The size of the solar corona changes continuously throughout the sunspot cycle. The corona actually extends throughout the entire solar system as a 'wind' of particles, however, the densist parts of the corona is usually seen not more than about 1-2 solar radii from the surface or about 690,000 to 1.5 million kilometers at the equator. Near the poles, it seems to be a bit flatter. The so-called 'inner corona' extends about 1/3 of the solar radius ( 230,000 kilometers) above the photosphere and has a spectrum which shows no absorption lines, and an outer corona above it in which spectral lines are present. The inner corona is produced by sun light from the photosphere scattering off of the ionized gases in the inner corona.