6 Summary

The spatially resolved solar EUV/FUV spectra studied in this atlas, cover a wide spectral range from 670 Å to 1609 Å and provide a wealth of information on solar plasma structures from the upper chromosphere through the transition region to the corona. This information has, therefore, a tremendous diagnostic value for the emitting source. Together with the high spatial resolution of the SUMER spectrograph, compared to other solar EUV spectrometers flown during the last decades, plasma parameters of small solar features can be investigated. The atlas also provides an excellent reference for astrophysical applications. The SUMER spectrograph combines better spectral and spatial resolutions as well as coverage than any previous observations in the same wavelength range, and permits the extensive use of spectroscopic techniques in determining temperatures, pressures, densities and velocities in the upper solar atmosphere. The atlas also presents a powerful tool for the planning of future observations, i.e., to determine adequate integration times, to identify possible blends, and to select proper data extraction windows in upcoming solar studies.

Acknowledgements

We thank Tom Ayres for his help in retrieving the stellar data from the ST Science Institute archive. The SUMER project is financially supported by DLR, CNES, NASA and the ESA PRODEX Programme (Swiss contribution). SUMER is part of SOHO, the Solar and Heliospheric Observatory, of ESA and NASA. U. F. acknowledges financial support from NRL/ONR 6.1 basic research programs and NASA grants.

Figure 4: The SUMER solar-disk spectral atlas includes profiles of the average quiet Sun (black), an equatorial coronal hole (blue), and a sunspot (red). Resolved emission lines are indicated by a mark, the measured wavelength in angstrom (Å), and the identification, if available. The marks point to line lists available in the literature, where additional information about a specific line can be found. Squares ($\Box$) point to Feldman et al. (1997), circles ($\circ$) to Curdt et al. (1997), diamonds ($\Diamond$) to Kelly (1987), Cohen et al. (1978), or Sandlin et al. (1986). Triangles ($\triangle$) are new lines or identifications. Filled symbols denote lines observed in first order of diffraction, open symbols are second-order lines. Only the three least-significant digits of the wavelength values are given. If available, unidentified lines are characterized by the temperature classification of Feldman et al. (1997)(a: $T_{\rm e} <$ 3 $\times$ 105; b: $T_{\rm e} \approx$ 3 $\times$ 105; c: $T_{\rm e} \approx$ 4 $\times$ 105; d: 6 $\times$ 10 $^5 < T_{\rm e} <$ 9 $\times$ 105; e: $T_{\rm e} \approx$ 1.4 $\times$ 106; f: $T_{\rm e} \approx$ 1.8 $\times$ 106. The profiles have been radiometrically calibrated assuming first order of diffraction and the radiance axis is scaled to mW sr-1 m-2 Å-1. We have taken care of the type of photocathode (bare or KBr) when applying the radiometric calibration to different sections of the spectrum. For lines observed in second order, the right vertical axis is applicable. Note, that the sensitivity ratio between both orders, which is wavelength dependent, has been chosen for (and is only correct for) the central wavelength. Also note, that second order lines are always superimposed on a first order background. We also display in green the BN/CI ratio, which is a useful parameter for electron temperature classification. New identifications for the lines at 1286.20 and 1293.14 Å as Ca V/2 and for lines 1398.06 and 1423.86 Å as S IV have been established during the production process.

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