In certain polar regions of the earth, a rare and fascinating phenomenon occurs in the dark season of winter. This phenomenon is called the Northern Lights, or auroras. In areas where auroras can be seen, the sun shines brightly for six months and then disappears for the next six. The sun follows a straight path across the sky, rising in the north and setting in the south. This is because of the latitude of these regions. Unlike other regions of earth, the polar regions either completely face the sun or don’t face it at all. During the first six months of the long, endless nights of dark winter, auroras are frequently seen, almost every night, in fact. During the rest of the year, the summer months, when the sun is up even in the middle of the night, auroras can only be viewed by using complicated scientific telescopes. These auroras are produced by a series of solar reactions, they have given scientists much to study, and ordinary people the basis of many myths and legends.
Long ago, in an effort to explain auroras, people made up their own myths and legends to explain them. Auroras were a power which they feared and respected. Some thought that there was a direct connection between natural disasters like droughts and volcanic eruptions and the occurrence of an aurora. Others thought they were the souls of women who died virgins. Still others thought they were the frozen wings of swans and other birds.
However, modern science has shown that the scientific cause behind an aurora is very complicated and affected by certain climate conditions. The process starts in the sun, where high energy particles are blown away and escape the sun’s magnetic field and surface in a “high vacuum electrical discharge”. These particles accelerate at high speed in “an ever widening spiral” called the garden hose effect, because it resembles water coming out of a garden hose that rotates above a person’s head. In about three days, the particles reach earth, but they are stopped by the earth’s magnetic field and encase the earth in “ a comet-shaped cavity called the magnetosphere”. The comet shape is compressed on the daylight side and drawn out into a tail-like shape on the night time side. Since the open magnetic field lines are weak only in polar regions, the particles accelerate towards them. The high energy particles collide with air molecules, which causes their speed energy to change to light energy. During the collision they are discharged and then either ionized or neutralized, depending on whether a particle is neutralized or ionized, determines the color of an aurora.
With regard to the color of the aurora, there are many more aspects which affect their color. The altitude, speed and charge (ionized or neutral) at which energy and air particles collide set the shades of the auroras. Every atmospheric gas produces a different color, when high energy particles collide with it. The brightest and most commonly occurring is “yellow-green” caused by oxygen atoms at an altitude of about 60 miles. The rarest color, red, is also caused by oxygen atoms but at a higher altitude, around 200 miles. Other atmospheric gases such as ionized nitrogen produce a blue colored light, while neutral nitrogen atoms create a “purplish-red” color.
Finally, auroras usually occur in the magnetosphere and are formed by reactions in the sun called sun storms or sun spots which produce, great amounts of energy both from the sun’s particles and from the collisions that occur in our magnetosphere and ionosphere. Millions of watts of power are generated in the charging and discharging processes in the auroras which may disrupt communication waves transmitted in the ionosphere. They can also cause other serious damage like corrosion in the trans-Alaska pipeline and disruption of military and navigational equipment.
Studying auroras and the areas where they occur can be very useful for scientists, because they can discover correlations with climate changes in the world. In Norway, in the city of Troms? where auroras are frequent there are many laser telescopes to observe them day and night. Sometimes when a volcano erupts in a faraway island, by using telescopes with light enhancements, the thin clouds that rise can be seen reflected in auroras in the arctic regions. It is also known that in the 17th century, when no Northern Lights were seen, the Norwegian region had very bad climate conditions. Scientists are now trying to find if there was a connection between auroral and climate patterns. Norwegian cities are a typical location for many busy research labs, making it easier to launch rocket-mounted telescopes into space, and more easily view the auroral patterns.
Auroras are not only a dark mystifying and rare phenomenon, they also raise many questions that still have to be studied closely. They stunned mankind long ago and demanded respect, even though mankind never reached the right conclusion as to what these natural light shows really were. Scientists are still looking for answers. Large populations that live in close range to volcanoes or other dangerous areas can be saved in time. Who knows if they will find out if natural disasters can be predicted?
The Northern Lights – Aurora Borealis