Caption: A model of the Sun's atmosphere: i.e., its structure.

Features:

1. The model is certainly somewhat out of date since it was made in 1979. But qualitatively and to a degree quantitatively, it should still be OK.

2. The horizontal axis is temperature (in kelvins) at the bottom and density (in g/cm**3) at the top. Both thermodynamic variables (AKA state functions) are plotted with logarithmic scales.

   Note the gram per cubic centimeter is the density natural unit for life as we know it since that depends on liquid water whose density is always close to 1 g/cm**3.

3. The vertical axis is height (in kilometers) measured from a zero-point set at the top of the solar photosphere layer.

   The scale is NOT a logarithmic scale.

4. The model shows, going outward, the interior (more exactly the convective zone), solar photosphere, chromosphere, transition region, and corona,

5. The absorption line spectrum of the Sun probably mainly forms in the lower chromosphere at ∼ 500 km above the solar photosphere where the temperature reaches a minimum of ∼ 4100 K. (see Wikipedia: Sun's atmosphere).

6. Spicules are jets in the chromosphere. They are a feature of Sun weather.

7. See also Sun keywords below (local link / general link: keywords_sun.html):

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