Two-dimensional photometric analysis of emission lines in quiescent prominences |
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| Authors: | Stellmacher G Wiehr E |
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| Institution: | (1) Institut d'Astrophysique CNRS, 98bis Blvd. d'Arago, 75014 Paris, France;(2) Universitäts-Sternwarte, Geismarlandstr.11, 37083 Göttingen, Germany |
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| Abstract: | Emission lines from quiescent prominences were observed simultaneously through narrow-band interference filters, thus integrating the total line intensities without the use of a spectrograph. Simultaneous exposures (50 ms) on three electronically connected CCD cameras at the 70 cm VTT on Tenerife assured almost identical influence of the Earth's atmosphere and a spatial resolution of  1 arc sec. The resulting spatially high-resolution two-dimensional images in H , H , and Ca+8542, calibrated in units of the disk-center intensities, allow a two-dimensional mapping of emission ratios yielding relevant physical parameters. The emission relation between H and H, which depends on the total optical thickness, confirms earlier photometric results from spectra, however, with a large sample of data points from six prominences. It demonstrates the saturation effects towards brighter prominences or prominence locations. The relation between Ca+8542 and H, which depends on the gas pressure, is found to vary between different prominences but is nearly constant within one prominence. Its mean spatial variation of 30% within one prominence may be interpreted in terms of a magnetic field with variations of 5%. The brightness distribution in most prominences is not smooth but indicates preferred values, which are interpreted as superpositions of several fine structures. |
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