It's a bit embarassing but I never realised who was on the 200 Norwegian Kroner note. Maybe It's because I keep them all safely locked up in my wallet. Anyway, today we had a visit from Pål Brekke one of Norway leading experts on the Northern lights. The lecture was very well presented with lots of visuals, you can get some idea from his website. So, the guy on the note is Kristian Birkeland who was the first to realise that the Aurora Borealis is due to particles from the Sun trapped in the Earth's magnetic field. The little diagram on the left is the apparatus he used to demonstrate the effect. I've been teaching students about the aurora for the past 35 years and was wondering if what I've been teaching all these years is still considered to be true. Well most of it is. The only thing that was news to me was the way the magnetic field of the earth is distorted by the field associated with the solar wind in a way that traps the particles on the far side of the Earth, see the video below at 3.30. Still not sure how to explain the magnetic field that travels along with the solar wind.