The helium radiation in prominences |
| |
| Authors: | N A Yakovkin M Yu Zeldina |
| |
| Institution: | (1) University Observatory, Kiev, U.S.S.R. |
| |
| Abstract: | It is shown that the emission of quiescent and loop prominences in the helium D3 line and in the 4686 Å line of He+ respectively, occurs at low temperatures, of the order of 7000 K.The ionization of neutral helium is produced by short-wave solar radiation, which is absorbed in the outer layers of filaments composing a prominence. The population of helium triplet levels in prominences is determined by recombinations and subsequent resonance scattering of photospheric radiation. Transitions from triplet to singlet levels caused by electron collisions considerably reduce the line brightness.Emission of ionized helium in the 4686 Å line arises in prominence surface layers as well. In quiescent prominences the emission is very faint and is due to recombination; the second ionization is caused by the far ultraviolet radiation.In flare-like events ionized helium emits due to charge-exchange collisions. The symmetrical resonance charge-exchange of  -particles is caused by helium ions in corpuscular streams which are probably generated in photospheric layers. Due to increased radiation losses the temperature of the prominence under the action of the stream is negligibly increased. With a stream density equal to 5 × 108 cm-3 and velocity 300 km/s the theoretical intensity of the 4686 He+ line is some hundreds of microängströms and agrees with observations of Goldberg-Rogozinskaya (1962, 1965) and others. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
