Space
Weather
By Patrick
Barry and 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.
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.
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.
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.
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