The Northern Lights, known as Aurora Borealis, are natural light displays that happen in the sky above the Magnetic pole of the Northern hemisphere.
The lights are only visible to the naked eye at night, and can be seen most clearly in areas of the North that do not have light pollution such as remote areas of Northwestern Canada and Alaska, Northern Norway, Southern Greenland and Southern Iceland.
The lights are one of the natural wonders of the world. Each appearance of the lights is unique, but most often people describe the sky as being illuminated with a band of three luminous green arcs with a touch of pink along the edge. At other times the lights appear as patches of scattered cloud, rolling smoke or as a rippling curtains effect, and the lights aren’t always green, sometimes blue or red lights will be visible.
The different colors occur depending on the altitude and type of gas emission. Oxygen emissions located about 60miles (100km) above the earth cause the sky to glow green. Oxygen emissions higher up, of heights above 150 miles (240km) from earth cause rare all-red lights whilst nitrogen emissions below 60miles (100km) high cause blue lights in the sky.
The Northern Lights happen when electrically charged particles and gas particles collide, the collisions emit light and that light is shown to us as the Northern Lights.
It all starts with the sun. During large solar explosions and flares large quantities of charged particles (electrons and protons) are thrown out from the sun’s atmosphere into deep space some of which are carried towards earth on the ‘solar wind’
When the particles meet the Earth’s magnetic shield they are mostly deflected but some are led towards a circle around the magnetic North Pole where the magnetic field is weaker. Here they enter into and interact with the upper layer of the earth’s atmosphere, colliding together.
The Northern Lights are at their most frequent in late autumn and winter/early spring, between the autumn equinox and spring equinox, and most intense during the phase of the solar cycle (which cycles over eleven years) when coronal mass ejections increase the solar wind intensity.
If you’re interested in knowing when and where the Northern Lights will be most visible next, you can check on the Aurora Forecast website at http://www.gi.alaska.edu/AuroraForecast
Sources:
Wikipedia Astronomy
Norway Northern Lights
Alaska Northern Lights
