1. Chapter 7 The Sun

2. Solar Prominence – photo by SOHO spacecraft from the Astronomy Picture of the Day site link

3. The atmosphere of the Sun The outer layers are all parts of the Sun’s atmosphere: Corona Transition zone Chromosphere The Photosphere is the “surface” of the Sun; it emits the light that we see. The Convection and Radiation Zones are named for how energy is transported in the interior of the Sun.

4. Solar Granulation in the photosphere can be seen in movies taken by the SOHO cameras This granulation shows that convection is occurring under the surface of the Sun. On average these granules are about the size of a large state like Texas (up to 1000 miles across).

5. Above the granular photosphere is the chromosphere.

6. Solar spicules are relatively cool and hence dark features that appear above the chromosphere. These spicules are jets of gas that rise up above the chromosphere.

7. Absorption of various wavelength of light occurs in the solar chromosphere This region is usually only visible to us during a total solar eclipse. Also visible in this photo are prominences.

8. Next are the transition zone and the Solar Corona

9. The Solar Corona is most obvious during a total solar eclipse.

10. Solar Atmospheric Temperature So much energy is flowing through this region and the density is so low that the temperature of these regions is very high. All of this energy causes gas to “boil” off into space, or causes gas to be “pushed” off the surface of the Sun. This gas is called the Solar Wind.

11. Solar Spectrum This absorption spectra tells us what elements are in the Sun’s chromosphere and most likely in the rest of the Sun, except in the core.

12. Sunspots, Up Close Sunspots are also regions of intense magnetic fields. Just like regular magnets, sunspots come in pairs one is a “North pole” and one is a “South pole” Dark region – umbra (4300 K) Brighter region – penumbra (5000 K) Granules – (5800 K)

13. Sunspots behave somewhat like a magnet, causing a magnetic field above the photosphere.

14. Above the sunspot, the magnet field causes the hot gas of the corona to concentrate along the field lines, seen here is a photo in the ultraviolet.

16. Solar Rotation The Sun has Differential rotation which means different parts of the Sun rotate at different speeds. The Sun’s equator rotates faster than at the poles.

17. Solar Rotation “drags” the magnetic field around. All of the sunspot pairs in the north hemisphere have the same polarity or orientation. All of the sunspot pairs in the southern hemisphere have the opposite polarity.

18. Sunspot Cycle Both the number and the location of the sunspots change during the Sunspot or Solar Cycle which lasts 11 years

19. The “active Sun” refers to times when there are lots of sunspots and the surface of the Sun is very active in other ways. Many Prominences, Flares, and Coronal Mass Ejections can be seen. Also during this time the corona becomes larger and more irregularly shaped

20. Solar Prominences are loops of hot gas that rise from the surface of the sun. They are shaped by the magnetic fields of the Sun. Link: http://sohowww.nascom.nasa.gov/ http://sohowww.nascom.nasa.gov/

21. Solar Flares are much more rapid than prominences.

22. Solar Flare A rapidly expanding "solar quake" on the Sun’s surface depicted here by the Michelson Doppler Imager (MDI). It immediately followed a solar flare on 1996 July 6 and spread out more than 100,000 km at the solar surface. Scientists have shown that solar flares produce seismic waves, and gigantic seismic quakes, in the Sun's interior. They have tracked these seismic waves and found that "sun-quakes" closely resemble earthquakes on our planet. http://sohowww.nascom.nasa.gov/

23. Coronal Mass Ejection Coronal Mass Ejection events (CME) is when an eruption on the surface of the Sun ejects large amounts of gas into space. These events are larger than solar flares and are less frequent.