Aurora Borealis - Northern Lights

 









Auroras are natural colored light displays in the sky, which typically occur in the ionoshere and are seen particularly in the polar region. They are the nature's own fireworks, apparently dancing across the dark sky. Aurora Borealis originate from sun. During large explosions and flares, huge quantities of solar particles (plasma clouds) are thrown out of the sun into the deep space. When these solar particles are closing in on earth, they are captured by earth's magnetic field and are guided towards Earth's two magnetic poles ( north pole and south pole). Down towards these magnetic poles, the solar particles are stopped by Earth's atmosphere. There they collide with the atmospheric gases present and the collision energy between the solar particle and the gas molecule is emiited as a photon (light particle). Thus, many such collisions causes an aurora.

The auroral lights' colors are determined by the spectra of gases in the Earth's atmopsphere, and the height at which the most collisions take place. Incoming particles tend to collide with different gases at different heights. Thus the green light occurs at the altitudes of 120 to 180 km, red light occurs at even higher altitudes, while blue and violet occur mostly below 120 km. The most common auroral forms and structures are Homogeneous arc, Arc with ray structure, Homogeneous band, Band with structure, Corona, Curtain etc.

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