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Astron. Astrophys. 332, 325-338 (1998)


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A statistical approach to the investigation of fine structure of solar prominences

S. Pojoga 1, 3, A.G. Nikoghossian 2, 3 and Z. Mouradian 3

1 Astronomical Institute of Romanian Academy, RO-75212 Bucharest, Romania
2 Byurakan Astrophysical Observatory, 378433 Byurakan, Armenia
3 Observatoire de Paris-Meudon, DASOP, F-92195 Meudon Cedex, France

Received 21 October 1997 / Accepted 11 December 1997

Abstract

A statistical approach is proposed for the study of the prominence fine structure in EUV lines ([FORMULA] to [FORMULA] K). For different regions of several solar prominences, the distributions of the observed intensities, and their averaged characteristics (mean intensity and relative variance) are determined. We develop a statistical model, assuming that the observed intensities and their fluctuations are generated by a random number of fine-structure elements along the line-of-sight. Different models are considered, for the lines formed in the cool plasma and in the hot transition zone. For the structural components, two geometries - slabs and threads - are assumed. We compare the statistical characteristics of the intensity, inferred from theoretical models, with those obtained from observations. The influence of the geometrical model on the degree of the brightness variations is analysed. The expected number of fine-structure components along the line-of-sight is also derived. We show that, generally, the geometry is not of major importance for the study of the spatial brightness fluctuations. A relative small mean number of fine-structure elements along the line-of-sight is determined.

Key words: Sun: prominences – Sun: transition region – radiative transfer

Send offprint requests to: S. Pojoga

© European Southern Observatory (ESO) 1998

Online publication: March 10, 1998
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