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					The Sun


          1
            Guiding Questions

1. Does the Sun have a solid surface?
2. Since the Sun is so bright, how is it
   possible to see its dim outer
   atmosphere?
3. Where does the solar wind come from?
4. What are sunspots? Why do they appear
   dark?
5. What is the connection between
   sunspots and the Sun’s magnetic field?
6. What causes eruptions in the Sun’s
   atmosphere?                            2
Introduction
Table 13-1




               3
Photosphere
The photosphere is the lowest of three main layers
           in the Sun’s atmosphere
Fig. 13-1: The Photosphere
                             • The Sun’s atmosphere
                               has three main layers: the
                               photosphere, the
                               chromosphere, and the
                               corona
                             • Everything below the
                               solar atmosphere is
                               called the solar interior
                             • The visible surface of the
                               Sun, the photosphere, is
                               the lowest layer in the
                                                          4
                               solar atmosphere
Convection in the photosphere produces granules
         Fig. 13-3: Granules




                                            5
                           6
Fig. 13-4: Supergranules
  Chromosphere
   The chromosphere is characterized by spikes
                 of rising gas
                         Fig. 13-5: Chromosphere
• Above the
  photosphere is a
  layer of less dense
  but higher
  temperature gases
  called the
  chromosphere
• Spicules extend
  upward from the
  photosphere into the
  chromosphere along
  the boundaries of
  supergranules                                    7
                                  8
Fig. 13-6: The Solar Atmosphere
  Corona
The corona ejects mass into space to form the solar wind
                Fig. 13-8: The Solar Corona




                                                     9
Activity in the corona includes coronal mass ejections and coronal holes
                    Fig. 13-9: The Ultraviolet Corona




                                                                   10
Sunspots
Sunspots are low-temperature regions in
           the photosphere
          Fig. 13-10: The Sunspots




                                          11
Fig. 13-11: The Sun’s
Rotation with Sunspots




                         12
Fig. 13-12: Sunspot Maximum and Minimum
                                          13
Sunspots are produced by a 22-year cycle
      in the Sun’s magnetic field
         Fig. 13-13: The Sunspot Cycle




                                           14
     Fig. 13-14: Variations in the Average Latitude of Sunspots
• The Sun’s surface features vary in an 11-year cycle
• This is related to a 22-year cycle in which the surface magnetic field
  increases, decreases, and then increases again with the opposite polarity
• The average number of sunspots increases and decreases in a regular cycle
  of approximately 11 years, with reversed magnetic polarities from one 11-
  year cycle to the next
• Two such cycles make up the 22-year solar cycle                        15
Sun’s Magnetic Fields




       Fig. 13-15: Mapping the Sun’s Magnetic Field

The magnetic-dynamo model suggests that many
features of the solar cycle are due to changes in
the Sun’s magnetic field
                                                      16
Fig. 13-16: Sunspots and Magnetic Fields
                                           17
Fig. 13-18: Rotation of the Solar Interior




                                             18
   Other Magnetic Activities
    The Sun’s magnetic field also produces other
               forms of solar activity

• Solar Flares: A solar
  flare is a brief
  eruption of hot,
  ionized gases from a
  sunspot group
• Coronal Mass
  Ejection: A coronal
  mass ejection is a
  much larger eruption
  that involves
  immense amounts of
  gas from the corona     Fig. 13-19: Magnetic Arches in the Corona
                                                                 19
Prominences, Filaments, Plages




        Fig. 13-20a: Prominences, etc - I.   20
Fig. 13-20b: Prominences, etc - II.   21
Fig. 13-21: Coronal Mass Ejection   22
Internal
Solar
Layers



           23
              Nuclear Fusion !

• At 15 million degrees Celsius in the center
  of the star, fusion ignites !
• 4 (1H) --> 4He + 2 e+ + 2 neutrinos +
  energy
   • Where does the energy come from ?
    • Mass of four 1H > Mass of one 4He
                           E = mc2


                                            24
               A Balancing Act

• Energy released from nuclear fusion
  counter-acts inward force of gravity.

Throughout its life, these
two forces determine the
stages of a star’s life.



                                          25
                    Key Words
•   22-year solar cycle • Fusion
•   chromosphere         • granule
•   conduction           • photosphere
•   Convection           • plasma
•   Convection zone
                         • Prominence
•   core
                         • Radiation zone
•   corona

                                            26

				
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posted:11/10/2011
language:English
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