Aurora borealis

In the Burren for the weekend. May is the best time of year for the flowers in the Burren limestone scenery, in particular I like the gentians and mountain avens. But today was remarkable for an amazing auroral display after it got dark.  At first I though it was just high cloud, a white streak high overhead, and I expected an auroral display  to be to the north, but the cloud was a funny shape, streaky with long filaments. More did develop to the north later and today's blip is the north west horizon, with the new moon low down.  The extra is the overhead formation that was more prominent early on.

An auroral display works on the same principle as a neon light, with the electric current produced by charged particles coming from the Sun. The particle are funnelled in to the magnetic poles. The current excites electrons in oxygen atoms in the atmosphere and these electrons then only lose their excess energy when the oxygen atoms collide with each other. At ordinary atmospheric pressure the atoms collide so frequently that  they don't stay excited long enough to produce an effect. But if the pressure is low enough the atoms collide less frequently and can stay excited for longer, but will eventually lose their energy and emit light with these beautiful green and red colours.

The photographs are much more spectacular than what you see with the naked eye, the colours were very vague, almost white, to the naked eye, but the camera sensor is much more sensitive to red and green than the human eye. I didn't have a tripod, so the camera was just hand held.