by Sergei YAZEV, Dr. Sc. (Phys. & Math.), Director of the Astronomic Observatory of the Irkutsk State University, senior researcher of the Institute of Solar-Terrestrial Physics, RAS Siberian Branch (Irkutsk) The year 2009 marked an outstanding event in the history of astronomy, i.e. the 400th anniversary of the first telescope-based observations of the starlit sky. The pioneers were Galileo Galilei in Italy, Johann Goldschmidt (Fabricius) in Holland, Thomas Harriot in England and Christoph Scheiner in Germany. Owing to optical devices back in early 17th century, it was managed to discover black spots on the Sun and confirm that the formations on the Sun and not planets in their orbital motion happened to be on the Sun-Earth line. Long after it has been found that such spots are concerned at least with three levels of the solar activity organization. One of them has become a subject of our discussion. SPOTS AND ACTIVE LONGITUDES During a period of four centuries scientists studied in detail the phenomenon of solar spots. In early 20th century the American astronomer George Ellery Hale made two notable discoveries in regard of these grandiose formations according to terrestrial standards. First, spectral observations have proved that the temperature in the spots is less than in the surrounding photosphere (visible radiating surface layer) of the Sun, and the difference makes 1,000-1,500 K and more. Secondly, the spots have strong magnetic fields, which are actually their basis. By hindering convection (heat transfer by rising plasma fluxes) the magnetic fields result in a decrease of energy exit from the star depths and, correspondingly, to a temperature decrease and relative reduction of brightness of these formations. The large spots reveal a central and darkest part or "a shadow" surrounded by a lighter circular area or "a penubra". стр. 4 The magnetic fields are mainly vertical in shadows and quasi-horizontal in penubras. ... Читать далее