Showing papers on "Solar transition region published in 1985"
TL;DR: In this paper, the predicted temporal behavior of DEM for two models of energy transport in a flaring loop is compared. And the authors conclude that electron beam heating is a likely candidate for energy transport.
Abstract: Optically thin line emissiosn formed in the solar transition region provides sensitive diagnostics of the atmospheric structure at these levels. Observations of such emission lines during the impulsive phase of solar flares show that a good correlation exists between the energy input rate (as evidenced by, for example, the hard X-ray flux) and the intensity I of a given line, and thus also the differential emission measure quantity DEM = n/sup 2/dx/d ln T, where n is the density and dx/d ln T is the temperature scale length. In this paper, we calculate and contrast the predicted temporal behavior of DEM for two models of energy transport in a flaring loop. We find that a model in which the principal mechanism of energy transport is thermal conduction cannot satisfactorily reproduce the basic observational trend noted above. On the other hand, a model in which the energy is transported throughout the flaring loop principally by collisional degradation of a beam of accelerated suprathermal electrons does adequately reproduce observed behavior. We therefore conclude that electron beam heating is a likely candidate for energy transport in the impulsive phase of flares.
41 citations
TL;DR: The solar transition region in the neighborhood of prominences has been studied from observations with the Ultraviolet Spectrometer and Polarimeter of NASA's Solar Maximum Mission satellite as discussed by the authors.
Abstract: The solar transition region in the neighborhood of prominences has been studied from observations with the Ultraviolet Spectrometer and Polarimeter of NASA's Solar Maximum Mission satellite. Dopplergrams from observations of the transition-region lines C IV 1548 A and Si IV 1393 A, which are formed at about 100,000 K, give velocity amplitudes typically in the range + or - 15 km/s. Prominences are found to be located very close to dividing lines between areas of up- and down-drafts in the transition-region. The observed pattern suggests that the 100,000 K gas flows take place within arcades of magnetic loops, which most likely are part of the supporting magnetic structure for the prominence matter. An additional band of blue-ward Doppler shifts is frequently seen close to quiescent prominences. This may be the source of outward flowing matter along the helmet streamers above filament channels.
29 citations
TL;DR: In this paper, the twelve-state R-matrix calculations of electron excitation rates in Ciii by Berrington are used to derive level populations applicable to the solar transition region.
Abstract: The recent twelve-state R-matrix calculations of electron excitation rates in Ciii by Berrington are used to derive level populations applicable to the solar transition region. Line ratios R = I(2p2 3Pe - 2s2p3P°)/I(2s2p1P° - 2s2 1Se) and R2=I(2p2 1Se - 2s2p1P°)/I(2p2 3Pe - 2s2p3P°) deduced from these data in conjunction with the relevent transition probabilities are found to be in much better agreement with the observed quiet Sun values than those determined from the level population calculations of Keenan et al.
15 citations