The Aurora Borealis is a beautiful show of visible radiations created by nature that appear in the dark sky. “Aurora Borealis” . the Latin name of the dawn of the northern hemisphere. means the ruddy morning of the North. The name comes from the celebrated Italian scientist Galileo Galilei who. among other things. studied the visible radiations around the twelvemonth 1600. In Rome. were Galileo was populating. the ruddy colour dominates. but the most common colour is really greenish-yellow. which I will cover subsequently in the presentation. The Vikings in the twelvemonth 700-1000 called it merely “northern visible radiations. ” and in early England they called it “The Merry Dancers” mentioning to the manner the aurora moves.
Originating in the atmosphere high above the surface of the Earth. the northern visible radiations can be seen during dark hours in the polar parts of the northern hemisphere. There are similar visible radiations that appear in the southern hemisphere. The southern visible radiations and northern visible radiations are indistinguishable phenomenons. When you have a northern visible radiations show. you will besides hold an every bit big southern visible radiations show. The lone ground we don’t hear about southern visible radiations much is that there aren’t much colonies in Antarctica. Southern visible radiations occur around the geomagnetic South Pole. The scientific name for southern visible radiations is Aurora Australis.
The astonishing happening of the dawns really starts high above the earth’s atmosphere. The Sun emits a uninterrupted watercourse of ionised gas during its solar flairs. This gas consists of negatrons. protons and He karyon. The watercourse of gasses go forthing the Sun is known as the solar air current. As the solar air current attacks Earth. the atoms are influenced by the Earth’s magnetic field and are guided toward egg-shaped zones around the magnetic poles. The solar air current atoms so collide with air molecules in the upper ambiance. The hits impart energy to air molecules. chiefly O and N. and do them to breathe visible radiation. called the dawn.
The show of visible radiations occurs merely above heights of 80 kilometres and on occasion above 500 kilometres. The mean height is between 110 and 200 kilometres. Due to the nature of our magnetic field. the dawn can merely been seen in certain parts of the sky. The northern visible radiations exist in an ellipse shaped country called the dawn ellipse. and this egg-shaped rotates with its centre in the geomagnetic north pole. The size of this egg-shaped varies on an hourly footing with the sum of incoming solar atoms. The best observation sites of the dawn borealis are underneath the ellipse where there is the most geomagnetic activity. Geomagnetic energy is measured in Kp index. which is a graduated table from 0 to 9. A high Kp indicates a higher opportunity of auroral activity. One normally needs a Kp of about 3 to be capable to witness an dawn.
The ellipse normally occurs over northern parts of the Nordic states. including all of Greenland and Svalbard. northern parts of Alaska. Canada and Russia. Here one may detect northern visible radiations 90 % of the clip. which is about every clear dark dark. Though auroras occur all twenty-four hours. the day-side dawn has much weaker visible radiation than the night-side dawn. Strong daytime besides outshines the day-side dawn. so you will hold to detect the dawn during night- normally in the hours around midnight. Further down south observation clip decreases quickly as one reaches the outskirts of the aurora ellipse. Though the ellipse normally stays high in the Northern Hemisphere it does hold capablenesss to make parts of the southern United States. On November 6th. 2001. it reached down to Texas. and one time every 200th twelvemonth it goes all the manner down to the equator.
After old ages of entering the dawn. one has discovered that February. March and October enjoys a small spot more “aurora time” than other months. although this doesn’t mean dramatic shows won’t occur during other months. Dawns are more frequent late fall and early spring. Brilliant auroras frequently occur at 27-day intervals as active countries on the Sun’s surface face Earth during its 27-day rotary motion rhythm. Besides. the Sun has an 11 twelvemonth Sun topographic point rhythm. Every 11th twelvemonth the figure of musca volitanss extremum and the figure of solar atoms thrown out into infinite additions dramatically. Aurora activity remains high one to two old ages after this event. which is called Solar Maximum. We had solar upper limit around new twelvemonth. 2001. and the following is expected to happen around 2011 or 2012.
These visible radiations come in a fluctuation of colourss. The Sun radiates all seeable colourss. which is why sunlight appears white. The spectrum of seeable visible radiation associated with the dawn is much narrower. The dawn is caused by atoms of the solar air current clashing with atmospheric atoms and ions. The atmosphere consists chiefly of N and O. which when hit. emits characteristic colourss. The colourss that these gasses emit are green. ruddy. bluish. and xanthous. There are besides seven distinctions in the form that the dawns will take: Homogeneous discharge. discharge with beam construction. homogenous set. set with beam construction. drapes. beams. and aureole. These different forms and colourss form one of the earths greatest phenomenon’s that to this twenty-four hours go on to boggle the head of scientists and mundane society.
In the early twentieth century. auroral research focused on light emanation. height. distribution and colour. Today. scientists strive to understand the procedures that produce the assorted signifiers of the northern visible radiations and effort to explicate their alterations in clip and infinite. Scientists are particularly interested in the effects of solar activity on the Earth’s near-space. General involvement in possible planetary climatic alteration has increased in recent decennaries. Because atmospheric conditions in the heights of the dawn appear to hold a long-run consequence on conditions. auroral research has received heightened attending.