Question

As the moon covers the solar disk during a solar eclipse, a flash spectrum of the sun's chromosphere can be recorded. This flash spectrum reveals an emission spectrum and provides information on the properties of the chromosphere. As the moon moves from the inner chromosphere to the outer chromosphere, the spectral lines present in the flash spectrum change. What is going on in the chromosphere that produces the changes in the flash spectrum?

Answer 1

The answer is:

the change observable in the flash spectrum occurs because, as the moon moves out of the inner part of the chromosphere, the temperature of the chromosphere increases as the distance between the moon and the photosphere decreases; the direct opposite happens to the chromosphere density, which also decreases.

All of this causing observable changes in the light of the spectrum.