Section 2: Solar Activity

1. Section 2: Solar Activity Preview • Objectives • Sunspots • The Sunspot Cycle • Solar Ejections • Auroras • Maps in Action

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.

3. 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 *.

4. 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.

5. 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.

6. Sunspots

7. 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.

8. 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.

9. 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.

10. 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.

11. 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.

12. Maps in Action SXT Composite Image of the Sun