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”
WHY ‘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
HOW DOES IT HAPPEN?
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! )
NORTHERN LIGHTS IN FICTION
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),
EARTH ISN’T THE ONLY ONE
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.
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