A Comparison of Theoretical mgvi Emission Line Strengths with Active-Region Observations From Serts

Abstract

R-matrix calculations of electron impact excitation rates in N-like Mg vi are used to derive theoretical electron-density-sensitive emission line ratios involving 2s ²2p ³−2s2p ⁴transitions in the 269–403 Å wavelength range. A comparison of these with observations of a solar active region, obtained during the 1989 flight of the Solar EUV Rocket Telescope and Spectrograph (SERTS), reveals good agreement between theory and observation for the 2s ²2p ^{3 4} S−2s2p ^{4 4} Ptransitions at 399.28, 400.67, and 403.30 Å, and the 2s ²2p ^{3 2} P−2s2p ^{4 2} Dlines at 387.77 and 387.97 Å. However, intensities for the other lines attributed to Mg vi in this spectrum by various authors do not match the present theoretical predictions. We argue that these discrepancies are not due to errors in the adopted atomic data, as previously suggested, but rather to observational uncertainties or mis-identifications. Some of the features previously identified as Mg vi lines in the SERTS spectrum, such as 291.36 and 293.15 Å, are judged to be noise, while others (including 349.16 Å) appear to be blended.