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 ...

The sun as you've never seen it before

Powerful flares, breathtaking views across the solar poles, and a curious solar "hedgehog" are among the haul of spectacular images, movies and data returned by Solar Orbiter from its first close approach to the sun. Although ...

Countdown begins for the great North American solar eclipse

One year from now, on Monday, 8 April 2024, the moon will pass directly between Earth and the sun, creating a total solar eclipse like the one that crossed the United States from coast to coast on 21 August 2017. As it did ...

Scientists discover volcanoes on Venus are still active

A new study identified 37 recently active volcanic structures on Venus. The study provides some of the best evidence yet that Venus is still a geologically active planet. A research paper on the work, which was conducted ...

Mystery of coronae around supermassive black holes deepens

Researchers from RIKEN and JAXA have used observations from the ALMA radio observatory located in northern Chile and managed by an international consortium including the National Astronomical Observatory of Japan (NAOJ) to ...

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 ...

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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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