Extreme ultraviolet spectroscopy of the solar corona

作者: Giulio Del Zanna

DOI:

关键词: Abundance of the chemical elementsExtreme ultravioletCoronal loopAstrophysicsCoronaCoronal holeCoronal radiative lossesPhysicsSpectral lineEmission spectrum

摘要: New Extreme Ultra-Violet (EUV) observations of the solar corona, obtained by Coronal Diagnostic Spectrometer (CDS) instrument on board NASA/ESA Solar and Heliospheric Observatory (SOHO) are presented. The CDS for first time has provided opportunity observing a large number emission lines from wide range ions different elements. spectral spatial resolution allowed simultaneous application spectroscopic diagnostic techniques to determine temperature distribution, densities elemental abundances in plasma. A differential measure (DEM) technique been used infer structure element abundances. importance including DEM effects abundance analysis is demonstrated. complete in-flight cross-calibration between all detectors (NIS €115, 150-785 A), presented here time. level accuracy completeness CHIANTI atomic database, throughout this thesis, identification many hundreds observed spectra, resulting several new line identifications. An assessment €115 spectra presented, showing that, spite complexities, useful analyses. Many discrepancies (in particular with Li-like ions) theory highlighted. It shown that some these may be explained inaccurate ionization equilibrium calculations. hole densities, temperatures, DEMs, relative both off-limb (plume inter-plume regions) on-disc derived compared quiet sun values. These included (August 1996) equatorial hole, Elephant's Trunk, probably best example coronal SOHO. (N 1x10 8 cm 3 ) transition region (Ne = lxlO'° plasma were found about factor 2 lower than sun, much measures at temperatures above 106 K. Moreover, region, cell-centres holes regions show consistently higher (factor 2) those network. Relative approximately photospheric values holes, an indication variation .(neon particular) supergranular structure. On-disc EUV plumes have performed. This characterisation time, leading low-latitude plume near sun-centre. Plumes quasi-isothermal structures, T 7 - 8x10 5 Abundance analyses (using lines) reveal small FIP effect plumes, together decreased Ne/O ratio (compared photospheric).

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