National Geographic always presents nature with spectacular beauty. Fascinating explanations and images are always in order.
See the Northern Lights in Salten, Norway, in a time lapse manner. Not everyone is fortunate enough to see it for themselves. So use this opportunity to see it from the comfort and warmth of your internet connection.
Amazing Northern Lights Time Lapse
January 26, 2009
The Northern Lights are one of nature’s most spectacular visual phenomena, and in this time lapse video they provide a breathtaking display of light, shape, and color over the course of a single night in Norway.
Auroras, sometimes called the northern and southern (polar) lights or aurorae (singular: aurora), are natural light displays in the sky, usually observed at night, particularly in the polar regions. They typically occur in the ionosphere.Aurorae are produced by the collision of charged particles from Earth‘s magnetosphere, mostly electrons but also protons and heavier particles, with atoms and molecules of Earth’s upper atmosphere (at altitudes above 80 km (50 miles)). The particles have energies of 1 to 100 keV. They originate from the Sun and arrive at the vicinity of Earth in the relatively low-energy solar wind. When the trapped magnetic field of the solar wind is favourably oriented (principally southwards) it connects with Earth’s magnetic field, and solar particles enter the magnetosphere and are swept to the magnetotail. Further magnetic reconnection accelerates the particles towards Earth.The collisions in the atmosphere electronically excite atoms and molecules in the upper atmosphere. The excitation energy can be lost by light emission or collisions. Most aurorae are green and red emissions from atomic oxygen. Molecular nitrogen and nitrogen ions produce some low level red and very high blue/violet aurorae. The light blue and green colors are produced by ionic nitrogen and the neutral nitrogen gives off the red and purple color with the rippled edges. Different gases interacting with the upper atmosphere will produce different colors, caused by the different compounds of oxygen and nitrogen. The level of solar wind activity from the Sun can also influence the color of the aurorae.
Typically the aurora appears either as a diffuse glow or as “curtains” that approximately extend in the east-west direction. At some times, they form “quiet arcs”; at others (“active aurora”), they evolve and change constantly. Each curtain consists of many parallel rays, each lined up with the local direction of the magnetic field lines, suggesting that aurora is shaped by Earth’s magnetic field. Indeed, satellites show electrons to be guided by magnetic field lines, spiraling around them while moving towards Earth.