The Sun EIT (Extreme ultraviolet Imaging Telescope) images the solar atmosphere at several wavelengths, and therefore, shows solar material at different temperatures. In the images taken at 304 Angstroms the bright material is at 60,000 to 80,000 degrees Kelvin. In those taken at 171, at 1 million degrees. 195 Angstrom images correspond to about 1.5 million Kelvin. 284 Angstrom, to 2 million degrees. The hotter the temperature, the higher you look in the solar atmosphere. A "typical" star. Photosphere Visible portion of the Sun, only about 500 km thick. About 6000 K. Texas-sized granulation ? FUDGE. Oscillations. Chromosphere Extends 10,000 km above photosphere. Briefly visible (pinkish) during total solar eclipse. Corona Extends at least 30 solar radii into space. Very HOT ? 1,000,000 K ? but very low density. Is due to interaction between magnetic fields and the rotation of the Sun. The outer corona is continuously leaving the Sun as the SOLAR WIND ? blows past the Earth at 300 to 400 km/sec. Sunspots. A relatively cool, hence dark, area of the surface. Average spot is twice the diameter of the Earth, and lasts a week or so. Almost always form in pairs, or even larger groups. Associated with strong magnetic fields. Differential rotation of the Sun thought to cause the bipolar sunspot pair. Sunspot Cycle. Activity varies with an 11 year period ? complete cycle has a 22 year period. The Maunder Butterfly. Prominences ? ionized gases trapped in twisted magnetic fields over areas of sunspot activity ? can last for months. Flares. The so-called solar tsunami rolls across the Sun after being kicked up by a major flare on Dec. 6, 2006. (Credit: NSO/AURA/NSF and USAF Research Laboratory via Spaceweather.com) MUCH larger, more violent that prominences. Emit X-rays, UV, visible, and also high energy protons and electrons. Also linked to magnetic phenomena. Affect communications on Earth and cause the Aurora Borealis. In a recent survey of 1,120 American adults, almost half did not know that the sun is a star. This is worse than it seems; they were given hints. When asked "Would you say that the sun is a planet, a star, or something else?" 55% said a star; 25% said a planet; 15% something else; and 5% either did not know or refused to answer. In a seperate survey, it has been reported that 5% of people are intoxicated at any given time. Coincidence? On the left, a sunspot group seen at visible wavelengths. On the right, a photograph made in the far ultraviolet detects the hot gas trapped in the magnetic fields arching above the sunspot group. Note the resemblance in shape to the magnetic field around an ordinary bar magnet.
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