The aurora borealis offers an entrancing and mesmerizing display of lights in the night sky that amaze everyone who see it. It is a unique and splendid creation of Mother Earth herself. Apart from its stunning beauty, the aurora borealis is a combination of physical concepts blending together to bring about a fascinating phenomenon. An aurora is referred to as polar lights. The term “aurora borealis” indicates the aurora seen in the northern hemisphere while the aurora occurring in the southern hemisphere is known as the “aurora australis”. The dazzling dancing lights are the result of disturbances in the magnetosphere caused by solar wind and are predominantly seen in the high-altitude regions of the world.
Causes of the Aurora Borealis
The sun is about 93 million miles away from the earth. But its effects of great storms release gusts of charged solar particles hurtling across space. A continuous stream of energetic particles known as the solar wind are carried out into space from the sun along the magnetic field lines and strike the gaseous particles in the earth’s upper atmosphere. These particles not only cause beautiful display of auroral lights but also create hazardous weather conditions in space including power grid outrages, communication blackouts, etc. The earth is protected by its magnetic field called the magnetosphere and most of the energetic particles get deflected. When the solar particles manage to enter the earth’s magnetic shield they are accelerated down the magnetic field lines to the poles where they hit the gaseous particles in the earth’s atmosphere.
Sunspots are the regions of highly concentrated magnetic field, thousands of times that of the Earth’s magnetic field. These usually appear in pairs and cause large scale eruptions and mass ejections. These eruptions are huge bubbles of plasma interweaved with magnetic field that are launched into space at speeds up to several million miles an hour and can also cause huge geomagnetic storms. The auroras appear most magnificent when the sun is more active.
The color of the auroral display depends upon the wavelength of the emitted light. When solar particles enter the earth’s atmosphere and collide with atoms and ions, their outer electrons are promoted to higher levels of energy and they become excited. When the electrons return to their original energy levels the light is emitted at a certain wavelength depending upon the transition. A certain color will be visible in the electromagnetic spectrum depending on the presence of a kind of molecule. The most prominent color exhibited by the aurora is green because of oxygen molecules. The red light appears due to collision between oxygen and nitrogen molecules while blue and purple are seen because of nitrogen.
Conditions and Places to Observe the Auroras
The suitable conditions for observing such celestial scenes are dark and moonless nights. Seasons of long wintery nights, Near Equinoxes in March and September also play an important role in viewing the auroras. Such significant factors persist in places like Iceland, Fairbanks in Alaska, Yellowknife in Canada, Norway, Northern Sweden and Finland, Greenland, Tasmania and New Zealand.