The sun is a star, the center of the solar system, a huge ball of incandescent plasma. By its type, our star belongs to yellow dwarfs. Its radius is 696,000 km, its mass is 2x10 to the 30th power of kg, and the temperature of the radiating layer (photosphere) is 5770 K.
The source of solar energy is nuclear processes in the center of the luminary, where the temperature exceeds 10 million K. There, hydrogen atoms are converted into helium atoms. This is a typical case of a thermonuclear reaction - the fusion of light nuclei at an ultrahigh temperature with the release of energy. Every second 4,000,000 tons of solar matter is converted into energy.
Then this energy is radiated from the interior to the outer layer. There it is distributed by convection - mixing of solar matter. It is the convective motion of the plasma that determines the existence of, for example, sunspots. Sunspots are areas of low (4500 K) temperature on the sun's surface, which is why they look several times darker than the rest of the photosphere.
The activity of plasma processes in the Sun changes periodically: sunspots, torches in the photosphere, prominences in the corona regularly appear in the atmosphere. This frequency is approximately 11 years. Many processes on Earth depend on the activity of the Sun: crops in agriculture, magnetic storms. The relationship between the state of human health and solar activity is noted.
To characterize the radiation of the Sun, the concept of the solar constant was introduced - the amount of radiant energy arriving in 1 minute per 1 sq. Cm of the area perpendicular to the sun's rays at a distance of 1 AU. outside the earth's atmosphere. Astronomical unit (AU) is the average distance from the Sun to the Earth. Our planet receives about 2x10 17 watts of solar radiant energy.
The atmosphere absorbs much of the sun's radiation. The earth's surface reaches about 1 kW / sq.m. It is this energy that is the driving force of all processes taking place on the globe. Its amount varies throughout the year and depends mainly on the tilt of the earth's axis, and, to a lesser extent, on the distance from our planet to the Sun.