One advantage of living in Northern BC is that you don't have to travel far from bed to see the Northern Lights.
Aurora Borealis or Northern Lights over the Crooked River . The shot is a long exposure on a particularly dark night and I was happy to capture my first high altitude blue/purple aurora. The blue/purple fringe on the top comes from the interaction of the solar wind with hydrogen and helium in the ionosphere. Below that is the band of red or blood aurora that forms around 250 – 500 km from high energy state excited oxygen atoms emitting light at 630 nm. The bottom layer is the more typically seen green aurora that forms between 100 – 250 km by excited oxygen atoms emitting light at 557.7 nano-metres. The green band in this shot here actually has a yellowish tinge as we are looking at the auroral oval from a long way away. This happens due to the shallow angle of observation causing the green and red bands to overlap generating a dirty green or yellow rather than the vivid green you see with overhead auroras. At the lower edge of the curtain (below 100km), the density of molecules doesn't permit oxygen to emit light. It is however possible to see a low altitude fringe of blue or red below the green oxygen layer that comes from Nitrogen atoms either in its ionised or excited states respectively. This is not present in this photo and is typically only seen at very high latitudes when standing under a powerful overhead aurora. The Crooked River sits at 54 degrees North in Northern British Columbia.
