![]() "SUMER Observations Confirm the Dynamic Nature of the Quiet Solar Outer Atmosphere: The Internetwork Chromosphere". New eyes on the sun : a guide to satellite images and amateur observation. ![]() ^ a b de Grijs, Richard Kamath, Devika (15 November 2021).^ a b "SP-402 A New Sun: The Solar Results From Skylab".^ "Supergiant Atmosphere of Antares Revealed by Radio Telescopes"."Multiwavelength Studies of MHD Waves in the Solar Chromosphere". ^ Jess, D.B Morton, RJ Verth, G Fedun, V Grant, S.T.D Gigiozis, I.Ī spectroscopic measure of chromospheric activity on other stars is the Mount Wilson S-index. They are most prominent and magnetically active on lower- main sequence stars, on brown dwarfs of F and later spectral types, and on giant and subgiant stars. They look similar to granules commonly observed on the photosphere due to the heat convection.Ĭhromospheres are present on almost all luminous stars other than white dwarfs. Images taken in typical chromospheric lines show the presence of brighter cells, usually referred to as the network, while the surrounding darker regions are named internetwork. When the plasma temperature of these loops becomes coronal (above 1 MK), these features appear more stable and evolve over longer times. Foukal studied these cool loops in detail from the observations taken with the EUV spectrometer on Skylab in 1976. These cool-temperature loops show an intense variability: they appear and disappear in some UV lines in a time less than an hour, or they rapidly expand in 10–20 minutes. They are different from solar prominences because they are concentric arches with maximum temperature of the order 0.1 MK (too low to be considered coronal features). Plasma loops can be seen at the border of the solar disk in the chromosphere. A wavelength of 656.3 nm is in the red part of the spectrum, which causes the chromosphere to have a characteristic reddish colour. In particular, one of its strongest lines is the H α at a wavelength of 656.3 nm this line is emitted by a hydrogen atom whenever its electron makes a transition from the n=3 to the n=2 energy level. The chromosphere's spectrum is dominated by emission lines. Without special equipment, the chromosphere cannot normally be seen due to the overwhelming brightness of the photosphere. The colour hues are anywhere between pink and red. This makes the chromosphere normally invisible and it can be seen only during a total eclipse, where its reddish colour is revealed. The density of the chromosphere is 10 −4 times that of the underlying photosphere and 10 −8 times that of the Earth's atmosphere at sea level. The temperature initially decreases from the inner boundary at about 6000 K to a minimum of approximately 3800 K, but then increasing to upwards of 35,000 K at the outer boundary with the transition layer of the corona (see Stellar corona § Coronal heating problem). The density of the Sun's chromosphere decreases exponentially with distance from the center of the Sun by a factor of roughly 10 million, from about 2 ×10 −4 kg/m 3 at the chromosphere's inner boundary to under 1.6 ×10 −11 kg/m 3 at the outer boundary. The red color of the chromosphere could be seen during the solar eclipse of August 11, 1999. For example, the chromosphere of supergiant star Antares has been found to be about 2.5 times larger in thickness than the star's radius. On large stars, chromospheres sometimes make up a significant proportion of the entire star. Ĭhromospheres have also been observed on stars other than the Sun. Information about the chromosphere is primarily obtained by analysis of its emitted electromagnetic radiation. The chromosphere has a characteristic red color due to electromagnetic emissions in the H α spectral line. Hair-like jets of plasma, called spicules, rise from this homogeneous region and through the chromosphere, extending up to 10,000 km (6,200 mi) into the corona above. It possesses a homogeneous layer at the boundary with the photosphere. In the Sun's atmosphere, the chromosphere is roughly 3,000 to 5,000 kilometers (1,900 to 3,100 miles) in height, or slightly more than 1% of the Sun's radius at maximum thickness. The term usually refers to the Sun's chromosphere, but not exclusively. The chromosphere emits electromagnetic radiation in the H α spectral line, allowing for it to be viewed using special filters.Ī chromosphere ("sphere of color") is the second layer of a star's atmosphere, located above the photosphere and below the solar transition region and corona.
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