17 April 2015

Natural beauty: Story of the Aurora

As shown in movies and images from satellites, Earth appears to be a blue ball floating around in space. Is that the final reality?
 Ever thought of what it would be like to paint a rubber ball with various colours? What the ball will look like? Now imagine painting the surface of the earth with coloured streaks, and how this will appear to the satellites.
A glimpse of what it will look like :
Yes this is what is called brilliance, this is what is called the Aurora Borealis or commonly referred to as “Northern lights”


·        These occur at the geomagnetic poles in a band known as auroral zone, which stretches between 10° and 20° from the poles with a typical width of 3° to 6° wide (in latitude) at all local times, most clearly visible in the dark.
·        Auroral zone- a ring-shaped region with a radius of approximately 2500 km around the Earth's magnetic pole. It was hardly ever seen near the geographic pole, which is about 2000 km away from the magnetic pole.
·        Magnetic midnight is the time of day when the North or South Magnetic Pole is exactly in between the sun and an observer on earth's surface. This is best time for observing auroras. Because Earth's magnetic poles do not coincide with its geographical poles—the angle between Earth's rotation axis and magnetic axis is about 11°–magnetic midnight differs from conventional midnight. In most of the United States, magnetic midnight occurs about an hour earlier


The auroras, surrounding the magnetic pole occur when highly charged electrons from the solar wind interact with elements in the earth's atmosphere. Solar winds stream away from the sun at speeds of about 1 million miles per hour; hit the electrons in the earth’s upper atmosphere and generate coloured patterns ( At altitudes from 20 to 200 miles above the earth’s surface the atmosphere contains oxygen and nitrogen atoms)
The colour of the aurora depends on which atom is struck by these electrons, and the altitude of the meeting.
·         Green - oxygen, up to 150 miles in altitude
·         Red - oxygen, above 150 miles in altitude
·         Blue - nitrogen, up to 60 miles in altitude
·         Purple/violet - nitrogen, above 60 miles in altitude

All of the magnetic and electrical forces react with one another in constantly shifting combinations. These shifts and flows can be seen as the auroras "dance," moving along with the atmospheric currents that can reach 20,000,000 amperes at 50,000 volts ( a 100000 times more than what is required at our homes! ) 


So much significance, so many movies with the same name; must be something important, think about it?
·         Northern Lights (1978 film)
·         Northern Lights (1997 film)
·         Northern Light (film), a 2006 Dutch film
·         The Golden Compass (film), a 2007 film adaption of the 1995 Philip Pullman novel
·         Northern Lights (2009 film),


Other planets observed to witness auroras are :
·        Both Jupiter and Saturn have magnetic fields much stronger than Earth's and both have extensive radiation belts. Auroras have been observed on both, most clearly with the Hubble Space Telescope.

·        Uranus and Neptune have also been observed to have auroras.
·        These auroras have also been observed on Venus and Mars. Because Venus has no intrinsic (planetary) magnetic field, Venusian auroras appear as bright and diffuse patches of varying shape and intensity, sometimes distributed across the full planetary disc. Venusian auroras are produced by the impact of electrons originating from the solar wind and precipitating in the night-side atmosphere.