The Holy Grail of skywatching- The Northern lights
The northern lights are natural and an atmospheric phenomenon that is considered the Holy Grail of skywatching. An aurora is a mesmerizing display of natural lights that dazzle in the sky generally at night. Polar lights (aurora polaris) are a natural occurrence of shimmering light in the sky mostly seen at night in both the northern and southern hemispheres which can be an absolutely rare spectacular sight. Northern lights are also known by their scientific name, aurora borealis, and southern lights are also known as aurora australis.
The northern lights are not seen for the very first time in the history of mankind rather the earliest record of the northern lights is evident in a 30,000-year-old cave painting in France. A well-known scientist and astronomer, Galileo Galilei coined the term “aurora borealis” in 1619, after the Roman goddess of dawn, Aurora, and the Greek god of the north wind, Boreas. Aurora borealis is termed for the northern lights in the northern hemisphere while, in the southern hemisphere, they are known as the southern lights or Aurora Australis.
The temperature at the surface of the sun is millions of degrees Centigrade. At this temperature, the gas molecules colliding with each other are frequent and explosive. The origin of aurora begins at the photosphere when solar activity ejects a cloud of gas. This activity is known as a coronal mass ejection (CME). Free electrons and protons are expelled from the sun’s atmosphere by the rotatory motion of the sun and escape through holes in the magnetic field. The earth’s magnetic field is weaker at either pole and therefore some particles enter the earth’s atmosphere, taking about 2 to 3 days, it collides with the Earth’s magnetic field. It is an invisible field, and if its shape is formed, it would make Earth look like a comet with a long magnetic ‘tail’ stretching a million miles behind Earth in the opposite direction of the sun. Blown towards the earth by the solar wind, the charged particles are mostly deflected by the earth’s magnetic field. When a coronal mass ejection collides with the magnetic field, it causes multiplex changes to happen to the magnetic tail region. These changes generate a stream of charged particles (current), which then flow along lines of magnetic force into the Polar Regions. These particles are boosted in energy in Earth’s upper atmosphere, and when they collide with oxygen and nitrogen atoms, they produce dazzling dancing auroral light.
The Northern lights, Aurora generally extend from 50 miles (80 kilometres) to a maximum of 400 miles (640 kilometres) above the earth’s surface.
Northern Lights can be seen in the northern or southern hemisphere, in an irregular oval shape centred over each magnetic pole (North and South). Scientists have explained that in most instances northern and southern auroras are mirror-like images that occur at the same time, with similar shapes and colours.
Auroral displays appear in many colours although pale green and rose pink are the most common. Shades of red, yellow, green, blue, and violet have also been observed. The lights appear in many forms from patches, isolated or scattered clouds of light to streamers, arcs, rippling curtains, or shooting rays that light up the sky with an eerie glow.
The phenomena occur at the magnetic poles, northern lights have been seen as far south as New Orleans in the western hemisphere, while similar locations in the east had never experienced the mysterious lights. However, the best places to gaze the lights (in North America) are in the northwestern parts of Canada, particularly the Yukon, Nunavut, Northwest Territories, and Alaska. Auroral displays can also be glared upon over the southern tip of Greenland and Iceland, the northern coast of Norway, and the coastal waters in the north of Siberia. Southern auroras are not often seen as they are concentrated in a ring design in the sky around Antarctica and the southern Indian Ocean.
