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Chapter 29.2
Solar Activity
Sunspots
•
sunspot a dark area of the
that has a strong magnetic field.
•
The movements of gases within the sun’s
sun’s rotation produce magnetic fields.
•
These magnetic fields cause convection to
•
Slower convection causes a
in the amount of gas that is transferring energy from the core
of the sun to these regions of the photosphere.
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Because less energy is being transferred, these regions of the photosphere are considerably cooler than
surrounding regions, and form areas of the sun that appear
than their surrounding regions.
•
These, cooler, darker areas are called
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The rest of the photosphere has a grainy appearance called
of the sun that is cooler than the surrounding areas and
zone and the movements caused by the
in parts of the convective zone.
.
.
The Sunspot Cycle
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Observations of sunspots have shown that the sun rotates.
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The numbers and positions of sunspots vary in a cycle that lasts about
•
Sunspots initially appear in groups about midway between the sun’s
.
and
. The number of sunspots increases over the next few years until it reaches a peak of
100 of more sunspots.
•
After the peak, the number of sunspots begins to
until it reaches a minimum.
Solar Eruptions
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Other solar activities are affected by the sunspot cycle, such as the solar-activity cycle.
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The solar-activity cycle is caused by the changing solar
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This cycle is characterized by increases and decreases in various types of solar activity, including solar eruptions.
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Solar eruptions are events in which the sun lifts substantial material above the
atomic or
particles.
•
Solar eruptions include
, solar flares, and
.
and emits
mass ejections.
Prominences
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prominence a
photosphere.
•
Each solar prominence follows the curved
magnetic polarity to a region of the opposite magnetic polarity.
of relatively cool, incandescent gas that extends above the
field lines from a region of one
Solar Flares
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solar flare an
release of energy that comes from the sun and that is associated with
magnetic disturbances on the sun’s surface
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Solar flares are the most violent of all
•
Solar flares release the
can lead to the formation of coronal loops.
•
Some particles from a solar flare escape into space. These particles increase the strength of the
.
stored in the strong magnetic fields of sunspots. This release
.
Coronal Mass Ejections
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coronal mass ejection coronal gas that is thrown into
•
As gusts of particles strike Earth’s
, or the space around Earth that contains a
magnetic field, the particles can generate a sudden disturbance to Earth’s magnetic field, called a
from the sun
.
•
Geomagnetic storms have been known to interfere with
communications,
, and even cause blackouts.
Auroras
•
aurora colored light produced by charged particles from the
and from the
magnetosphere that react with and excite the oxygen and nitrogen of Earth’s upper atmosphere; usually seen in
the sky near Earth’s
.
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Auroras are the result of the
•
Auroras are usually seen close to Earth’s magnetic poles because electrically charged
between the solar wind and Earth’s magnetosphere.
are guided toward earth’s magnetic poles by Earth’s magnetosphere.