Misconceptions and Facts about the Aurora and its Causes | Slides Astrophysics

Popular myths about

the aurora

AboutPolar

For more information:

Popular myths about

the aurora

The following are common misconceptions about the aurora:

•Auroras are caused by sunlight reflecting off of the polar ice cap.

•Auroras are caused by moonlight reflecting off of ice crystals in the

atmosphere.

•Auroras are caused by electrons arriving directly from the Sun and

guided by Earth’s magnetic field into the polar atmosphere.

In any of these cases, the aurora would look very different from the

beautiful displays we see.

About Polar

NASA’s Polar spacecraft was launched on February 24, 1996, to obtain

data from the regions over the poles of the Earth. From an orbit that

carries it over both poles at least once a day, the spacecraft gathers

images of the aurora and studies Earth’s interaction with the solar wind,

as well as the physical processes that transfer particles and energy into

and through the magnetosphere. http://istp.gsfc.nasa.gov/istp/polar

For more information:

Web sources:

The Exploration of the Earth’s Magnetosphere

http://www.phy6.org/Education/Intro.html

The Aurora Explained

http://www.alaskascience.com/aurora.htm

Windows to the Universe

http://www.windows.ucar.edu/spaceweather/

Mission to Geospace

http://istp.gsfc.nasa.gov/istp/outreach

Print sources:

Asgeir Brekke and Alv Egeland. The Northern Light: From Mythology to Space

Research. New York: Springer-Verlag, 1983.

Michael Carlowicz and Ramon Lopez. Storms from the Sun - The Emerging Science

of Space Weather. Washington, DC: The Joseph Henry Press, 2002.

Robert Eather. Majestic Lights: The Aurora in Science, History, and the Arts.

Washington, DC: AGU, 1980.

Sten Odenwald. The 23rd Cycle - Learning to Live with a Stormy Star. New York:

Columbia University Press, 2000.

Kenny Taylor. Auroras, Earth’s Grand Show of Lights. National Geographic,

200(5), 2001.

Why is the aurora

important?

Do other planets

have auroras? National Aeronautics and

Space Administration

Goddard Space Flight Center

Greenbelt, Maryland 20771

Polar Mission, Mail Code 696

Why is the aurora

important?

The aurora is the only visible evidence that the Sun and the Earth are a

system connected by more than sunlight.

The Sun’s corona continuously emits a solar wind, a stream of electrically

charged particles (mostly protons and electrons) flowing out in all

directions. These particles interact with Earth's magnetic field (right side

of figure), which reaches far into space. Most of the particles from the

Sun are deflected by the magnetic field, creating a huge cavity in the

solar wind. This cavity is called the magnetosphere, and it stretches

about 60,000 kilometers on the day side (toward the Sun) and several

hundred thousand kilometers in a long tail on the night side.

Under certain conditions more of the energy carried by the solar wind

can enter the magnetosphere. Here the energy is converted into electric

currents and electromagnetic energy and temporarily stored.

This higher energy state of the magnetosphere is unstable and the

energy of the currents can be released suddenly. Some of this energy

accelerates electrons in the magnetosphere and causes them to spiral

down the Earth’s magnetic field into the atmosphere, where they

produce the aurora. By studying the patterns of auroral light, scientists

can obtain a picture of what is happening in the huge magnetosphere.

Do other planets

have auroras?

Auroras have been observed on Saturn

(image), Jupiter, and Uranus. Any planet

with a magnetic field and an atmosphere

should likely have auroras.

NP-2002-5-459-GSFC

Steele Hill

J.T. Trauger (JPL) and NASA

NASA

Aurora Brochure 6/11/02 7:50 AM Page 1

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For more information: , About Polar • The following are common misconceptions about the aurora:the aurorathe auroraPopular myths aboutPopular myths about

Auroras are caused by sunlight reflecting off of the polar ice cap.

atmosphere.Auroras are caused by moonlight reflecting off of ice crystals in the

guided by Earth’s magnetic field into the polar atmosphere.Auroras are caused by electrons arriving directly from the Sun and

and through the magnetosphere.as well as the physical processes that transfer particles and energy intoimages of the aurora and studies Earth’s interaction with the solar wind,carries it over both poles at least once a day, the spacecraft gathersdata from the regions over the poles of the Earth. From an orbit that NASA’s Polar spacecraft was launched on February 24, 1996, to obtain About Polarbeautiful displays we see.In any of these cases, the aurora would look very different from the

http://istp.gsfc.nasa.gov/istp/polar

The Exploration of the Earth’s Magnetosphere Web sources: For more information:

http://www.phy6.org/Education/Intro.html The Aurora Explained http://www.alaskascience.com/aurora.htm Windows to the Universe http://www.windows.ucar.edu/spaceweather/ Mission to Geospace http://istp.gsfc.nasa.gov/istp/outreach

Asgeir Brekke and Alv Egeland. Print sources:

