One of the most famous phenomena of the natural world, the Aurora Borealis is a stunning visual display caused by the passage of solar wind through the atmosphere. The high energy particles leaving the sun excite molecules of air and create stunning displays of color: faint, watery tendrils of blue, green, red and purple that can appear in any number of forms, from small ribbon shaped patches to vast stream-like expanses that stretch across the night sky.
The visibility of the Northern lights is dependent on location, conditions, and the activity of the sun.
Location
Living in Northern Canada, Alaska, or Northern Europe is the most convenient way to see the Northern Lights. If there is a solar storm, and a great deal of electrified matter leaves the sun, it is possible to see the lights from closer to the equator, but still rather unlikely. A similar phenomenon may be observed in the Southern reaches of the globe, called the Aurora Australis, but it is less famous.
Conditions
Even if you happen to be located close to one of the magnetic poles, a number of factors can play into the appearance of the lights. The angular polarity of the Earth's magnetic field relative to the solar wind plays a major role in the visibility of the lights and the intensity of the lights, due to the interplay between the Earth's magnetic field and the solar radiation the most visually stunning displays are only seen when the magnetic field is out of alignment.
Good weather is also key. Cloud coverage can obstruct visibility of the Northern Lights, as the reactions that generate the light take place far above the cloud layer in the outer reaches of the atmosphere.
Conditions on the ground can affect the ability of a viewer to perceive and appreciate the lights. Light pollution from vehicular traffic, residential buildings, and other viewers can diminish the appearance of the skies, and vegetation may obstruct your view.
Solar Activity
As I have alluded in earlier portions of this piece, the primary event that triggers the Aurora is a solar emission. This is a poorly understood (by me) event wherein the sun releases an above-average amount of high energy particles into the solar system, some of which eventually stream over to the planet Earth. This is a variable process, and quite unpredictable to the average observer, but the National Oceanic and Atmospheric Administration publishes an index to help people predict the degree of activity that we can expect from the Aurora lights every three days.
If you have the opportunity, you should take advantage of the chance to see the northern lights billow across the heavens.
