Related topics: sun

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Sounding rocket CLASP2 elucidates solar magnetic field

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Scientists discover volcanoes on Venus are still active

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4,000th comet discovered by solar observatory

On June 15, 2020, a citizen scientist spotted a never-before-seen comet in data from the Solar and Heliospheric Observatory, or SOHO—the 4,000th comet discovery in the spacecraft's 25-year history.

Method to study the "traces" of coronal mass ejections

Scientists at Skolkovo Institute of Science and Technology (skoltech), together with colleagues from the Karl-Franzens University of Graz and the Kanzelhoehe Observatory (Austria), have developed an automatic method for detecting ...

Astronomers unveil the magnetic field of the solar corona

While the world has been dealing with the coronavirus pandemic, researchers at the University of Hawaiʻi Institute for Astronomy (IfA) have been hard at work studying the solar corona, the outermost atmosphere of the sun ...

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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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