Wednesday, 29 October 2014

The Auroras

The Auroras are a meteorological phenomenon that can be seen predominantly in the earth's high altitudes (Arctic and Antarctic). It is only possible to see the Auroras in the cold dark nights of winter, where the skies are clear and the moon is dull, creating the perfect conditions for these captivating light shows. The Auroras of the Arctic are known as the Aurora Borealis, literally meaning 'The northerly goddess of dawn'; whereas the Auroras of the Antarctic are known as the Aurora Australis, or 'The goddess of the south lands'. 

During the times of Medieval Europe the Auroras were considered to be a sign of God. In Norse mythology they were a sign of the Valkyrior (female figures of the sky who had the power to choose who may live and who may die during battle). It was believed that as the Valkyrior rode across the sky mounted proudly upon steeds, their armor shed an unusual flickering light that flashed gracefully upon the norther skies. The Cree (one of the largest tribes that inhabited North America and Canada) believed that the lights were caused by the dancing of spirits who inhabited the outer realms of earth. Ancient inhabitants of Greenland thought the lights were caused by either vast fires that filled the ocean, or by glaciers, which were emitting the energy they had stored from the sun during the day. You may not be surprised to find that none of these hypotheses were correct, and as per usual, there is a more scientific explanation.

The Auroras occur within what is know as the 'Aurora zone'. This zone is an area that sits over the magnetic poles of earth, with a radius of 2,500 km (approximately the distance from London to Namibia, Africa). In very basic terms, the beginnings of the Auroras start within the sun. As the sun burns with a surface temperature of 5,600 Celsius (10,000 Fahrenheit) explosions known as solar flares occur, releasing the equivalent energy of 160,000,000,000 megatons of TNT. These flares release electrons, protons, ions and atoms into space which travel as 'solar wind' towards earth for one or two days before making contact with the earth's magnetic field. Once the electrons and protons hit the magnetic field of earth, these charged particles then collide with the earth's more gaseous particles. Due to the power and number of collisions a large light source is created, and dependent upon the location of this light source it is named either the Aurora Borealis or the Aurora Australis.

The Auroras are usually seen as a pale yellowish-green, but on rare occasions they can also be seen in red, pink, blue or purple. The colour of the lights is dependent upon how high above the earth the lights are formed. Green signifies that the lights have been formed closer to earth (roughly 60 miles high), whereas red signifies that the lights have been formed high above the earth (roughly 200 miles high). Either way, no matter what the colour, no matter where the location, the Auroras truly are a natural wonder of the world.

An artist's impression of a solar flare exploding from the sun. This flare releases the same power as approximately 160,000,000,000 megatons of TNT.

An ancient depiction of the Valkyrior. In Norse mythology, these female goddesses were the cause of the Aurora Borealis.

The Auroras in action. The greenish colour of these lights suggests that they are formed close to the earth - roughly 60 miles away.

The Auroras as seen from space. This is a still-frame shot from a video recorded by the International Space Station.

- Until the next Butterfly...