Light Displays
- Aurora Borealis and Aurora Australis:
- This is a phenomenon of the area around the magnetic poles. As the charged particles of solar wind react with nitrogen and oxygen in the upper atmosphere, colourful flashes of light are created. The light appears to ripple over various lengths of time.
- Green Flashes:
- As the sun sets or rises, the atmosphere refracts sunlight, creating colour. Particles and water vapour in the air eliminate some of the colours, leaving green and red. The green flash lasts longest toward the Poles.
- Novaya Zemlya Effect:
- Just above the horizon, the light from the face of the sun is bent into thin slits. This is best seen at the higher latitudes, but to some extent the middle latitudes.
- Halos:
- A corona, which forms a circle around the sun or the moon, is created when light rays pass through thin clouds containing small droplets of water. If the light is diffracted, colourful circles will be produced. A halo is formed when the light is reflected off high ice crystals. When the halo is not a complete circle, it is known as a sun-dog or a moon-dog.
- Mirages:
- Temperature and light change can refract an object's location and appearance. If the ground temperature increases, an inferior mirage occurs. If it increases with height, a superior mirage occurs. A highway mirage is caused by the heating of the pavement. What appears like a pool of water is light being refracted in your line of vision. The shimmering is caused by the air movement. Fata morgana and fata bromosa are extreme mirages.
- Rainbows:
- They occur when sunlight is refracted as it enters water droplets, then is reflected off the back of the droplets, then it is refracted again. The refraction causes white light to break into the various colours. If the sunlight should bounce twice within the droplets, a larger, fainter rainbow can be seen. A rainbow will be seen only when the sun is at the back of the viewer.
- Sunbeams:
- Crepuscular rays are light and dark beams fanning out from the sun. The bright rays appear when sunlight shines between broken or scattered clouds. The darker rays are shadows of the clouds cast upon the particles in the air. Anti-crepuscular rays can be seen at 180 degrees from the sun. Light pillars are tall, bright vertical streaks of light above or below the sun just before or at sunrise or sunset.
