June 2004
Space Weather
By Patrick L. Barry and Dr. Tony Phillips
Radiation storms, 250 mile-per-second winds, charged particles raining down from
magnetic tempests overhead ... it sounds like the extreme weather of some alien
world. But this bizarre weather happens right here at Earth.
Scientists call it "space weather." It occurs mostly within the gradual boundary
between our atmosphere and interplanetary space, where the blast of particles
and radiation streaming from the Sun plows into the protective bubble of Earth's
magnetic field. But space weather can also descend to Earth's surface. Because
the Earth's magnetic field envelops all of us, vibrations in this springy field
caused by space weather reverberate in the room around you and within your body
as much as at the edge of space far overhead.
In fact, one way to see these "geomagnetic storms" is to suspend a magnetized
needle from a thin thread inside of a bottle. When solar storms buffet Earth's
magnetic field, you'll see the needle move and swing. If you live at higher
latitudes, you can see a more spectacular effect: the aurora borealis and the
aurora australis. These colorful light shows happen when charged particles
trapped in the outer bands of Earth's magnetic field get "shaken loose" and rain
down on Earth's atmosphere.
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This image shows the outer solar
atmosphere, or corona, as viewed by the GOES 12 Solar X-ray Imager (SXI). It shows the plasma at 4.0 MK (million degrees Kelvin). Bright areas are associated with sunspots seen in white light images and may produce explosive events known as flares. Dark regions are coronal holes where the fastest solar wind originates. Image courtesy of the Space Environment Center/NOAA. |
And because a vibrating magnetic field will
induce an electric current in a conductor, geomagnetic storms can have a less
enjoyable effect: widespread power blackouts. Such a blackout happened in 1989
in Quebec, Canada, during a particularly strong geomagnetic storm. These storms
can also induce currents in the metallic bodies of orbiting satellites, knocking
the satellite out temporarily, and sometimes permanently.
Partly because of these adverse effects, scientists keep close tabs on the space
weather forecast. The best way to do this is to watch the Sun. The NASA/ESA SOHO
satellite and NOAA's fleet of GOES satellites keep a constant watch on the Sun's
activity. If a "coronal hole"--where high-speed solar wind streams out from the
Sun's surface--comes into view, it could mean that a strong gust of solar wind
is on its way, along with the geomagnetic storms it will trigger. And an
explosive ejection of hot plasma toward the Earth--called a "coronal mass
ejection"--could mean danger for astronauts in orbit. The advancing front of
ejected matter, moving much faster than the solar wind, will accelerate
particles in its path to near the speed of light, spawning a radiation storm
that can threaten astronauts' health.
Look for coming articles for more about space weather and about NOAA's efforts
to forecast these celestial storms. Meanwhile, read today's space weather
forecast at http://www.sec.noaa.gov/.
Kids can learn about the geostationary and orbits of the GOES satellites at
http://spaceplace.nasa.gov/en/kids/goes/goes_poes_orbits.shtml.
This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.