The internal structure of the Sun is defined under the assumption that it is spherically symmetric body and is in equilibrium. Energy transport equation, the energy conservation law equation of state of ideal gas, Stefan-Boltzmann law and the conditions of hydrostatic, radiative and convective equilibrium with the values determined from observations of total luminosity, total mass and radius of the Sun and the data on its chemical composition make it possible to construct a model the internal structure of the Sun.
The internal structure of the Sun is defined under the assumption that it is spherically symmetric body and is in equilibrium. Energy transport equation, the energy conservation law equation of state of ideal gas, Stefan-Boltzmann law and the conditions of hydrostatic, radiative and convective equilibrium with the values determined from observations of total luminosity, total mass and radius of the Sun and the data on its chemical composition make it possible to construct a model the internal structure of the Sun. It is believed that the hydrogen content in the Sun by weight about 70% of helium is about 27%, the content of all other elements of about 2.5%. Based on these assumptions, calculated that the temperature at the center of the Sun is 10-15o1056 K, a density of about 1,5 o1055 kg / m, the pressure of 3,4 o10516 n / m (about 3o10511 atmospheres). It is believed that the source of energy augmentation loss by radiation and maintaining the heat of the Sun, are nuclear reactions occurring in the solar interior. The average amount of energy produced inside the Sun is 1.92 erg / g / sec. The energy release is determined by nuclear reactions in which hydrogen is converted into helium. On the Sun may be two groups of fusion reactions: the so-called proton-proton (hydrogen) cycle and the carbon cycle (cycle Bethe). Most likely that the Sun dominates the proton-proton cycle, consisting of three reactions, the first of which from the hydrogen nuclei are formed the nucleus of deuterium (a heavy isotope of hydrogen, atomic mass, the second of the hydrogen nuclei are formed the nucleus of the isotope of helium with atomic mass 3 and Finally, a third of them formed the nucleus stable isotope of helium with Atomic mass 4.
Energy transfer from the internal layers of the sun occurs mainly through the absorption of electromagnetic radiation coming from below, and subsequent re-emission. As a result of temperature decrease with distance from the Sun is gradually increasing wavelength, carries most of the energy in the upper layers. Energy transfer movement of hot material from the inner layers, and cooled inside the (convection) plays an essential role in the relatively higher layers, forming the solar convection zone, which begins at a depth of about 0.2 solar radii and has a thickness of about 1,058 m. Velocity of convective motions increases with distance from the center of the sun and in the outer convective zone reaches (2-2,5) h1053 m / sec. In a still higher layers (in the solar atmosphere) the transfer of energy again by radiation. In the upper atmosphere of the Sun (the chromosphere and the corona) of the energy delivered to the mechanical and magnetohydrodynamic waves are generated in the convection zone, but are absorbed only in these layers. Density in the upper atmosphere is very small, and the necessary removal of energy by radiation and heat conduction is only possible if the kinetic energy of these layers is large enough. Finally, at the top of the solar corona, most of the energy carried away streams of matter moving from the sun, called solar wind. The temperature in each layer is set at a level that is automatically energy balance: the number brought by the energy due to absorption of all types of radiation, heat conduction, or movement of matter is equal to the sum of all the energy losses of the layer.
Full solar radiation is determined by the light produced by them on the surface of the Earth – about 100 thousand lux, when the sun is at its zenith. Outside the atmosphere at an average distance of Earth from the sun light is 127,000 lux. The light intensity of the sun is 2,84 o10527 candles. The amount of energy coming in one minute on an area of 1 cm, as set perpendicular to the sun’s rays outside the atmosphere at an average distance of Earth from the sun, called solar constant. Total capacity of solar radiation – 3,83 o10526 watts, of which the Earth goes around 2o10517 watts, the average brightness of the sun’s surface (under the supervision outside the Earth’s atmosphere) is 1,98 o1059 nt, the brightness center of the disk of the Sun – 2,48 o1059 nt. The brightness of the solar disk decreases from center to edge, and this decrease depends on the wavelength, so that the brightness at the edge of the solar disk for light with a wavelength of 3600A is 0,2 luminance of its center, and for the 5000A – about 0.3 brightness center of the disk of the Sun . At the very edge of the solar disk brightness decreases by 100 times for less than one second of arc, so the boundary of the solar disk looks very sharp.
Spectral composition of light emitted by the Sun, ie the distribution of energy in the center of the Sun, roughly corresponds to the distribution of energy in a blackbody radiation with a temperature of about 6000 K. However, in some parts of the spectrum there are significant deviations. The maximum energy in the solar spectrum corresponds to a wavelength of 4600 A. Solar spectrum – a continuous spectrum, which imposed no more than 20 thousand absorption lines. More than 60% of them identified with spectral lines of known chemical elements by comparing the wavelengths and relative intensity of the absorption lines in the solar spectrum with laboratory spectra. The study of absorption lines provides information not only on the chemical composition of the solar atmosphere, but also about physical conditions in those layers, which produce certain absorption. Predominant element in the Sun is hydrogen. Number of helium atoms is 4-5 times smaller than hydrogen. The number of atoms of all other elements combined, at least 1000 times less than the number of hydrogen atoms. Among them are most abundant oxygen, carbon, nitrogen, magnesium, iron and others. In the solar spectrum can be identified as lines belonging to certain molecules and free radicals: OH, NH, CH, CO and others. Magnetic fields on the Sun are measured mainly by the Zeeman splitting of absorption lines in the solar spectrum. There are several types of solar magnetic fields. Total magnetic field of the sun is low and reaches a strength of 1 of this or another polarity and varies with time. This field is closely related to the interplanetary magnetic field and its sectoral structure. Magnetic fields associated with solar activity, can reach in sunspots tension in several thousand. The structure of magnetic fields in active regions is very complicated, alternating magnetic poles of different polarity. There are also local magnetic field with the field in the hundreds outside of sunspots. Magnetic fields penetrate into the chromosphere and the solar corona. Large role in the Sun play magnetogasdynamic and plasma processes. At a temperature of 5000 – 10000 K ionized gas is enough, its conductivity is great and thanks to the huge scale solar phenomena significance of electromechanical and magnetomechanical interaction is very large.