Showing papers on "Solar transition region published in 1979"
TL;DR: In this article, the authors present evidence for continuum absorption in the solar transition zone in EUV spectra obtained from OSO 4, OSO 6, ATM, and full-sun measurements.
Abstract: Evidence for continuum absorption in the solar transition zone in EUV spectra obtained from OSO 4, OSO 6, ATM, and full-sun measurements is reported. This absorption shortward of 912 A is manifested everywhere on the sun's disk. It is present within network cells and boundaries of the quiet sun, in coronal holes, in active regions, above the limb, and in solar prominences. Models of the upper chromosphere and the transition zone must be modified to include an admixture of neutral hydrogen (or possibly single ionized helium) with the hotter plasma.
45 citations
TL;DR: In this article, it was shown that mass outflows in the solar transition region and corona may not start until temperatures of about 250,000 K are reached, which is the temperature at which the ionization equilibrium is no longer maintained.
Abstract: Substantial and systematic departures from ionization equilibrium can occur in the solar transition region and corona when mass outflows are present. Modeling calculations illustrate the general characteristics of the ionization balance in such regions. The presence of nonequilibrium conditions suggests a natural explanation for the extended region of EUV line emission that is observed above the solar limb. Comparison with observations of a coronal hole on the disk indicates that outflow may not start until temperatures of about 250,000 K are reached. Additional consequences include a diminution of the density discrepancy between ultraviolet and radio observations of coronal holes, and potential effects on the energy balance in solar and stellar atmospheres undergoing mass loss.
34 citations
01 Jan 1979
TL;DR: In this paper, non-Maxwellian electron velocity distribution functions, previously computed for Dupree's model of the solar transition region, were used to calculate ionization rates for ions of carbon, nitrogen, and oxygen.
Abstract: Non-Maxwellian electron velocity distribution functions, previously computed for Dupree's model of the solar transition region are used to calculate ionization rates for ions of carbon, nitrogen, and oxygen. Ionization equilibrium populations for these ions are then computed and compared with similar calculations assuming Maxwellian distribution functions for the electrons. The results show that the ion populations change (compared to the values computed with a Maxwellian) in some cases by several orders of magnitude depending on the ion and its temperature of formation.
2 citations