what is mean by aurora...how is it formed?

Question

is it a image caused due to falling of comets...
can you give me the basic(scientific) details about it..
where it can be seen .. during day or night time..
where this effect is occuring, inside or outside our admosphere?

Answer 1

The aurora is a glow observed in the night sky, usually in the polar zone. For this reason some scientists call it a "polar aurora" (or "aurora polaris"). In northern latitudes it is known as the aurora borealis, which is named after the Roman goddess of the dawn, Aurora, and the Greek name for north wind, Boreas, since in Europe especially it often appears as a reddish glow on the northern horizon as if the sun were rising from an unusual direction. The aurora borealis is also called the northern lights. The aurora borealis most often occurs from September to October and from March to April. Its southern counterpart, aurora australis, has similar properties.

Answer 2

The auroras occur around the north and south poles in auroral ovals, where the earth's magnetic fields interact with the solar wind. The farther you are from the poles, the worse your chances of seeing an aurora. The southern aurora is the Aurora Australius, the northern is the Aurora Borealis. Like the stars, the auroras still occur in the daytime, but due to the sunlight, we cant see them. Which is why you see auroras at night. It occurs within our atmosphere.

Without getting too technical, auroras are created by the atmosphere glowing as the charged particles of the solar wind stream along the earth's magnetic field lines. The auroras stretch throughout the upper limits of the atmosphere, stretching from about 40 miles above the earth to around 600 miles up. As the electrical energy created by the solar wind passes through the various bands of atmospheric gasses, those gasses glow different colors, and you have an aurora. As a bonus, you can actually get a fairly good idea of how high up the aurora is by what color(s) you're seeing. The oxygen at 60 miles or so above the earth glows bright yellow-green, and is probably the most commonly seen auroral tint. If you're quite lucky, you'll get a look at an all-red aurora, the result of high-altitude oxygen glowing about 200 miles overhead. More likely, you'll see a yellow-green aurora with maybe some blue from ionized nitrogen or a little red from neutral nitrogen, both usually seen around the auroral edges or ripples.

Answer 3

The aurora is now known to be caused by electrons of typical energy of 1-15 keV, i.e. the energy obtained by the electrons passing through a voltage difference of 1,000-15,000 volts. The light is produced when they collide with atoms of the upper atmosphere, typically at altitudes of 80-150 km. It tends to be dominated by emissions of atomic oxygen--the greenish line at 557.7 nm and (especially with electrons of lower energy and higher altitude) the dark-red line at 630.0 nm. Both these represent forbidden transitions of atomic oxygen from energy levels which (in absence of collisions) persist for a long time, accounting for the slow brightening and fading (0.5-1 sec) of auroral rays. Many other lines can also be observed, especially those of molecular nitrogen, and these vary much faster, revealing the true dynamic nature of the aurora.

Auroras can also be observed in the ultra-violet (UV) light, a very good way of observing it from space (but not from ground--the atmosphere absorbs UV).

Answer 4

Auroras are curtains of light generally found in the poles.It is created by the magnetism force of the earth.You can see it in the night or evening only in the poles.It is in the atmosphere in the 4th layer of the atmosphere known as ionosphere

Answer 5

The Earth is surrounded by atmosphere,of course,but there is an electromagnetic field arround the Earth.if sunrays collide in the field,some sort of energy is produced in the form of light.These lights are of many colours mainly green or red or blue.They are observed in polar region,not here in india,during night only.They do not harm us at all.

Answer 6

No, its not from comets. Here's some links that help define it:

http://www.its.bldrdoc.gov/fs-1037/dir-003/_0427.htm
http://www.thefreedictionary.com/aurora
http://www.geo.mtu.edu/weather/aurora/

Basically, the sun gievs off charged particles which stimulate particles in the atmosphere, giving it an odd, luminous, colored glow.


Hope this helps!

Answer 7

Read your book....or even try the library.