The sun isn’t a tidy sphere. If you go a little closer, you’ll see it looks a bit… fuzzy. Its plasma doesn’t sit as a smooth surface; it’s a roiling sea, throwing itself high above the sun, responding to magnetic fields that would tower many times over our entire planet in a way that would make any sane person feel very tiny indeed. So best not to think about the scale of it too much. We get enough existential panic from the possibility of a Michael Bay remake of Teenage Mutant Ninja Turtles.
Some of this plasma gets enough of a kick to leave the pull of the Sun altogether, and it heads out into the universe. It’s barely there – just some electrons and protons held together by the merest hint of a magnetic field. But it’s there. After about 18 hours, if it’s lucky, it’ll hit the Earth. Now, it might have whizzed passed Mercury and Venus, but the Earth is slightly different – we have a magnetosphere.
Our magnetosphere is the area around our planet that is affected by our magnetic field – the same magnetic field that makes compasses point north. When the plasma hits our magnetosphere it gets pulled around us, following our magnetic field lines right to the poles.
We’re almost at Aurora. The next thing you need to picture is an atom. The classic orbital model is probably what you’re thinking of here, and that’s the most useful way of picturing an atom when we’re talking about Aurora. The reality of life inside an atom is very different to the image of electrons whizzing around the nucleus in a neat orbit – electrons are closer to clouds of probability, and, well, the whole thing is a mind-bending hot mess. But the orbital model is a useful way to think about certain properties of the atom, without all the quantum weirdness, so let’s do that.
So in this model of the atom you can have electrons whizzing around the nucleus in different orbits, at different distances from the centre. It’s possible for an electron to jump up to a higher orbit if it gets a jolt of energy from somewhere.
And that’s what this plasma from the Sun does – as it hits our atmosphere it gives the electrons in the air a boost into a higher orbit (or energy level, in the parlance). But the atom has rules. It has rules! They shall not be disobeyed. And one of the rules says that the orbits around the nucleus have to be filled from the lowest to the highest, with no gaps in between. So if an electron jumps to a higher orbit, that means there’s a gap underneath it. So it has to drop back down. But it’s gotten this energy from the plasma, and it has to do something with that energy – it can’t just ignore it or give it back. So this electron gives off a photon of light, which allows it to drop back down where it came from.
And when this process happens a lot, all at once, you get the Aurora. So the poles would be a good place to study them – however, the poles are a strange place, full of strange people, and who knows what could happen…
Incidentally, you can find out more about the Halley Research Station (where our heroes are stationed) here.