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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
Questions on this topic are no longer responded to by the "Ask an Astrophysicist" service. See http://imagine.gsfc.nasa.gov/docs/ask_astro/ask_an_astronomer.html
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