Two-dimensional photometric analysis of emission lines in quiescent prominences

Emission lines from quiescent prominences were observed simultaneously thro ugh narrow-band interference filters, thus integrating the total line inten sities without the use of a spectrograph. Simultaneous exposures (50 ms) on three electronically connected CCD cameras at the 70 cm VTT on Tenerife as sured almost identical influence of the Earth's atmosphere and a spatial re solution of less than or equal to 1 arc sec. The resulting spatially high-r esolution two-dimensional images in H beta, H alpha, and Ca(+)8542, calibra ted in units of the disk-center intensities, allow a two-dimensional mappin g of emission ratios yielding relevant physical parameters. The emission re lation between H alpha and H beta, which depends on the total optical thick ness, confirms earlier photometric results from spectra, however, with a la rge sample of data points from six prominences. It demonstrates the saturat ion effects towards brighter prominences or prominence locations. The relat ion between Ca(+)8542 and H beta, which depends on the gas pressure, is fou nd to vary between different prominences but is nearly constant within one prominence. Its mean spatial variation of less than or equal to 30% within one prominence may be interpreted in terms of a magnetic field with variati ons of less than or equal to5%. The brightness distribution in most promine nces is not smooth but indicates preferred values, which are interpreted as superpositions of several fine structures.