Astronaut Don Pettit creates a time lapse video of the Aurora Borealis from the International Space Station. NPR Science Friday, April 10, 2009.
What is the Aurora Borealis?
The Aurora Australis over Antarctica, as seen from space.
What causes auroras?
Some fun facts about the Aurora:
You can learn more about auroras and the Earth's magnetic field at Windows to the Universe.
©2009 Tammy Yee
What is the Aurora Borealis?
Auroras are brilliant curtains of light most often seen in the polar regions. In the north they are called the Aurora Borealis (Aurora, after the Roman Goddess of Dawn, and Borealis, Greek for "north wind") and are most often seen from September to October and from March to April. In the south they are called the Aurora Australis (Australis, Latin for "south"), and can best be viewed from September to May.
What causes auroras?
Molten iron swirling deep within the Earth creates a magnetic field around the planet. If you can imagine a giant bar magnet inside the Earth, the ends are where the magnetic north and south (or positive and negative) poles would be. Magnetism is a force which attracts magnetized objects, just as a magnet attracts paperclips or iron filings. The Earth's magnetic field draws particles along magnetic field lines, toward the magnetic poles:
When solar winds bombard the Earth with ions, these charged particles move along the magnetic field lines toward the magnetic poles. When these particles strike our atmosphere, they erupt in spectacular displays of light, what we call the auroras.
Photo by Senior Airman Joshua Strang, U.S. Air Force (from Wikipedia).
Some fun facts about the Aurora:
- Solar winds drive particles toward the Earth at about a million miles per hour. It takes 40 hours for these particles to strike the Earth's atmosphere.
- The Earth's magnetosphere shields us from these particles; if not for this shield, life on Earth would be very different.
- The colors of the aurora result when charged particles from the sun strike atoms in our atmosphere:
* 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
You can learn more about auroras and the Earth's magnetic field at Windows to the Universe.
©2009 Tammy Yee