The Sun's Radiation

The end product of the sun's violent thermonuclear reactions is energy emitted over the complete spectrum of electromagnetic radiation. The electromagnetic spectrum consists of radiation of all known wavelengths, including those of visible light as well as those too long or too short to be seen by the human eye.

In order of increasingly longer wavelengths, the sun's radiation includes gamma rays, X rays, and ultraviolet light; next are visible light and infrared light, followed by a wide range of radio waves.

The sun also gives off radiation in another form. Because the corona, or outer atmosphere, is unstable, streams of charged particles are constantly pushed out by the sun in what is called the solar wind. The higher-energy particles in the solar wind are sometimes known as solar cosmic rays.

The earth's atmosphere acts as a shield to block out certain wavelengths of radiation harmful to life, particularly cosmic rays, X rays, and nearly all ultraviolet light. Of the radiation that penetrates the atmosphere, most is visible light, or sunlight, and infrared light, which produces heat in objects it strikes. The small amount of ultraviolet light that passes through the upper atmosphere aids the human body in producing vitamin D and is also responsible for causing suntan and sunburn.

Certain short radio waves emitted by the sun also pass through the atmosphere, but longer radio waves are reflected back into space. Radiation and particles emitted from large solar flares and those carried by the solar wind sometimes create strong disturbances in the earth's magnetic field. The auroras commonly seen in polar latitudes result when charged solar particles react with atoms of the upper atmosphere.