If someone asked an image to define Halley, it would be without doubt, a photo of the modules with an magnificent aurora on the background. That on is actually one of the most known and divulged photos of the station, that got taken by several people on several occasions during the several years that Halley has been in Antarctica.
The continent is awesome to watch these phenomena since it is enough South to be able to spot auroras in pretty much all its extension (we were just shy of 50 kilometers from the coast and we got some of the most vivid and intense auroras in the world) and few people means less light and atmospheric pollution, which is great to watch pretty lights in the sky.
But even though it is such a famous and publicized phenomenon, only an handful of people each year have the opportunity to watch auroras in Halley. The reason is simple. During Summer, even as late as early March, when captains are playing Titanic a bit by keeping a ship around Halley so late in the season, there is still too much light around to see anything good. For reference, my first and last auroras were the greatest ones. Between those we had a few more but none with the intensity and color variety like these.
The first one came out in early April, when our days were still half and half regarding the day-night cycle, and the last one was right on the first week of August, just two weeks shy of the first sun up after Winter.
What’s an aurora after all? The correct scientific explanation is too complicated and takes too long to expose, but in its essence is boils down to this: the Sun is constantly spewing particles smaller than an atom is all directions. These particles are protons and electrons that are ejected from the Sun at very high speeds. Since our planet spins happily around it, every once in a while it gets in the way of the odd jet of these particles right into the atmosphere. Fortunately for us our planet has a built in shield. Its the magnetic field and since all these particles spewed by the sun have electrical charge, these are diverted from the fragile humans and all the rest of the terrestrial life that goes on bellow once they get into its action radius. And luck for us too because if it wasn’t for Earth’s magnetic field, the atmosphere had no other option but absorb the energy from these particles and let a lot more go through to the surface, which would make life on Earth quite complicated since we tend to like warm temperatures and not having high speed protons and electrons jammed into our foreheads all the time, something that tends to cause cancer and other skin problems by the way.
But this shield is not perfect. Sometimes, when the Sun is in a fouler mood and it is vomiting electrons and protons over to us like he just had drunk a milkshake with that milk carton that went the whole Summer open in a cabinet, the magnetic field gets a bit shaky and some of the faster particles can go through to the upper atmosphere.
Now, these ones go around very fast and when they get to an area full of slow moving atoms and molecules, like pretty much most of out atmosphere, its a matter of time until something crashes around. Its just like someone exiting a motorway at 120 km/h straight into an underground shopping mall parking lot during rush hour. Sooner or later he’s going to be without an airbag.
For this particles, the airbag bursting is the light that we see high in the sky.
As I said before, these particles have electrical charge and are smaller than atoms. When they get close enough to the atmosphere atoms and molecules, they get trapped by their electrical field. The electrons are specially keen to it.
But if they are cruising the space at full speed and then they got trapped, doesn’t that creates problems? What happens to its energy and speed?
Well, first of all, in science (and physics in particular), speed and energy are pretty much the same thing when we look at something that small. Just like light, which is nothing more than energy being transfered as radiation. And there’s where the trick is: when these particles can bypass Earth’s magnetic field and are captured by others, all the energy they have (most as kinetic energy) is released as light…normally green, red, sometimes yellow and, with some luck, even violet sometimes.
This is all nice and pretty but in the end of the day its lights in the sky, that is, you can only see them if its dark and that’s why this show is winterers only.
But even during Winter, including the 107 days without Sun even, auroras don’t happen every odd day and after dinner for good measure. Its hard to give a correct number for how many auroras that I’ve seen during last Winter since some had already gone by the time I got enough clothes on me to go out into the -30 ºC snow taking pictures. There were just two occasions were the show left us with our jaws hanging open wide. Other than that, once in a while we got a smoker coming back inside yelling that the sky was green again but when the rest was able to get out there, it was usually a disappointment. That’s what happens when your first aurora ever is one of the biggest ones around – we became aurora spoiled.
In order to see a proper aurora in Halley we need 3 fundamental things:
1 – An aurora in the sky (Duh…)
2 – Just enough darkness to be able to spot it.
3 – A cloudless (or close to it) sky.
The third one was always the tough one to get. We could be staring straight into the most violent and bright aurora ever but if we have a thick layer of low level clouds hanging at 300 meters high, which is sooooo Halley, we are not going to see anything, not even a flash just to tease us with what’s going on behind the blanket.
In Halley auroras were always detectable by the two engineers. My counterpart had a project to detect low frequency radiation waves . Whenever we had an aurora on the day before (and it was too cloudy to see it), the data from this experiment always showed several absorption spikes from radiation gotten from the aurora.
Myself on the other hand was able to detect them through the infrared camera footage. From all the light emitted by an aurora, only a part is visible, that is, is able to be seen by human eyes as green and yellow waves in the sky, but auroras also emit in the infrared and ultraviolet radiation spectrum and I had a camera to detect the first one. Clouds are still visible, even when looking only in the infrared part of the spectrum. But if there’s an aurora behind them, the video looks like there’s a thunderstorm between the clouds, with light flashes popping out from between the layers.
Its not the same as a live one of course, mainly because infrared images go in several shades of gray, but at least I made sure that I had slept under an aurora on the night before.