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The Question

(Submitted March 10, 1998)

I'm from White Bear Lake, Minnesota. I was flipping through the encyclopedia and I found an entry called "magnetic storms." I wanted to learn more about them. I've tried to find these answers using the school library, by searching your site and doing an Alta Vista search, but I'm not finding much, and the stuff I'm finding in encyclopedia is too confusing to understand. I hope you can help me answer these questions.

The Answer

A magnetic storm (or more correctly geomagnetic storm, or geomagnetic disturbance) happens when a pulse of particles and magnetic field from the Sun hits the earth (and it's magnetic field). This pulse is called a Coronal Mass Ejection (CME) and they are associated with solar flares, although they are not the same thing. When these CMEs hit the earth, they compress the Earth's magnetic field, and the changing magnetic field can create electricity in long metal objects such as oil pipelines (which makes them decay faster) and electric power lines. A 1989 power blackout in Ontario was caused by one of these geomagnetic storms. Magnetic storms also can effect radio communications, and the high energy particles that come along with them can damage satellites and even astronauts. They occur randomly, but are most common when the Sun has a lot of sunspots (it's "active" phase) every eleven years. They start at the Sun, but when they hit the earth, they span the whole globe, although they are worse close to the earth's magnetic poles. But people (other than astronauts) are completely protected by the earth's atmosphere, except for secondary problems such as blackouts.

The National Oceanic and Atmospheric Administration (NOAA) predicts magnetic storms, just as they predict hurricanes and the like, using data from spacecraft such as the Advanced Composition Explorer (ACE), which can see the CME before it hits the Earth.

For more information, you can look at Cosmicopia (http://helios.gsfc.nasa.gov/).

Also, the physics department at the U of Minnesota has a very good space physics/Aurora group.

They have an observatory very close to you. It is out by "Marine On St. Croix" and shares a site with the O'Brien astronomical observatory.

And they also have an active program where they give talks to schools, like your own. They might direct you to the current experts on this subject.

Thanks for your questions.

Eric Christian and Jonathan Keohane
for Ask an Astrophysicist

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