I've always wanted to see the northern lights in person, but in the meantime I experimented with capturing time-lapse video from web-cams set up on the Nature of Jokkmokk site.
While being careful not to overload the site, I set up a job to download images from one of the site's webcams every 5 minutes over a 5 day period, and found that the northern lights lit up the night of the 23rd/24th January 2013. It was then fairly simple to stitch the images from this night together using ffmpeg and some advice in Paul Rouget's blog post.
Once the pictures are downloaded to a directory and named file_1.jpeg, file_2.jpeg, ... in chronological order, ffmpeg can be run to stitch the pictures together into video in formats supported by browsers (.webm,.mp4 and .ogv). I used the following ffmpeg switches (using -b 1000k to try to include reasonable quality allowing a 1M/second bitrate).
ffmpeg -f image2 -r 10 -i file_%d.jpeg -vcodec libx264 -b 1000k out.mp4 ffmpeg -f image2 -r 10 -i file_%d.jpeg -vcodec libvpx -acodec libvorbis -b 1000k out.webm ffmpeg -f image2 -r 10 -i file_%d.jpeg -acodec libvorbis -b 1000k out.ogg
If your browser supports HTML5 video and any of the above formats, you should be able to view the short clip below
For some brilliant still picture highlights captured over many years, see the Nature of Jokkmokk Best Shot Album. The location of the webcam is displayed in the following open street map: