EARTH & SPACE SCIENCE

1. EARTH & SPACE SCIENCE Chapter 29 The Sun 29.2 Solar Activity

2. 29.2 Solar Activity 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. Introduction The gases that make up the sun’s interior and atmosphere are in constant motion. The sun also rotates on its axis. Places close to the equator on the sun’s surface take 25.3 Earth days to rotate once. Places near the poles of the sun take 33 Earth days to rotate once.

4. Sunspots A sunspot is a dark area of the photosphere of the sun that is cooler than the surrounding areas and that has a strong magnetic field. 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 convection to slow in parts of the convective zone.

5. 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. These, cooler, darker areas are called sunspots.

6. http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question17.htmlhttp://starchild.gsfc.nasa.gov/docs/StarChild/questions/question17.html http://sohowww.nascom.nasa.gov/gallery/posters.html

7. 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 years 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.

8. Sunspots Video Links Powerful sun / our Solar System / 11 year Sunspot cycle 22 year Solar cycle / Solar cycle 24 (3:26) - http://youtu.be/ei7MBRaoVu4 The Solar Cycle* *(Same as above link, but more clear) (3:26) - http://youtu.be/AcAoHXOrqL8 NASA - Solar activity by SOHO space capsule (5:50) - http://youtu.be/Y012FYE8G3k

9. Solar Ejections Other solar activities are affected by the sunspot cycle, such as the solar-activity cycle. The solar-activity cycle is caused by the changing solar magnetic field. This cycle is characterized by increases and decreases in various types of solar activity, including solar ejections. Solar ejections are events in which the sun emits atomic particles.

10. Solar Ejections A prominence is a loop of relatively cool, incandescent gas that extends above the photosphere. 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.

11. Solar Ejections Video Links NASA - Magnificent Eruption in Full HD 1080p (2:11) - http://youtu.be/orqeYbqSiLg A prominence eruption observed by AIA (:10) - http://youtu.be/Lmm3J0WAres Extreme Solar Flares (2:53) - http://youtu.be/nmDZhQAIeXM NASA SDO - Summer Solstice Coronal Mass Ejection (0:35) - http://youtu.be/rqtOUqwQVFY

12. Solar Ejections A solar flare is an explosive release of energy that comes from the sun and that is associated with magnetic disturbances on the sun’s surface 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.

13. Solar Ejections A coronal mass ejection is a part of coronal gas that is thrown into space from the sun. 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.

14. http://www.nasa.gov/mission_pages/rbsp/science/rbsp-spaceweather.htmlhttp://www.nasa.gov/mission_pages/rbsp/science/rbsp-spaceweather.html

15. Coronal Mass Ejection Solar Prominence Captured by NASA’s Solar Dynamics Observatory http://sec.gsfc.nasa.gov/Roadmap_graphics.htm http://www.flickr.com/photos/lightsinthedark/5821379923/

16. http://www.nasa.gov/mission_pages/sunearth/news/News041612-M1.7flare.htmlhttp://www.nasa.gov/mission_pages/sunearth/news/News041612-M1.7flare.html

17. Auroras An aurora is a colored light produced by charged particles from the solar wind 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 magnetic poles. 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.

18. http://www.geo.mtu.edu/weather/aurora/images/aurora/jan.curtis/http://www.geo.mtu.edu/weather/aurora/images/aurora/jan.curtis/

19. Auroras Video Links NASA | The Mystery of the Aurora (2:15) - http://youtu.be/PaSFAbATPvk NASA. Aurora Borealis over Canada (1:02) - http://youtu.be/knInAjlZRec