Solar Structure: Structures & Vocabulary

The Sun is a self-gravitating sphere of hot plasma organized into layers defined by how energy is generated, transported, and emitted. Its interior consists of the core, radiative zone, and convective zone, while its atmosphere includes the photosphere, chromosphere, transition region, and corona.

Gravity compresses the solar interior while gas and radiation pressure resist collapse, producing hydrostatic equilibrium. In the radiative zone photons exchange energy repeatedly with matter, while in the convective zone bulk plasma motions carry energy outward. Temperature, density, pressure, and ionization change strongly with radius.

Solar models are constrained by the Sun's mass, radius, luminosity, composition, spectrum, and age. Helioseismology probes internal sound-speed structure, while spectroscopy identifies atmospheric composition and temperature. Imaging at different wavelengths isolates features in the photosphere, chromosphere, and corona.

From center outward, solar structure includes core, radiative zone, tachocline, convective zone, photosphere, chromosphere, transition region, and corona. Temperature falls outward through most of the interior but rises dramatically again in the outer atmosphere. Density changes by many orders of magnitude between the core and corona.