|
The chromosphere (literally, "sphere of color") is the second of the three main layers in the Sun's atmosphere and is roughly 2,000 kilometers deep. It sits just above the photosphere and just below the solar transition region. The density of the chromosphere is very low, it being only 10−4 times that of the photosphere, the layer just below it, and 10−8 times that of the atmosphere of Earth. This makes the chromosphere normally invisible and it can be seen only during a total eclipse, where its reddish color is revealed. The color hues are anywhere between pink and red.〔 〕 However, without special equipment, the chromosphere cannot normally be seen due to the overwhelming brightness of the photosphere. The density of the chromosphere decreases with distance from the center of the sun. This decreases logarithmically from 1017 particles per cubic centimeter, or approximately to under at the outer boundary.〔 〕 The temperature begins to decrease from the inner boundary of about 6,000 K〔 (【引用サイトリンク】 title=SP-402 A New Sun: The Solar Results From Skylab )〕 to a minimum of approximately 3,800 K, before increasing to upwards of 35,000 K〔 at the outer boundary with the transition layer of the corona. Figure 1 shows the trends which density and temperature follow through the chromosphere. Chromospheres have been observed also for stars different from the Sun.〔 〕 ==Comparing chromosphere and photosphere== Whilst the photosphere has an absorption line spectrum, the chromosphere's spectrum is dominated by emission lines. 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. A wavelength of 656.3 nm is in the red part of the spectrum, which causes the chromosphere to have its characteristic reddish colour. By analysing the spectrum of the chromosphere, it was found that the temperature of this layer of the solar atmosphere increases with increasing height in the chromosphere itself. The temperature at the top of photosphere is only about 4,400 K, while at the top of chromosphere, some 2,000 km higher, it reaches 25,000 K.〔〔 〕 This is however the opposite of what we find in the photosphere, where the temperature drops with increasing height. It is not yet fully understood what phenomenon causes the temperature of the chromosphere to paradoxically increase further from the Sun's interior. However, it seems likely to be explained, partially or totally, by magnetic reconnection. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「chromosphere」の詳細全文を読む スポンサード リンク
|
