The polar lights, or “auroras”, that occur in both of the earth’s polar regions turn the heavens into a festival of lights of all shapes and colours that can be viewed with the naked eye. Well, wouldn’t you like to learn what’s behind this night-time luminescence?
The polar lights are natural phenomena and the clearest evidence of the sun’s effect on the earth’s atmosphere. The sun is actually a moving star as well as the earth’s source of heat and light. Various physical activities take place in the atmospheric layers of the sun. During the course of these activities, energized electrons, protons and certain heavy particles are scattered into space.
As the solar winds send these particles towards earth, they become caught up in the effects of the earth’s bipolar magnetic field. At first, this field does not allow the particles to enter; however, they manage to squeeze through weak magnetic fields at both poles, quickly picking up speed and hurtling straight towards earth. The particles collide in the upper layers of the earth’s atmosphere, exciting atoms and molecules.
Part of the energy released during this process is diffused through the earth’s atmosphere as light. These lights are known as the Polar Lights.
The polar lights can be seen in both hemispheres. The ones visible in the north are called the Northern Lights (Aurora Borealis), while those visible in the south are referred to as the Southern Lights (Aurora Australis). According to highly sensitive satellite measurements, these lights lie within the earth’s atmosphere at a height of 100-1,000 km above the earth, with the majority hovering around 100 km above the earth’s surface.
Horizontally, they can spread out for thousands of kilometers. The auroras can appear in different forms, including curtains, arcs, clouds, rays and fans. They can also take on different colours, either red or green, with green the most common. These interesting lights can quickly change their positions in the atmosphere, begin to glow, or instantly disappear.
These natural phenomena aren’t limited to light alone. Sometimes they include sound waves that are within the range of human hearing. The polar lights also store potential energy in the range of 40,000-50,000 volts.
Compare that to the 220 volts of electricity that comes from the outlets we use to charge our mobile phones, and it’s easier for us to get an idea of the immensity of the energy force stored in the skies.
IN BETWEEN THE PLANETS
The earth isn’t the only place where the natural phenomena of polar lights are visible; they can be seen from any planet that has a magnetic field and an atmosphere capable of trapping charged particles. Jupiter, Saturn and Uranus are the other planets in our own solar system where polar lights can be observed. For example, the polar lights of Jupiter occur when particles from its moon Io become trapped in Jupiter’s magnetic field.
The lights there are 1,000 times brighter than those found on earth. The polar lights of Saturn are very similar to those of earth, whereas the polar lights of Uranus are weaker than those of Saturn, but stronger than those of earth.
THE VAN ALLEN BELTS
The fiery magma and rapid rotation of the earth has produced magnetic belts that surround the planet. These belts are named after the American space scientist James Van Allen, who first identified them in 1958. These magnetic belts act as a shield to prevent harmful rays and particles emanating from the sun and other stars from reaching the earth. However, when solar activity is at its peak, these rays may penetrate the belts at both poles and keep moving towards the planet. The festive lights known as auroras are in fact charged particles that have passed through the Van Allen Belts and interacted with the atmosphere as they make their way towards earth.