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The Sun
Section 2: Solar Activity
Preview
• Objectives
• Sunspots
• The Sunspot Cycle
• Solar Ejections
• Auroras
• Maps in Action
Section 2
The Sun
Section 2
Objectives
• Explain how sunspots are related to powerful magnetic
fields on the sun.
• Compare prominences, solar flares, and coronal mass
ejections.
• Describe how the solar wind can cause auroras on
Earth.
The Sun
Section 2
Sunspots
• Sunspot *
• The movements of gases within the sun’s convective
zone and the movements caused by the sun’s rotation
produce magnetic fields.
• These magnetic fields cause *.
The Sun
Section 2
Sunspots
• Slower convection causes a decrease in the amount of
gas that is transferring energy from the core of the sun to
these regions of the photosphere.
• 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 darker than their surrounding regions.
• * are called sunspots.
The Sun
Section 2
The Sunspot Cycle
• Observations of sunspots have shown that the sun
rotates.
• The numbers and positions of sunspots vary in a cycle
that lasts about 11 years.
• Sunspots initially appear in groups about midway
between the sun’s equator and poles. The number of
sunspots increases over the next few until it reaches a
peak of 100 of more sunspots.
• After the peak, the number of sunspots begins to
decrease until it reaches a minimum.
The Sun
Sunspots
Section 2
The Sun
Section 2
Solar Ejections
• Other solar activities are affected by the sunspot cycle,
such as the solar-activity cycle.
• The solar-activity cycle is caused *.
• This cycle is characterized *.
• Solar ejections are events in which the sun emits atomic
particles.
The Sun
Section 2
Solar Ejections, continued
Prominences
• prominence *
• Solar ejections include prominences, solar flares, and
coronal mass ejections.
• Prominences are huge arches of glowing gases that
follow the curved lines of the magnetic force from a
region of one magnetic force to a region of the opposite
magnetic polarity.
The Sun
Section 2
Solar Ejections, continued
Solar Flares
• solar flare *
• Solar flares are the most violent of all solar disturbances.
• Solar flares release the energy stored in the strong
magnetic fields of sunspots. This release can lead to the
formation of coronal loops.
The Sun
Section 2
Solar Ejections, continued
Coronal Mass Ejections
• coronal mass ejection *
• Some of the particles from a solar flare escape into
space, increasing the strength of the solar wind.
• Particles also escape as coronal mass ejections. The
particles in the ejection can cause disturbances to
Earth’s magnetic field.
• These disturbances have been known to interfere with
radio communications, satellites, and even cause
blackouts.
The Sun
Section 2
Auroras
• aurora *
• Auroras are the result of the interaction between the
solar wind and Earth’s magnetosphere.
• Auroras are usually seen close to Earth’s magnetic poles
because electrically charged particles are guided toward
earth’s magnetic poles by Earth’s magnetosphere.
The Sun
Maps in Action
SXT Composite Image of the Sun
Section 2