An EUV imaging spectrograph for high-resolution observations of the solar corona

Neupert, W. M.; Epstein, Gerald L.; Thomas, R. J.; Thompson, W. T.

doi:10.1007/bf00146577

Cited by 77 publications

(23 citation statements)

References 20 publications

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“…Detailed comparisons of the more recent atomic data models of Fe xiii in the CHIANTI atomic database (Dere et al 1997) with spectra from the SERTS rocket flight experiments (Neupert et al 1992) have been performed by Young et al (1998) and Landi (2002). In particular, the latter work found that the λ196.54/λ202.04 and λ203.82/λ202.04 ratios used in the present work give density estimates in good agreement with each other and also with other ions formed at similar temperatures.…”

Section: Introductionmentioning

confidence: 99%

High-precision density measurements in the solar corona

Young

Watanabe

Hara

et al. 2008

A&A

180

189

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Aims. The EUV Imaging Spectrometer (EIS) instrument on board the Hinode satellite has access to some of the best coronal density diagnostics, and the high sensitivity of the instrument now allows electron number density, N e , measurements to an unprecedented precision of up to ±5% in active regions. This paper gives a thorough overview of data analysis issues for the best diagnostics of Fe xii and Fe xiii and assesses the accuracy of the measurements. Methods. Two density diagnostics each from Fe xii (λ186.88/λ195.12 and λ196.64/λ195.12) and Fe xiii (λ196.54/λ202.04 and λ203.82/λ202.04) are analysed in two active region datasets from 2007 May 3 and 6 that yield densities in the range 8.5 ≤ log (N e /cm −3 ) ≤ 11.0. The densities are derived using v5.2 of the CHIANTI atomic database. Blending, line fitting, and instrumental issues are discussed, and line fit parameters presented.Results. The Fe xii and Fe xiii diagnostics show broadly the same trend in density across the active region, consistent with their similar temperatures of formation. However, the high precision of the EIS measurements demonstrates significant discrepancies of up to 0.5 dex in derived log N e values, with Fe xii always giving higher densities than Fe xiii. The discrepancies may partly be due to real physical differences between the emitting regions of the two plasmas, but the dominant factor lies in the atomic models of the two ions. Two specific problems are identified for Fe xii λ196.64 and Fe xiii λ203.82: the former is found to be underestimated in strength by the CHIANTI atomic model, while the high-density limit of the λ203.82/λ202.04 ratio appears to be inaccurate in the CHIANTI atomic model. The small grating tilt of the EIS instrument is found to be very significant when deriving densities from emission lines separated by more than a few angstroms. Revised wavelengths of 196.518 ± 0.003 Å and 196.647 ± 0.003 Å are suggested for the Fe xiii λ196.54 and Fe xii λ196.64 lines, respectively.

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Section: Introductionmentioning

confidence: 99%

High-precision density measurements in the solar corona

Young

Watanabe

Hara

et al. 2008

A&A

180

189

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“…SERTS was designed to improve upon earlier solar EUV instrumentation by (1) retaining the stigmatic imaging capability of the Naval Research Laboratory spectroheliograph on Skylab (Tousey et al 1977), but with a spatial selection capability that reduced image overlap, and (2) achieving high spectral resolution. The version of SERTS flown in 1989 (SERTS-89; Neupert et al 1992) gathered EUV radiation with a grazing incidence telescope (as did subsequent SERTS flights), and carried a standard gold-coated toroidal diffraction grating. SERTS-89 observed hundreds of first-order emission lines between 235 and 450 Å, as well as dozens of second-order lines between 170 and 225 Å (Thomas & Neupert 1994;Young et al 1998).…”

Section: Introductionmentioning

confidence: 99%

UNDERFLIGHT CALIBRATION OF SOHO /CDS AND HINODE /EIS WITH EUNIS-07

Wang¹,

Thomas²,

Brosius³

et al. 2011

ApJS

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Flights of Goddard Space Flight Center's Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket in 2006 and 2007 provided updated radiometric calibrations for Solar and Heliospheric Observatory/Coronal Diagnostic Spectrometer (SOHO/CDS) and Hinode/Extreme Ultraviolet Imaging Spectrometer (Hinode/EIS). EUNIS carried two independent imaging spectrographs covering wavebands of 300-370 Å in first order and 170-205 Å in second order. After each flight, end-to-end radiometric calibrations of the rocket payload were carried out in the same facility used for pre-launch calibrations of CDS and EIS. During the 2007 flight, EUNIS, SOHO/CDS, and Hinode/EIS observed the same solar locations, allowing the EUNIS calibrations to be directly applied to both CDS and EIS. The measured CDS NIS 1 line intensities calibrated with the standard (version 4) responsivities with the standard long-term corrections are found to be too low by a factor of 1.5 due to the decrease in responsivity. The EIS calibration update is performed in two ways. One uses the direct calibration transfer of the calibrated EUNIS-07 short wavelength (SW) channel. The other uses the insensitive line pairs, in which one member was observed by the EUNIS-07 long wavelength (LW) channel and the other by EIS in either the LW or SW waveband. Measurements from both methods are in good agreement, and confirm (within the measurement uncertainties) the EIS responsivity measured directly before the instrument's launch. The measurements also suggest that the EIS responsivity decreased by a factor of about 1.2 after the first year of operation (although the size of the measurement uncertainties is comparable to this decrease). The shape of the EIS SW response curve obtained by EUNIS-07 is consistent with the one measured in laboratory prior to launch. The absolute value of the quiet-Sun He ii 304 Å intensity measured by EUNIS-07 is consistent with the radiance measured by CDS NIS in quiet regions near the disk center and the solar minimum irradiance recently obtained by CDS NIS and the Solar Dynamics Observatory/Extreme Ultraviolet Variability Experiment.

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“…The transitions corresponding to these wavelengths are listed in Table 1. the SERTS reduction and calibration procedures can be found in Neupert et al (1992) and Thomas & Neupert (1994).…”

Section: Observational Datamentioning

confidence: 99%

Extreme‐Ultraviolet Emission Lines of Sxin Solar Flare and Active Region Spectra

Keenan¹,

Katsiyannis²,

Widing³

2004

ApJ

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R-matrix calculations of electron impact excitation rates in N-like S x are used to derive theoretical emissionline intensity ratios involving 2s 2 2p 3 2s2p 4 transitions in the 189-265 Å wavelength range. A comparison of these with observational data for solar flares and active regions, obtained with the Naval Research Laboratory's S082A spectrograph on board Skylab and the Solar EUV Rocket Telescope and Spectrograph, reveals that many of the S x lines in the spectra are badly blended with emission features from other species. However, the intensity ratios Ið228:70 Å Þ=Ið264:24 Å Þ and Ið228:70 Å Þ=Ið259:49 Å Þ are found to provide useful electron density diagnostics for flares, although the latter cannot be employed for active regions, because of blending of the 259.49 Å line with an unidentified transition in these solar features.

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An EUV imaging spectrograph for high-resolution observations of the solar corona

Cited by 77 publications

References 20 publications

High-precision density measurements in the solar corona

High-precision density measurements in the solar corona

UNDERFLIGHT CALIBRATION OF SOHO /CDS AND HINODE /EIS WITH EUNIS-07

Extreme‐Ultraviolet Emission Lines of Sxin Solar Flare and Active Region Spectra

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