This image was created in Photoshop CS5. We are too far South here in Rotherham to see the Aurora. So I thought - why not have a go at creating one of my own. This is the result. I used screensaver pattern and a combination of radial and gaussian blur filters to produce the aurora. I used a mask with a selection and refined edge to drop the aurora in as a sky replacement. I then used a combination of levels and hue and saturation to darken the image. Then in Camera Raw I adjusted the fill light and recovery sliders to bring out the sky. Finally, used the blur tool on a separate layer to blend the strands of the aurora into the sky and added a few stars.