Electron density-dependent intensity ratios of highly ionized iron lines - A comparison of theory and experiment

Stratton, B. C.; Moos, H. W.; Finkenthal, M.

doi:10.1086/184249

Cited by 25 publications

(21 citation statements)

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“…The spectrum shows a multitude of iron lines near 100 Å, which are of interest to astrophysics and as tokamak diagnostics. [6][7][8] Spectral resolution of 0.10 Å was achieved, which is similar to that achieved at the short wavelengths.…”

Section: B Extended Wavelength Coveragesupporting

confidence: 72%

Time-resolved x-ray and extreme ultraviolate spectrometer for use on the National Spherical Torus Experiment

Beiersdörfer

Lepson

Bitter

et al. 2008

Review of Scientific Instruments

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We describe upgrades to a compact grazing-incidence spectrometer utilized on the National Spherical Torus Experiment for monitoring light and heavy impurities. A fast-readout charge couple device camera has been implemented that allows the recording of spectra with up to 25 ms time integration. This capability is used to study the time evolution of the K-shell emission of hydrogenlike and heliumlike boron, carbon, nitrogen, and oxygen between 10 and 65 A. Different camera positioning pieces have been employed to extend the possible spectral range to as high as 140. Several lines that cannot be ascribed to the usual elements found in the plasma have been observed in this spectral range, although often only in a few isolated discharges.

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Section: B Extended Wavelength Coveragesupporting

confidence: 72%

Time-resolved x-ray and extreme ultraviolate spectrometer for use on the National Spherical Torus Experiment

Beiersdörfer

Lepson

Bitter

et al. 2008

Review of Scientific Instruments

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“…The uncertainties for the Linsky et al and Mathioudakis (1999) observations are those quoted by these authors, and the Dupree et al (1993) uncertainty set equal to the average of the Linsky et al uncertainties. We also include a solar‐flare value from the OSO‐5 spacecraft (Kastner, Neupert & Swartz 1974; Mason et al 1984: uncertainty estimated from the calibration necessary in this measurement) and values from the Princeton Large Torus (PLT) tokamak with electron densities measured by a microwave interferometer (Stratton, Moos & Finkenthal 1984; Stratton et al 1985). With the uncertainties on the Capella and solar points, it would seem that none of the points are much above the low‐density limit, i.e.…”

Section: Discussionmentioning

confidence: 99%

“…The Capella points are labelled TP (this paper), L (Linsky et al 1998); M (Mathioudakis 1999); D (Dupree et al 1993), and the solar point S (Mason et al 1984) – the densities at which these points are plotted do not have significance. The PLT points are labelled T1 (Stratton et al 1985) and T2 (Stratton et al 1984).…”

Section: Discussionmentioning

confidence: 99%

X-ray and extreme-ultraviolet emission from the coronae of Capella

Phillips

Mathioudakis

Huenemoerder

et al. 2001

Monthly Notices of the Royal Astronomical Society

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The primary objective of this work is the analysis and interpretation of coronal observations of Capella obtained in 1999 September with the High Energy Transmission Grating Spectrometer on the Chandra X‐ray Observatory and the Extreme Ultraviolet Explorer (EUVE). He‐like lines of O (O vii) are used to derive a density of 1.7×1010 cm−3 for the coronae of the binary, consistent with the upper limits derived from Fe xxi, Ne ix and Mg xi line ratios. Previous estimates of the electron density based on Fe xxi should be considered as upper limits. We construct emission measure distributions and compare the theoretical and observed spectra to conclude that the coronal material has a temperature distribution that peaks around 4–6 MK, implying that the coronae of Capella were significantly cooler than in the previous years. In addition, we present an extended line list with over 100 features in the 5–24 Å wavelength range, and find that the X‐ray spectrum is very similar to that of a solar flare observed with SMM. The observed to theoretical Fe xvii 15.012‐Å line intensity reveals that opacity has no significant effect on the line flux. We derive an upper limit to the optical depth, which we combine with the electron density to derive an upper limit of 3000 km for the size of the Fe xvii emitting region. In the same context, we use the Si iv transition region lines of Capella from HST/Goddard High‐Resolution Spectrometer observations to show that opacity can be significant at T=105 K, and derive a path‐length of ≈75 km for the transition region. Both the coronal and transition region observations are consistent with very small emitting regions, which could be explained by small loops over the stellar surfaces.

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“…These transitions have been studied extensively in the laboratory (see, e.g. Kononov et al 1976;Stratton et al 1984), partly because they offer many line ratios that can be used to measure electron densities. Accurate wavelength measurements are also from laboratory spectra, for example from Sugar & Rowan (1995) for lines from the Fe xx-Fe xxiii ions.…”

Section: Introductionmentioning

confidence: 99%

Spectral diagnostics with the SDO EVE flare lines

Zanna¹,

Woods

2013

A&A

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The diagnostic use of the soft X-ray and EUV lines observed with the Solar Dynamics Observatory (SDO) Extreme ultraviolet Variability Experiment (EVE) is discussed. We focus on all the flare lines observed in the 80-640 Å range (mainly due to Fe xviii−Fe xxiv), showing their use to measure temperatures, emission measures, densities, and chemical abundances. We discuss their identification at the EVE resolution, by using the latest atomic data, and by assessing possible sources of blending, taking into account higher-resolution solar spectra. We present observations of four flares, and study in more detail the gradual phase peak of the 7 March 2012 X5.6 flare. Good agreement between observations and theory is found in most cases, and the best lines for diagnostics are recommended. We found reasonable densities (10 11.2 cm −3 from Fe xxi lines), but isothermal temperatures (12 MK) lower than those estimated with GOES. We show that EVE can be used to measure relative elemental abundance, and find photospheric argon/iron and calcium/iron abundances. We also show that lines normally formed in the quiet Sun in the low transition region such as O III are the best to study the impulsive phase.

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Electron density-dependent intensity ratios of highly ionized iron lines - A comparison of theory and experiment

Cited by 25 publications

References 0 publications

Time-resolved x-ray and extreme ultraviolate spectrometer for use on the National Spherical Torus Experiment

Time-resolved x-ray and extreme ultraviolate spectrometer for use on the National Spherical Torus Experiment

X-ray and extreme-ultraviolet emission from the coronae of Capella

Spectral diagnostics with the SDO EVE flare lines

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