Del Zanna, G;
Electron-impact excitation of Be-like Mg.
1203 - 1208.
We present an R- matrix calculation of electron- impact excitation of Be- like Mg. The calculation is similar to that one presented for Be- like Fe by Chidichimo et al. ( 2005, A& A, 430, 331), and was done with the intermediate- coupling frame transformation method and including a total of 98 fine- structure levels, up to n = 4. We find significant di. erences with the widely used n = 2 excitation rates of Keenan et al. ( 1986, Phys. Scr., 34, 216), calculated by interpolating R- matrix calculations along the Be- like sequence. We present a list of the most important transitions and a few comparisons with SOHO SUMER and CDS/ GIS spectra of the solar corona. We show that previous long- standing discrepancies between observed and predicted line intensities are now resolved. We also show how temperatures of the solar corona were significantly underestimated. For example, a coronal hole inter- plume temperature of 850 000 K found by Wilhelm et al. ( 1998, ApJ, 500, 1023) is now revised to 1 160 000 K.
|Title:||Electron-impact excitation of Be-like Mg|
|Keywords:||atomic data, techniques : spectroscopic, Sun : corona, FINE-STRUCTURE TRANSITIONS, OPTICALLY THIN PLASMAS, INCLUDING N=4 LEVELS, BERYLLIUM-LIKE IONS, ATOMIC DATA, RATE COEFFICIENTS, COLLISION STRENGTHS, EMISSION-LINES, IRON PROJECT, DATABASE|
|UCL classification:||UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Space and Climate Physics|
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