s8pe-41401-ca
10/31/05
7:10 PM
MAZER
Page 457
Solar Wind
Material in the Sun’s corona is
continually streaming out into space.
The electrically charged particles that
flow out in all directions from the
corona are called the solar wind.
The solar wind extends throughout
our solar system.
Most of the solar wind flowing
toward Earth is safely guided around
the planet by Earth’s magnetic field.
When solar-wind particles do enter the
upper atmosphere, they release energy, which can produce beautiful
patterns of glowing light in the sky. Such displays of light are called
auroras (uh-RAWR-uhz), or the northern and southern lights.
Auroras often occur near the poles.
This circular green aurora
occurred over Alaska
when particles from
the solar wind entered
the atmosphere.
Earth’s atmosphere usually prevents charged particles from reaching
the surface. However, during the peak of the sunspot cycle, flares and
other kinds of solar activity release strong bursts of charged particles
into the solar wind. These bursts, called magnetic storms, can disrupt
electric-power delivery across large regions by causing surges in power
lines. They can also interfere with radio communication.
Magnetic storms are much more harmful above the protective layers
of Earth’s atmosphere. Bursts of particles in the solar wind can damage
or destroy orbiting satellites. The solar wind also poses a danger to
astronauts during space flights.
check your reading
What causes auroras to form?
KEY CONCEPTS
CRITICAL THINKING
1. How does the Sun produce
energy? (8.4.b)
4. Analyze Why is the core the
only layer of the Sun where
energy is produced?
2. How does energy move from
the Sun’s core to the
photosphere? (8.4.b)
3. How does the solar wind
normally affect Earth? (8.4.b)
CHALLENGE
5. Compare and Contrast
Make a diagram comparing
sunspots, flares, and
prominences.
6. Infer A communications
satellite stops working while in
orbit, and a surge in an electric
power line causes blackouts in
cities across a large region.
What probably happened in
the Sun’s atmosphere shortly
before these events?
Chapter 14: Stars, Galaxies, and the Universe 457
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