The Northern Light: From Mythology to Space Research. (^) New York: Springer-Verlag, 1983. Michael Carlowicz and Ramon Lopez. (^) Storms from the Sun - The Emerging Science of Space Weather. (^) Washington, DC: The Joseph Henry Press, 2002. Robert Eather. Majestic Lights: The Aurora in Science, History, and the Arts. Washington, DC: AGU, 1980. Sten Odenwald. (^) The 23rd Cycle - Learning to Live with a Stormy Star. (^) New York: Columbia University Press, 2000. Kenny Taylor. Auroras, Earth’s Grand Show of Lights. National Geographic, 200(5), 2001.

have auroras? Do other planets. important? Why is the aurora

Polar Mission, Mail Code 696 Greenbelt, Maryland 20771 Goddard Space Flight Center Space AdministrationNational Aeronautics and

solar wind.Sun are deflected by the magnetic field, creating a huge cavity in theof figure), which reaches far into space. Most of the particles from thedirections. These particles interact with Earth's magnetic field (right sidecharged particles (mostly protons and electrons) flowing out in allThe Sun’s corona continuously emits a solar wind, a stream of electricallysystem connected by more than sunlight. The aurora is the only visible evidence that the Sun and the Earth are aimportant? Why is the aurora

This cavity is called the magnetosphere, and it stretches

should likely have auroras.with a magnetic field and an atmosphere(image), Jupiter, and Uranus. Any planet Auroras have been observed on Saturnhave auroras? Do other planetscan obtain a picture of what is happening in the huge magnetosphere.produce the aurora. By studying the patterns of auroral light, scientistsdown the Earth’s magnetic field into the atmosphere, where theyaccelerates electrons in the magnetosphere and causes them to spiralenergy of the currents can be released suddenly. Some of this energyThis higher energy state of the magnetosphere is unstable and thecurrents and electromagnetic energy and temporarily stored.can enter the magnetosphere. Here the energy is converted into electricUnder certain conditions more of the energy carried by the solar windhundred thousand kilometers in a long tail on the night side.about 60,000 kilometers on the day side (toward the Sun) and several

NP-2002-5-459-GSFC J.T. Trauger (JPL) and NASA Steele Hill NASA

What causes the aurora?

Can you hear the aurora?southern hemisphere?Do auroras exist in the be seen?Where can the aurora

Why the different shapes? Why the different colors?

upperbetween fast-moving electrons and the oxygen and nitrogen in Earth’s The typical “northern lights,” or aurora borealis, are caused by collisionsWhat causes the aurora?

atmosphere. The electrons

which come from the can emit enough light for the eye to detect.When a large number of these collisions occur, the oxygen and nitrogenemit photons, small bursts of energy in the form of light.“excited.” As they “calm down” and return to their normal state, they- transfer energy to the oxygen and nitrogen gases, making themmagnetosphere, the region of space controlled by Earth’s magnetic field This ghostly light will in the daytime.aurora is much dimmer than sunlight, it cannot be seen from the groundthe light comes from altitudes between 60 and 200 miles. Since theproduce the dance of colors in the night sky we call the aurora. Most of

shaped Auroras usually occur in ring-be seen? Where can the aurora

areas circling the Themagnetic poles of the Earth. rings expand and andin central Canada, Alaska,places to see auroras areauroral activity. The bestcontract with the level of Greenland, northern

the ovals.shows the simultaneous “crowns” ofPolar spacecraft in ultraviolet lightaurora australis). This picture from thethe southern magnetic pole (known as Yes - an auroral oval also exists aroundsouthern hemisphere? Do auroras exist in thesunlit Earth.light by NASA’s Polar satellite and superimposed on a figure of a partlycan only be seen from outer space. This image was taken in ultravioletfar south as Florida or Texas. An entire ring, called the auroral oval,On rare occasions, they can be seen asScandinavia and northern Russia.

Simultaneous ovals are

scientists have been unable to detect any.where auroras are formed is too thin to even conduct sound, andthey have heard crackling, swishing, and hissing sounds. But the air Observers have speculated about this for hundreds of years, noting that Can you hear the aurora?nearly mirror images of each other.

Why the different colors?

beingoxygen or nitrogen - isdepends on which gas - The color of the aurora excited by the electrons, and on how excited it becomes. Oxygen produce purples, pinks, and white.light. The blending of these colors can alsolight; nitrogen generally gives off a bluemost familiar color of the aurora) or a redemits either a greenish-yellow light (the The

Scientists are still trying to answer this question. Why the different shapes?human eye.cameras on satellites but not by thelight, which can be detected by specialoxygen and nitrogen also emit ultraviolet

The shape of the of a single night.atmosphere. Dramatically different shapes can be seen over the courseand on the processes that cause the electrons to precipitate into theaurora depends on the source of the electrons in the magnetosphere Polar/VIS, NASA/U. Iowa Polar/VIS, NASA/U. Iowa Michel Tournay Jan Curtis Jan Curtis Jan Curtis Jan Curtis Jan Curtis Background image: Jan Curtis

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