Written in the Sky: Aurora Borealis Explained

Uploaded by InstituteofPhysics on 01.03.2012

Dr Jim Wild: The Aurora Borealis or the Northern Lights are one of nature's most mysterious displays. In the past people thought that these lights in the night sky were the souls of the dead, ghosts sending messages down from the afterlife to people awestruck on the ground underneath.
And you can sort of see why, there is something very spooky about all of this. But in some ways the excitement is figuring out the science behind the magic. And that in itself is quite magical.
I'm Jim Wild and I am determined to unlock the secrets of the aurora. Not just because they are mysterious and magical but because they tell us something about how we are connected to what's going on in space. And that's going to become increasingly important to our way of life.
If they are not ghosts what are the Northern Lights? In this model, I've got tubes filled with argon gas and I am running an electric current through them and it is making the argon glow. In the upper atmosphere, oxygen atoms are being bombarded by electrons from space and that makes them glow. So the physics is just the same. It is amazing really but under bombardment from space the air that we breathe starts to glow.
Nobody understands how the electrons collect so much energy on their way down to make the aurora. So if I am going to figure this out I need to collect more data. I need to go and find the aurora. You don't usually find the aurora in Britain, we are too far South. Because the Earth's magnetic force field only guides particles down near the poles, to find the aurora I am going to have to head North.
One of the best places to see the aurora is Iceland so I am heading to the northern tip of a very northern country.
To run an experiment like this you need a strange combination of things. You need a dark field a long way from buildings and towns but I also need some power and some internet but luckily I've found a very helpful farmer and I can use some space on his land and so we actually get some really nice space physics in and amongst the cows.
This box is what I call my TARDIS It's full of high tech camera equipment and computers and enables me to make really good measurements of the aurora.
The camera has got a fish eye lens so I can take a picture of the night sky every few seconds. But I have got to make sure it is pointing straight up so I get a proper image of the whole sky.
Okay so that's taken a good image. We'll now try to have a display of it and see what we can see.
That seems to be working we have a sharp image, that's good. The camera works so I feel safe.
I can stitch together pictures that are taken all night and make them into movies which then show me a whole night’s activities in a few seconds, which give me a really good record of when and where the aurora appeared.
Tonight, well at the moment, I can see some really nice clear sky actually and some wispy clouds. There's a breeze blowing it by so could be good.
I am sitting here in a cold field in Iceland waiting for the Northern Lights to come out. The sky at the moment is partly clear and partly cloudy so there are some good gaps in the sky so the cloud is leaving some windows that the aurora might peak through.
Right now, I can't see a great deal. I think the cloud has come in a bit, rolled in. It is going to obscure our viewing, probably, tonight.
I don't think I am going to see anything. So I think I am going to give up, go to bed. I have got another field site so I am going to try there tomorrow, see if I can catch some aurora.
The aurora are mysterious in lots of ways. Scientists for a very long time couldn't work out where the electrons that hit the upper atmosphere come from. Strangely, this great night time show is caused by the Sun.
Electrically charged particles pour off the sun and stream past our planet. And some of the particles get trapped by the earth's magnetic field. So the stronger the wind blows, the better the aurora. So this link to the sun means the aurora are a great barometer of solar activity and what is going on in space around us.
And this really matters because giant solar eruptions that create great auroral displays also cause geomagnetic storms and these have led to problems with communication systems and navigation systems and can also wipe out power grids.
There's a risk that an electromagnetic tsunami could really interfere with our high tech society. So by studying the aurora I can understand space weather better and help us protect against storms in the future.
This is my second observatory. By having two different sites I get two different views of the night sky and it means if one site is cloudy then the other site might be clear. So it increases my chance of actually catching the aurora.
At the moment the sky is looking a little bit cloudy there is some cloud around. I need to check some other things as well ‘cause it is obviously not just down to clouds. So I have been checking out the activity in space. So images of the sun from the day before yesterday are showing that there are these active regions, these really bright regions. So they actually fired out some material so this pinged out like a catapult into space. So that's actually heading toward the earth so this material when it gets to the earth, could cause the aurora.
We've got other spacecraft. Some sentinels that sit up stream of the earth so they are getting advanced notice of everything coming our way. And they are showing that at the moment the solar wind is looking quite good for generating the aurora.
So everything is ready. Just waiting to see what nature does now.
I think that's aurora up there.
Yeah, yeah it is arriving over there, just over the horizon, so there it is. Excellent, excellent. Oh that's brilliant. Yeah. This is a really good show tonight. I am going to get some really good data I think.
I can compare those measurements to data from satellites that are flying over the aurora. Ripples in the earth's magnetic field are energising electrons and are firing them in towards the earth. It means I may have found the elusive energy source that powers the aurora.
It is really weird because I am trying to figure out what is making that light in the sky. What's making the aurora and it is not like when you figure out a magic trick it suddenly seems less impressive. Looking at the aurora, you know, it is more impressive when you figure out how it works. It is kinda more magical.
Whenever I get to see a good auroral display like this, it makes me think about the old stories that the Northern Lights are messages from another world.
And there's something in that really because the Northern Lights are telling us about our connections to space. They are bringing messages from the sun and those are messages we need to listen to.