AAS 204th Meeting, June 2004
Session 51 Improving Our Understanding of Solar and Stellar Coronae
SPD Topical Session, Wednesday, June 2, 2004, 8:30-10:00am, 704/706

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[51.05] Laboratory Measurements for Developing Reliable Diagnostics of Stellar Coronae in the Extreme Ultraviolet and Soft X-ray Spectral Regions

J. K. Lepson (Space Sciences Laboratory, UC Berkeley)

{\em Chandra\/} and {\em XMM-Newton\/} observations have greatly expanded our knowledge of the spectral emission of stellar coronae, revealing a complexity in the extreme ultraviolet and soft x-ray bands that complements past solar observations. The new observations have highlighted various shortcomings in our understanding of the spectral emission. For example, spectra in this region have many unidentified or possibly misidentified lines. Therefore, established spectral diagnostics can be impaired by previously unrecognized line blends.

We are using the Livermore electron beam ion traps to simulate this emission in the laboratory. We are producing a complete catalogue of astrophysically relevant emission lines in the extreme ultraviolet and soft x-ray regions. From this catalogue we identify lines, reassess spectral diagnostics, and develop new diagnostics. Our measurements, for example, have increased the number of lines for \ion{S}{8}--\ion{S}{13} from 29 to 109. Measurements of iron, argon, sulfur, silicon, and magnesium are allowing us to identify previously unassigned lines in solar and stellar spectra. Moreover, we have identified a novel magnetic field diagnostic in neon-like ions. We have also reevaluated the diagnostic utility of the \ion{Fe}{17} 3C and 3D lines, previously considered to be a prime diagnostic of opacity, instead showing them to be of use as a diagnostic of electron temperature.

Research at the University of California Lawrence Livermore National Laboratory conducted under the auspices of the Department of Energy and supported by a NASA SARA grant.

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