The wonderful aurora borealis
When Tanya and I decided we would go to Norway, our primary motivation was to see the aurora borealis, the famous and elusive northern lights. We knew that there was no guarantee of seeing them; that you have to have the right latitude, a dark location to watch from, and the right weather conditions, both terrestrial and solar. The first two conditions are easy to sort out - we went to Tromsø which is at 69 degrees north, and we rented a cabin in Svensby, far from the city lights. We chose to go when the moon had waned to its minimum. The weather, well that was the trick, and there was nothing we could do except to go and hope for the best.
There are some useful internet sites that can help you work out the likelihood of seeing the lights. They generally show something called the Kp index. The higher the Kp index, the further south it might be possible to see the lights. A Kp index of 2 or higher means there's the chance of lights overhead in Tromsø. The 27 day solar weather forecast from NOAA gives the forecast Kp index for a given day out to 27 days in advance. Spaceweather's auroral oval page shows short-term forecasts of likelyhood of visible aurora, plus near-realtime satellite data showing current auroral activity. For "is it happening right now?" type questions, the best site I found was Tromsø live. There you'll find a live Tromsø all-sky camera, and live magnetometer readings.
These sites are all well and good but to use them you need internet access, which we didn’t have at the cabin in Svensby. For our aurora searching we were back to the good old “head out and see what you see” technique. It turned out well for us.
The lights generally appear between 18.00 and 24.00 local time, so from 18.00 onwards on our first night in Svensby we started checking the sky every ten minutes or so, looking out of a small north facing window. At 18.00 there was still quite a glow from the sun on the horizon, and it wasn’t until later (about 19.30) that the sky was properly dark. We could see the stars beautifully, and then at one point a definite glow across the northern horizon. Could it be the lights? We raced out of the cabin and into the snow, and sure enough it was!
Tanya in front of the aurora borealis right after we first saw it.
A band of light was stretching across the horizon from south-east to north-west. It was very beautiful, and constantly changing, but so slowly that you couldn’t notice the changes as they happened. It was getting gradually stronger. We marvelled at this sight for quite a while, getting cold in the snow, and we decided that the lights from the cabin were too strong and that we should move. We jumped into the car and headed north.
After driving for a while we found a good spot with no house lights and jumped out of the car, and it was then that the show really started. Tanya was first to notice the lights rippling. Whereas before the lights had been a band of light green in the sky, they were now a strong green colour, with occasional red fringes, forming in curtains across the entire sky. They were moving faster and constantly changing, coming and going, forming spirals and whiskers and bands of colour. We both saw the next ripple because it was impossible to miss. The lights got brighter and brighter, and then started moving incredibly fast, shooting out arms of light that formed into off-shoots of colours, purples and reds and whites amongst the background green. The speed of movement was phenomenal; the lights would shoot across the entire sky, horizon to horizon, directly above us, and so brightly that the snow was lit up green.
These two pictures were taken within a minute of each other.
We did not know where to look. I was trying to take photographs but for the most spectacular segment I was too awestruck to look down at the camera. Tanya and I were literally breathless, incoherent with excitement and trying to point out all the different patterns that were appearing, disappearing, rippling and dancing in the sky.
The aurora and a passing plane, over a 30 second exposure.
The lights were present in the sky, ever changing, for at least five hours that night, and for many hours the night after as well. Both nights we drove around in the car, stopping at various places, each time seeing the lights from a different angle and watching them. They seemed to form in bands which shifted slowly, with occasional flare-ups that were the most spectacular parts. At some point curtains of red and purple formed and disappeared quickly on the horizon, and at other points the entire sky was covered in green. The aurora borealis is one of the most beautiful and magical things I have ever seen. It is a true wonder of a constantly surprising world, and I won’t forget it.