Aurora borealis 2
Aurora borealis 2INTRODUCTION
One of nature=s most spectacular phenomenons to date is the once mysterious aurora. This dazzling show of lights has been working its magic for people around the world for several years. But, few know the cause of this amazing light display. It is the purpose of this report to reveal this mysteryC a mystery that scientists aspired to solve for nearly 300 years.
WHAT IS AN AURORA?
An aurora is a luminous atmospheric phenomenon that can be seen most frequently above 60� North or South latitude, and sometimes spills over to other parts of the world. It consists of rapidly shifting patches and dancing columns of light of various colours. Dramatic displays occur around spring and fall equinoxes but the aurora can be seen any cloudless night, the best time being around midnight in the winter. It is named according to its location, Aurora Borealis meaning the northern lights, and Aurora Australis meaning the southern lights. The general name for both is Aurora PolarisC since both displays occur at the earth=s poles.
WHAT CAUSES AN AURORA?
For many years, the ideas about what causes an aurora were left to old legends and unsubstantiated theories. The inuit believed that the northern lights were the spirits of dead relatives, dancing around in the sky, while the Vikings believed that they were caused by a fire on the edge of the world. In the fourteenth century, Aristotle described the auroras as jumping goats caused by the earth=s vapours being set on fire by meteors. Later on, in 1707, a Norwegian physicist claimed that they were caused by steam and smoke that escaped from a heat source beneath Greenland. It was not until the late 1950's that scientists finally discovered the true cause of the aurorasC Solar Wind.
Solar Wind
Approximately every eleven years, explosions erupt from sun spots creating what are called Solar Flares. These flares can extend tens of thousands of kilometres high and reach temperatures of 20 million degrees Celcius. They also propel Solar Wind, which is a stream of radiation and plasmaC a spray of charged particles. This solar wind, which can travel through space at 1-3 million km/h, approaches and threatens earth two to three days after leaving the sun. At approximately 65,000 km from the earth=s surface, the wind encounters=s the earth=s magnetic field. Most of it is deflected by the field while some leaks in where the magnetic field lines enter the earthC the earth=s magnetic poles. Since the solar wind carries the sun=s magnetism with it, the portion that leaks in reacts with the earth=s magnetic field lines, producing electric power. This newly produced stream of electrons, now named Birkland=s Currents, follows the earth=s field lines into the north and south poles.
When 10,000 km above ground, the Birkland=s Currents begin to shape like curtains and begin to accelerate. At about 100-200 km from ground,...
To view the complete essay, you be registered.