Which sun layer extends within 100 miles of the sun's surface?

Answer 1

The photosphere generally defines the surface of a star having a convective envelope. I think it's defined as the first two-thirds of an optical depth, so the radius interval depends on the star's opacity, which is a function of effective temperature and composition.

Answer 2

It's not the caronasphere, as that extends much farther. It is most likely the chromosphere.

Answer 3

The corona