Related topics: sun

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The GRAPES-3 muon telescope, the largest and most sensitive cosmic ray monitor recorded a burst of galactic cosmic rays that indicated a crack in the Earth's magnetic shield. The burst occurred when a giant cloud of plasma ...

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(PhysOrg.com) -- A missing jet stream, fading spots, and slower activity near the poles say that our Sun is heading for a rest period even as it is acting up for the first time in years, according to scientists at the National ...

Mystery of coronae around supermassive black holes deepens

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Chasing the Total Solar Eclipse from NASA's WB-57F jets

For most viewers, the Aug. 21, 2017, total solar eclipse will last less than two and half minutes. But for one team of NASA-funded scientists, the eclipse will last over seven minutes. Their secret? Following the shadow of ...

Eclipse science along the path of totality

Leading U.S. solar scientists today highlighted research activities that will take place across the country during next month's rare solar eclipse, advancing our knowledge of the Sun's complex and mysterious magnetic field ...

New clue to solving the mystery of the Sun's hot atmosphere

The elemental composition of the Sun's hot atmosphere known as the 'corona' is strongly linked to the 11-year solar magnetic activity cycle, a team of scientists from UCL, George Mason University and Naval Research Laboratory ...

Experts discover heavenly solar music (w/ Video)

Musical sounds created by longitudinal vibrations within the Sun's atmosphere, have been recorded and accurately studied for the first time by experts at the University of Sheffield, shedding light on the Sun's magnetic atmosphere.

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Corona

A corona is a type of plasma "atmosphere" of the Sun or other celestial body, extending millions of kilometers into space, most easily seen during a total solar eclipse, but also observable in a coronagraph. The Latin root of the word corona means crown.

The high temperature of the corona gives it unusual spectral features, which led some to suggest, in the 19th century, that it contained a previously unknown element, "coronium". These spectral features have since been traced to highly ionized iron (Fe-XIV) which indicates a plasma temperature in excess of 106 kelvin. The fact that the Sun has a million degree corona was first discovered by Gotrian in 1939 and Bengt Edlén in 1941 by identifying the coronal lines (observed since 1869) as transitions from low lying metastable levels of the ground configuration of highly ionized metals (the green FeXIV line at 5303 Å, but also the red line FeX at 6374 Å).

Light from the corona comes from three primary sources, which are called by different names although all of them share the same volume of space. The K-corona (K for kontinuierlich, "continuous" in German) is created by sunlight scattering off free electrons; Doppler broadening of the reflected photospheric absorption lines completely obscures them, giving the spectral appearance of a continuum with no absorption lines. The F-corona (F for Fraunhofer) is created by sunlight bouncing off dust particles, and is observable because its light contains the Fraunhofer absorption lines that are seen in raw sunlight; the F-corona extends to very high elongation angles from the Sun, where it is called the Zodiacal light. The E-corona (E for emission) is due to spectral emission lines produced by ions that are present in the coronal plasma; it may be observed in broad or forbidden or hot spectral emission lines and is the main source of information about the corona's composition.

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