Interesting Facts about Our Sun

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Slide 23

The Transition Zone

h ~ 2300 – 2600 km above photosphere

Transition from moderate to high ionization

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T ~ 25,000 → 106 K

n ~ 107 → 105 cm-3

Observe selective heights in (UV) emission lines of ionized metals

Ly a → ~ 20,000 K

CIII 977 → ~ 90,000 K

O VI 1032 → ~ 300,000 K

Mg X 625 → ~ 1,400,000 K

Slide 24

The Solar Corona

Very hot (T ≥ 106 K), low-density (n ≤ 105 cm-3) gas

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Slide 25

Active vs. Quiescent Corona

Near Solar Maximum

Near Solar Minimum

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Slide 26

Coronal Holes

X-ray images of the sun reveal coronal holes.

These arise at the foot points of open field lines and are the origin of the solar wind.

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