Aurora

Aurora australis superimposed on the blue marble. Image courtesy: NASA

It is because we have a magnetosphere that our planet has the spectacular aurora borealis and australis - the northern and southern lights that can often be seen at night near the arctic and antarctic circles. The aurora are caused by electrons from the magnetosphere being accelerated along the Earth's magnetic field into the upper atmosphere, where they collide with atmospheric particles at altitudes between 100 and 200km. The brightest colour of aurora, green is caused by electrons hitting oxygen atoms in the atmosphere.

Images from space have shown us that the aurora form ovals centred around Earth's magnetic poles. The radius of these ovals get larger and the aurora move to lower latitudes when the Earth's magnetosphere is strongly affected by the solar wind or engulfed by a coronal mass ejection, a massive explosion of solar plasma and magnetic field that travels through the solar system, often at speeds much faster than the normal solar wind. 

During the strongest events the auroral oval can reach as far south as the UK. Sign up to aurorawatch to receive alerts when you can see the aurora in the UK!

The Aurora from TSO Photography on Vimeo.

Page last modified on 16 mar 18 16:01