The Aurora lights – known as Aurora Borealis in the northern hemisphere and Aurora Australis in the southern hemisphere – are one of the most beautiful natural phenomena the planet has to offer. Thousands of people flock to see the Borealis each year, to get an eyeful of the dancing curtains of light that have transfixed humans for thousands of years. However, very few people know exactly how the lights are caused – seeing them simply for the ethereal beauty that they present. The workings of the Aurora, though, are just as fascinating as the Aurora themselves, and add to the beauty and grandeur that the lights possess.
A solar windy day
As with a lot of the good stuff about our planet, we have the sun to thank in part. The sun frequently releases streams of highly charged particles that are known as solar winds. Being launched from the sun, these solar winds are extremely potent, carrying immense amounts of energy and traveling at extreme speeds. Not long after being released, solar winds reach supersonic speeds, and can continue unimpeded far into the solar system, only ceasing to be supersonic when they reach a distance almost more than twice that which lies between the sun and the planet Neptune. When these solar winds interact with a planet they can, over time, strip away its atmosphere, and scour the surface of the planet with radiation.
Magnetic field day
With all that said, you might be a little worried about the presence of solar winds. After all, traveling as far as they do, we must be bombarded with them all the time which, given what we now know, doesn’t sound like a particularly appealing prospect. Well, we are indeed bombarded with solar winds on a fairly regular basis – but as you might have noticed, the Earth isn’t currently a barren, irradiated wasteland. For that, we have our magnetic field to thank. The liquid iron at the Earth’s core creates a magnetic field through its movement, one that reaches past our atmosphere and shields us from solar winds. When solar winds hit the field, they are redirected away instead of being allowed to reach our atmosphere.
A nice atmosphere
However, the magnetic field does not drive away the solar wind without itself being affected. The magnetic field creates a magnetosphere around the Earth, which contains charged particles that are manipulated by the field. At times, solar winds are capable of altering the trajectory and behavior of particles in the magnetosphere, and carry them down into our atmosphere along with remnants of the solar wind. When these charged particles hit our atmosphere, they transfer energy to the gas particles – oxygen and nitrogen mostly – that comprise our atmosphere. When these particles calm down, they release photons – light particles. It is these light particles that make up the Aurora lights, as they shift and dissipate in the Earth’s atmosphere.
Color me excited
The color of an aurora is dependent on the altitude at which the particles are excited. At the highest levels of the atmosphere, oxygen atoms emit red light – but the concentration of oxygen is lower and our eyes are less sensitive to red light, so we don’t see red aurora very often. The famous green light of the Auroras is created by collisions at lower altitudes. The higher concentration of oxygen leads to more frequent collisions that release green light – to which our eyes are much more sensitive, making green auroras the most commonly seen.
So there you have it – the Auroras are caused by a bombardment of solar winds that would prove disastrous for us all were it not for our trusty magnetic field. If you love the Aurora lights, give thanks to the Earth for its molten core, and the sun for, uhhhhh, flinging solar winds at us constantly.