Which layer of the sun's atmosphere is visible during a total solar eclipse?

During a total solar eclipse, the layer of the sun's atmosphere that becomes visible is the chromosphere. This layer lies above the photosphere and below the corona. The chromosphere can be observed as a thin, reddish ring of light during the brief moments when the moon completely covers the sun's bright disk. The light from the chromosphere is emitted in the red part of the spectrum due to the presence of hydrogen atoms, which is characteristic of this layer.

While the photosphere is the visible surface of the sun and is typically what we see under normal conditions, during an eclipse, it is obscured, allowing the chromosphere's unique features to become prominent. The corona, which is the outermost layer of the sun's atmosphere, can also be seen during an eclipse, but it appears as a more diffuse halo surrounding the sun rather than the pronounced colors seen in the chromosphere. The core, being the innermost layer where nuclear fusion occurs, is not visible during an eclipse.

Thus, identifying the chromosphere as the visible layer during a total solar eclipse highlights its importance and distinguishes it from the other atmospheric layers of the sun.