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Temp increase of sun from photosphere to corona

  1. Jun 7, 2004 #1
    The photosphere is 4500 K
    The chromosphere is 10000 K
    The corona is 1,000,000 K

    The temperature increases as the distance from the core increases. This makes no sense to me.

    Any ideas?

  2. jcsd
  3. Jun 7, 2004 #2


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    Those temps are a bit off:
    -The photosphere is ~5700-5800 K.
    -The chromosphere is 10000 K to ~500,000 K, mean of ~100,000K.
    (and only about 2000-3000 Km thick)
    -The corona is 1 million K to >3 million K.

    The corona is hot because it is ionized with electrons removed from the atoms by radiation from the photosphere and chromosphere "below". The amount of energy provided to coronal material depends on the current state of solar activity, CME's and magnetic fluctuations. At very high temperatures, iron atoms can have 9 to 13 electrons ejected. Nine-times ionized iron is only produced at temperatures of 1.3 million K and 13-times ionized iron means the temperature gets up to 2.3 million K. During strong solar activity, the temperature can reach 3.6 million K from 14-times ionized calcium.
  4. Jun 7, 2004 #3
    Is the the ionization the result of the 2.3 million K or does the temp reach 2.3 million K b/c of the ionization energy.???

    Cause or Effect???

  5. Jun 8, 2004 #4
    ^^^^^^^^^^^^^^ :confused:
  6. Jun 8, 2004 #5


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    The chromosphere is hotter than the photosphere from (1) photosphere EM radiation (whole spectrum) (2) strong magnetic disturbances (fluctuations from the photosphere and below) and (3) acoustic excitation.

    Add all of this to the energy from CME's, which originate from the chromosphere, not photosphere, and the additave energy of all sources excites (ionizes) the elements already existing in the corona. Therefore, the coronal elements are "heated" by these sources causing the ionization. Otherwise, there would be no source of energy to cause the strong ionization of iron, calcium, etc.
  7. Jun 9, 2004 #6


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    For quite a long time the mechanism by which the corona is heated was very much a mystery. As Labguy said, there are several mechanisms now recognised. In developing a detailed understanding of the photosphere/chromosphere/corona, a good deal of pretty hairy physics was done, esp plasma physics. Perhaps a PF member can recommend a good review book or paper?
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