Shaped by Earth's magnetic field

When viewed from space, the aurora appears as a bright oval around both the geomagnetic pole(S) in the Northern hemisphere and the geomagnetic pole (N) in the Southern hemisphere. The auroral oval, and the auroral curtain you see above you, are shaped by Earth's magnetic field.

Earth is a giant magnet
An invisible field of magnetic force surrounds every magnet including Earth. Every magnet has a north and south pole. Compass needles point north because their N ends are attracted by Earth's magnetic S pole in the northern hemisphere.

Earth's rotation causes its molten metal core to rotate. The movement of the core generates electricity which in turn generates Earth's magnetic field. The other magnetic planets in our solar system are Jupiter, Saturn, Uranus, and Neptune.


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Auroral oval
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Magnetic Earth
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The magnetosphere protects Earth
The solar wind -- streams of charged particles flowing from the sun -- is deflected by Earth's magnetic field. Earth's magnetic field is in turn compressed by the solar wind and distorted into a comet-shaped cavity known as the magnetosphere. The magnetic fields can intermingle creating a complicated flow pattern within the magnetosphere.



Helpful links:

"Exploration of the

"A Beginner's Guide
to the Magnetosphere"

Gigantic natural generator
Generators produce electricity by moving a conductor across a magnetic field. When the solar wind (plasma is very conductive) blows past the magnetosphere (Earth's magnetic field), it generates as much as a million megawatts of electricity. A small part of this electricity causes discharge in the polar upper atmosphere and creates light much in the same way a neon sign creates light. This discharge-created light that we observe is the aurora.


Oscilloscope &
aurora diagram
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Celestial oscilloscope
The inner workings of an oscilloscope parallel the auroral mechanism and can be helpful in understanding how the aurora moves. When an oscilloscope is turned on, it produces a thin beam of electrons. This beam strikes fluorescent material coating the screen. This material emits light and produces the image seen on the screen. In the case of the aurora, high energy electrons are striking gas molecules and producing an image in the upper atmosphere.
Electrons are negatively charged and, like a magnet, are repelled by negative charges and attracted to positive charges (opposites attract). Thus, charged plates in the oscilloscope can control beam movement by deflecting the electron beam.
A complicated control system can produce a cylindrical beam that shows up as a circle on the screen. Auroral scientists have discovered that this process is similar to the process that forms the auroral oval. Interactions between Earth's electric field, the solar wind, and Earth's magnetic field push and pull the high energy electrons striking Earth's upper atmosphere to create the undulating movements of the auroral curtain.


A simplified oscilloscope
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movie (15kb)


Geophysical Institute
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site last modified: August 2003 maintained by Asahi Aurora Web Author