Mystical lights in the sky: Norway
The evening's Northern Lights show had begun.
Here in Norway, near the rooftop of the world, the sun is an elusive host from November through January. The aurora borealis is the ethereal substitute sent to dazzle in its absence.
In winter, you can best see the lights from Arctic regions like Alaska, Iceland, Greenland and Norway, usually between 8 p.m. and midnight. But they do not wait for their audience. You have to chase them.
An aurora is a natural light display in the sky, particularly in both polar regions, caused by the collision of charged particles directed by the Earth’s magnetic field. An aurora is usually observed at night and typically occurs in the ionosphere.
It is also referred to as a polar aurora or, collectively, as polar lights. These phenomena are commonly visible between 60 and 72 degrees north and south latitudes, which place them in a ring just within the Arctic and Antarctic polar circles. Auroras do occur deeper inside the polar regions, but these are infrequent and often invisible to the naked eye.
Its southern counterpart, the aurora australis (or the southern lights), has similar properties, but is only visible from high southern latitudes in Antarctica, South America, or Australasia. Australis is the Latin word for “of the South”.
Auroras can be spotted throughout the world and on other planets. They are most visible closer to the poles due to the longer periods of darkness and the magnetic field.
Auroras result from emissions of photons in the Earth’s upper atmosphere, above 80 km (50 miles), from ionized nitrogen atoms regaining an electron, and oxygen and nitrogen atoms returning from an excited state to ground state. They are ionized or excited by the collision of solar wind particles being funneled down and accelerated along the Earth’s magnetic field lines; excitation energy is lost by the emission of a photon of light, or by collision with another atom or molecule:
Green or brownish-red, depending on the amount of energy absorbed.
Blue or red. Blue if the atom regains an electron after it has been ionized. Red if returning to ground state from an excited state.