Low budget auroras in TromsøThe aurora* is the most impressive sight of our skies, with the only rival of total solar eclipses. They are the result of the interaction between charged particles coming from the Sun and our atmosphere. Instead of trying to explain this with my own, boring words, I recommend this wonderful video from the University of Oslo.
*Known as aurora borealis in the northern hemisphere and aurora australis in the southern hemisphere.
 Auroras in a terrella
This explanation was first introduced by Kristian Birkeland, who reproduced auroras in his lab using a magnetized sphere called terrella.
 Video of auroras from the ISS.
You may have noticed that auroras come in colours. This is because the charged particles can interact with our atmosphere at different heights, mainly with oxygen (red/green) and nitrogen (red/blue). Different combinations also result in yellow or pink auroras, but green is by far the most common. You can read more about this in the Wikipedia article.
It is also worth noting that auroras are not exclusive to Earth. As terrellas demonstrate, they will occur in any sphere with an atmosphere and a magnetic field which encounters charged ions. However, we may need to look in ultraviolet (like in the examples below) or other light frequencies to find them.
So now you have an idea of what auroras are. What about going to see some?
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Arriving at Oslo, from a train window.
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Auroras happen almost everynight somewhere around the world. But that doesn't mean catching one will be easy. As you could learn in the video, auroras are mostly seen at high lattitudes and, for obvious reasons, you want to see them at night. If you live in America you may try going to Alaska (perhaps Canada). In Europe there are several spots, from Rusia to Iceland. I can recomend Tromsø.
For a long time I had wanted to see auroras. I guess it was kind of a dream I did not think much about, because I did not consider I had any real chances in the near future. Then my uncle went to work in Oslo for a time, and I knew a visit could be my perfect opportunity.
Tromsø is the biggest city in northern Norway, well over the Artic Circle. It is a particulary convenient spot because the Gulf current makes it unusually warm for its lattitude. There are dayly flights from Oslo and many from other cities in Europe, so getting there is not so difficult either. The biggest drawback is Norway itself: so expensive! 
This is in part the reason why we—my now wife and I—dicided to organize a lightning visit, with only two nights to see the auroras. I was about to mention that we arrived “at night”, but being over the Artic Circle in January, that goes without saying. Anyway, the weather was terrible. It was covered with clouds and snowing. It did not look too bright for the auroras.
 You'd think it would be empty
Tromsø was actually more beautiful than I had anticipated, unfortunately, we bearly had time to explore it. The scenery with the steep hills that end in the sea is amazing, as you can already see from the airplane.
 Looking tough with Amundsen
During the day hours there was a long twilight, but never proper day. Because it was snowing, we entered into a random museum—which was nice, by the way. There are many things you can do in Tromsø, from snowmobiles to hiking and museums. If you have the money and time, it is worth it.
If you want the best chances to see the auroras, there are many agencies specialized in taking you to the right spot at the right time, far from clouds and the city lights. You can also book interesting plans like auroras and sled dogs, auroras and snowmobiles… you name it. But, of course, all those excursions come at a price. Remember we are talking Norway here. Another option (not much cheaper, of course) is to rent a car and try on your own. Needless to say, it can be dark and cold, so be responsible.
 Snow-wigs
The second and last night arrived and we had little hope of success; the sky was still cloudy and there was no sign of auroral activity. Nonetheless we took a stroll around Tromsø to test our luck—we could not afford a fancy aurora excursion, specially not given our grim chances of success. We found a nice cemetery a bit secluded from the city lights, but the sky was thick with clouds, so we got back to the hotel.
 Night dragon
But we did not give up. We went out for a second walk and progressively some clearings appeared amongst the clouds. At first there were no auroras in the dark sky. Suddenly, we spotted something, however so dim. Little by little the aurora brightened to reveal its true nature. What a sight! Narrow auroras like green dragons crossed the sky from horizon to horizon. And they kept growing. After a while pink auroras joined the green; it was truly awe-inspiring.
We did not have the right gear to take the pictures; we didn't even have a tripod! Only because the auroras were so bright we could take some decent pictures. In most of the pictures below the exposure time was set to 2.5s. In some cases I used Ana's head as a tripod, but you can understand why some look a bit blurred.
Sorry about the nasty compression artefacts. It is not easy to solve this problem with Weebly and dark pictures. But they are good enough to get the idea!
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The aurora is really one of the finest views on Earth. You have to see for yourself how peacefully it dances in the sky; it is almost an spiritual experience—and really, how could the men of old times think of the aurora as anything but the spirits of the Wild?
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