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AURORA

# What is the aurora?

On our earth, the aurora phenomenon occurs at the north poles and south poles. In the

northern hemisphere the aurora borealis is commonly known as the northern lights. In the

southern hemisphere the aurora australis is also know as the southern lights. This

phenomenon occurs when particles in solar winds are pulled into the atmosphere by the earths

magnetic force. The aurora is said to be continuously occurring between 1km and !km

abo"e the earths surface.

# What does an aurora looks like?

#urora can appear as long, narrow arcs of light, often e$tending east to west from

hori%on to hori%on. #t other times they stretch across the night sky in bands that fold, swirl and

e"en ruffle like curtains. They can spread out in multi colored rays, like "ertical shafts or light

that stretch far up into space. #nd sometimes they engulf the sky in a thin cloud or "eil. There

arent two identical aurora.

&ramatically different auroras can appear in the course of a single night, and all of the

forms can "ary in intensity. The late e"ening auroras are usually long diffuse arcs, which slowly

e"ol"e into rayed arcs or bands that show increasing acti"ity. #s the night progresses, the bands

and arcs become rippled and folded, e"entually breaking into rays and if the "iewer is lucky, a

corona. The corona is considered the most spectacular form of a rayed aurora, apparing o"erhead

with all shafts con"erging to a center point. 'atches(fluffy clouds of light and flickering auroras

are generally seen later in the night.

# When is the best time to see the aurora?

The aurora occurs all year round. The image of winter and aurora is strong, but you can

actually "iew the aurora during the summer. )owe"er, for some of the summer months in

*ellowknife and other locations with high latitude, the sun only goes down for a short while.

+ince it is still bright in the middle of the night it is not possible to see the aurora. urthermore,

during the autumn and spring, the weather is rather unstable and has a lower percentage of clear

skies. Therefore, we ha"e determined the best "iewing seasons to be from mid(#ugust to the endof +eptember and from mid(-o"ember to mid(#pril. In *ellowknife, it is possible to see the

aurora appro$imately / days of the year and when there are no obstructions such as hea"y

clouds, they almost always appear. #urora 0illage has calculated that each season, customers

who participate in consecuti"e days of aurora "iewing ha"e o"er a 2!3 chance of seeing the

aurora.

4hile some people may be concerned that a full moon is a problem, only weak aurora may be

obstructed by the light of the moon, but in *ellowknife the aurora is fre5uently strong enough

that aurora "iewing is still possible on a moonlit night. #s far as aurora photography goes, the

aurora abo"e a moonlit landscape actually tends to ha"e a pleasing effect. On the whole, whenparticipating in an aurora tour, one doesnt need to be worried about the moon.

# Where can you see an aurora?

#uroras usually occur in ring(shaped areas about /, km 6,! miles7 in diameter

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around the magnetic poles of the 8arth. These rings are known as auroral o"als. The northern

o"al traces a path across central #laska and 9anada, :reenland, and northern +candina"ia and

;ussia. In the southern hemisphere, the auroral o"al ho"ers mostly o"er the oceans circling

#ntarctica, but it can occasionally reach the far edges of -ew ut it wasnt until the +pace #ge, when satellites could gather images of the

entire 8arth, that scientists were able to see the large(scale auroras around both poles at the same

time.

# Why do auroras come in different colors and shapes?

The color of the aurora depends on which gas, o$ygen or nitrogen, is being e$cited by the

electrons, and on how e$cited it becomes. The color also depends upon how fast the electrons are

mo"ing, or how much energy they ha"e at the time of their collisions. )igh energy electrons

cause o$ygen to emit green light 6the most familiar color of the aurora7, while low energy

electrons cause a red light. -itrogen generally gi"es off a blue light. The blending of these colors

can also lead to purples, pinks, and whites. The o$ygen and nitrogen also emit ultra"iolet light,

which can be detected by special cameras on satellites.

The different shapes of auroras are a mystery that scientists are still trying to unra"el. The

shape seems to depend on where in the magnetosphere the electrons originate, what causes them

to gain their energy, and why they di"e into the atmosphere.

# How does the aurora occurs?

#urora occurs when the +un sends off matter we call particles to the empty space. These

particles are charged and contain energy, which means they contribute to electricity. These

particles flying in space are called ?solar wind?. +ometimes the solar wind hits 8arth. 8arth has

a protection shield of energy around it. This is called the ?magnetic field? and forms anelongated sphere around the 8arth called the ?magnetosphere?. The magnetic field wards off

most of the solar wind. #t high(latitude areas 6polar areas7, the magnetic field is less powerful,

and cannot protect 8arth from the solar wind. There the particles of the solar wind and coming

from the magnetosphere may hit the particles of the air 68arth@s atmosphere7. 4hen they hit, the

atmosphere is heated and e$cited and the e$cess energy gets away, a phenomenon which we see

as mo"ing lights in the sky abo"e 1 km altitude typically. #n aurora can also occur following

a solar e"ent called a coronal mass e=ection 69A87, when the charged particles rip through the

electromagnetic field because of their power.

# Do other planets have auroras?

#uroras ha"e been obser"ed on Bupiter, +aturn, and Cranus, but not on Aars, 0enus, or

Aercury. #ny planet with a magnetic field and an atmosphere should likely ha"e auroras 6Aars

and 0enus ha"e no global magnetosphereD Aercury has almost no atmosphere7. +ince an aurora

indicates the presence of an atmosphere, we might be able use the presence of auroras to find

planets beyond our solar system that could support life.

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umber!

http://www.auroravillage.com/aurora_facts.html

httpEFFsimple.wikipedia.orgFwikiF#urora

httpEFFwww.northernlightscentre.caFnorthernlights.html

httpEFFwww.e$ploratorium.eduFlearningGstudioFaurorasFhappen.html httpEFFwww.gi.alaska.eduF

pwg.gsfc.nasa.go"FpolarF8'OFauroralGposterFauroraGallGnasa

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