Chromosphere

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Chromosphere

The chromosphere (literally, "color sphere") is a thin layer of the Sun

Sun

The Sun , a G V star, is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 98.6% of the Solar System's mass....
's atmosphere just above the photosphere

Photosphere

The photosphere of an astronomical object is the region from which externally received light originates. The term itself is derived from Ancient Greek roots, f???- f?t??/photos meaning "light" and sfa????/sphairos meaning "ball," in reference to the fact that it is a ball-shaped surface perceived to emit light....
, roughly 2,000 kilometers deep. The chromosphere is more visually transparent than the photosphere. The name comes from the fact that it has a reddish color, as the visual spectrum

Spectrum

A spectrum is a condition that is not limited to a specific set of values but can vary infinitely within a Continuum . The word saw its first scientific use within the field of optics to describe the rainbow of colors in visible light when separated using a triangular prism ; it has since been applied by analogy to many fields other than op...
of the chromosphere is dominated by the deep red H-alpha

H-alpha

In physics and astronomy, H-alpha, also written Ha, is a specific red visible emission line created by hydrogen with a wavelength of 6562.8 ?ngstr?m....
spectral line of hydrogen. The coloration may be seen directly with the naked eye only during a total solar eclipse

Solar eclipse

A solar eclipse occurs when the Moon passes between the Sun and the Earth so that the Sun is wholly or partially obscured. This can only happen during a new moon, when the Sun and Moon are in conjunction as seen from the Earth....
, where the chromosphere is briefly visible as a flash of color just as the visible edge of the photosphere disappears behind the Moon

Moon

The Moon is Earth's only natural satellite and the List of natural satellites by diameter satellite in the Solar System. The average centre-to-centre distance from the Earth to the Moon is km, about thirty times the diameter of the Earth....
.

For reasons not fully understood the temperature of the chromosphere is hotter than that of the photosphere.

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Encyclopedia

The chromosphere (literally, "color sphere") is a thin layer of the Sun

Sun

Photosphere

Spectrum

H-alpha

Solar eclipse

Moon

Kelvin

The kelvin is a Units of measurement of temperature and is one of the seven SI base units. The Kelvin scale is a Thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero ....
to 6400 K but the chromosphere is about 4500 K to as high as 20,000 K. One theory is that sonic turbulence is the source of this higher temperature.

Without special equipment the chromosphere cannot normally be seen due to its being washed out by the overwhelming brightness of the photosphere. It can be seen clearly through special narrow-band optical filters

Band-pass filter

A band-pass filter is a device that passes frequency within a certain range and rejects frequencies outside that range. An example of an analog circuitue electronic band-pass electronic filter is an RLC circuit ....
tuned to the H-alpha spectral line

Spectral line

A spectral line is a dark or bright line in an otherwise uniform and continuous optical spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies....
, and many observatories routinely observe the chromosphere using this technique, which displays filament

Solar prominence

A prominence is a large bright feature extending outward from the Sun's surface, often in a Coronal loops configuration. Prominences are anchored to the Sun's surface in the photosphere, and extend outwards into the Sun's corona....
s quite clearly. Filaments (and prominences, which are filaments viewed from the side) are the source of many coronal mass ejection

Coronal mass ejection

A coronal mass ejection is an ejection of material from the Sun corona, usually observed with a white-light coronagraph.The ejected material is a Plasma consisting primarily of electrons and protons , plus the entraining coronal magnetic field....
s and hence are important to prediction of space weather

Space weather

Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a Celestial body atmosphere, and deals with phenomena involving ambient Plasma , magnetic fields, radiation and other matter in space....
.

The most common solar feature within the chromosphere are spicule

Spicule (solar physics)

In solar physics, a spicule is a dynamic jet of about 500 km diameter on the Sun. It moves upwards at about 20 km/s from the photosphere. They were discovered in 1877 by Father Angelo Secchi of the Vatican Observatory in Rome....
s, long thin fingers of luminous gas which appear like the blades of a huge field of fiery grass

Poaceae

Poaceae or Gramineae is a family in the Class Liliopsida of the Magnoliophyta. Plants of this family are usually called grasses; the shrub- or tree-like plants in this family are called bamboo ....
growing upwards from the photosphere below. Spicules rise to the top of the chromosphere and then sink back down again over the course of about 10 minutes.

Another feature found in the chromosphere are fibrils, horizontal wisps of gas similar in extent to spicules but with about twice the duration.

Finally, solar prominence
Solar prominence

A prominence is a large bright feature extending outward from the Sun's surface, often in a Coronal loops configuration. Prominences are anchored to the Sun's surface in the photosphere, and extend outwards into the Sun's corona....
s rise up through the chromosphere from the photosphere, sometimes reaching altitudes of 150,000 kilometers. These gigantic plumes of gas are the most spectacular of solar phenomena, aside from the less frequent solar flare

Solar flare

A solar flare is a violent explosion in a star's atmosphere releasing as much energy as 6 × 1025 Joules. Solar flares affect all layers of the solar atmosphere , heating Plasma to tens of million Kelvin and accelerating electrons, protons and heavier ions to near the speed of light....
s.

Above the chromosphere of some stars there is a so-called transition region, where the temperature increases rapidly to the hot corona

Corona

A corona is a type of Plasma "celestial body's atmosphere" of the Sun or other celestial body, extending millions of kilometres into space, most easily seen during a total solar eclipse, but also observable in a coronagraph....
, which forms the outermost part of the atmosphere.

See the of the solar chromosphere (Eclipse of March 7, 1970).

Chromosphere

See also