The northern lights, also known as the aurora, are a dramatic, colorful, and magical display of light seen above the magnetic poles. They are called aurora borealis in the northern hemisphere and aurora australis in the southern hemisphere. The northern lights display a variety of colors the common being pale-green, pink, and purple. In some places, shades of violet, blue, green, yellow, and red have been reported. The lights are not defined and can appear in many forms ranging from scattered clouds of light, rippling curtains, patches of light, and shooting rays in the sky.
Causes of Auroras
Auroras are caused by the collision of gaseous particles in the planet’s atmosphere with charged particle released by the sun. Colors vary depending on the type of particles colliding. The most common northern light is pale yellow-green, which is caused by colliding oxygen molecules located 60 miles above the earth's surface. The purely red aurora is the rarest and it is caused by high altitude oxygen located 200 miles above the surface. Nitrogen causes the blue or purplish-red lights.
In the 1950s, researchers realized that protons and electrons from the sun were blown towards the earth by solar winds. The sun’s high temperature causes frequent and explosive collision between gas molecules. As the sun rotates, the free protons and electrons are thrown towards the earth. The planet’s magnetic shield deflect a majority of these particles. However, the magnetic field at the poles is much weaker, and some particles enter the earth's atmosphere where they collide with gas particles. The collision results in the emission of light at the poles. The lights can extend from 50 miles to as high as 400 miles above the surface.
Occurrence of Auroras
Researchers have determined that the phenomena peaks in a cyclic pattern of 11 years or three years after a peak. However, Auroras occur almost every day although some are not visible. The last peak was in 2014, and the next is expected to be between 2025 and 2026.
Where To Watch the Northern Lights
Northern lights are visible from the southern and northern hemisphere. They create an irregular oval shape centered over either pole. In most instances, the south and north aurora are mirror-like. They occur at the same time, portray a similar shape, and have the same color. Since they occur close to the magnetic poles, the auroras sometimes extend southwards and can be seen in the western hemisphere as far as New Orleans. However, the eastern hemisphere never experiences the phenomena. The best place to watch the northern lights are in the Northwest Territories, Nunavut Yukon, and Alaska. The lights are also visible over the southern tip of Iceland and Greenland, northern Siberia, and the northern region of Norway. The southern auroras are not viewed by many because they concentrate around Antarctica and the southern edge of the Indian ocean.