The In-Flight Performance of the SOHO/CDS Grazing Incidence Spectrometer

Kuin, N. P. M.; Zanna, G. Del

doi:10.1007/s11207-007-0306-7

Cited by 7 publications

(7 citation statements)

References 8 publications

(11 reference statements)

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“…The in-flight radiometric calibration of the GIS channels (only the pinhole and slits) is described in Del Zanna et al. (2001a) and Kuin and Del Zanna (2007). No significant degradation of the GIS sensitivity was found.…”

Section: The Solar Xuv Spectrummentioning

confidence: 99%

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Solar UV and X-ray spectral diagnostics

Zanna

Mason

2018

Living Rev Sol Phys

222

139

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X-ray and ultraviolet (UV) observations of the outer solar atmosphere have been used for many decades to measure the fundamental parameters of the solar plasma. This review focuses on the optically thin emission from the solar atmosphere, mostly found at UV and X-ray (XUV) wavelengths, and discusses some of the diagnostic methods that have been used to measure electron densities, electron temperatures, differential emission measure (DEM), and relative chemical abundances. We mainly focus on methods and results obtained from high-resolution spectroscopy, rather than broad-band imaging. However, we note that the best results are often obtained by combining imaging and spectroscopic observations. We also mainly focus the review on measurements of electron densities and temperatures obtained from single ion diagnostics, to avoid issues related to the ionisation state of the plasma. We start the review with a short historical introduction on the main XUV high-resolution spectrometers, then review the basics of optically thin emission and the main processes that affect the formation of a spectral line. We mainly discuss plasma in equilibrium, but briefly mention non-equilibrium ionisation and non-thermal electron distributions. We also summarise the status of atomic data, which are an essential part of the diagnostic process. We then review the methods used to measure electron densities, electron temperatures, the DEM, and relative chemical abundances, and the results obtained for the lower solar atmosphere (within a fraction of the solar radii), for coronal holes, the quiet Sun, active regions and flares.

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Section: The Solar Xuv Spectrummentioning

confidence: 99%

“…The spectra obtained with the pinhole slit have been calibrated in-flight (Del Zanna et al. 2001a; Kuin and Del Zanna 2007), but the long slit observations are impossible to calibrate, since the detectors were not fully illuminated in this case.…”

Section: Measurements Of Electron Temperaturesmentioning

confidence: 99%

Solar UV and X-ray spectral diagnostics

Zanna

Mason

2018

Living Rev Sol Phys

222

139

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“…The results of the calibration work concerning the SOHO CDS Grazing Incidence Spectrograph (GIS) were published in Kuin & Del Zanna (2007), while those for the Normal Incidence Spectrograph (NIS) are summarised in Del hereafter Paper I).…”

Section: Introductionmentioning

confidence: 99%

The EUV spectrum of the Sun: SOHO CDS NIS irradiances from 1998 until 2010

Zanna

Andretta

2011

A&A

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We present extreme-ultraviolet (EUV) irradiances of the Sun taken during the 1998-2010 period from the Solar and Heliospheric Observatory (SoHO) Coronal Diagnostic Spectrometer (CDS) Normal Incidence Spectrograph (NIS). They were obtained from NIS full-Sun radiance observations, and represent the first set of EUV spectral observations spanning a solar cycle. We compare the CDS line irradiances with those obtained from rocket measurements, one that flew in May 1997 and one in April 2008, together with the Thermosphere Ionosphere Mesosphere Energetics Dynamics (TIMED) Solar EUV Experiment (SEE) EUV Grating Spectrograph (EGS) and various historical records. Excellent agreement (to within a relative 20%) is found in most cases, with a few notable exceptions. Lines formed in the transition region show very small changes with the solar cycle, with the exception of the helium lines. The irradiances of lines formed around 1 MK already change during the cycle by a factor ∼5; for hotter lines (2.5 MK) the variability reaches factors of the order of 40. For lines formed around 1-3 MK, and to a less extent, the helium lines, we find a good linear correlation between CDS irradiances and the 10.7 cm radio flux, although each line has a different coefficient. No correlation is found for the transition-region lines. Significant discrepancies between the observed irradiances and those modelled is found. This confirms the importance in obtaining EUV spectral measurements of the solar irradiance.

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“…Because the Zr filter has no absorption edge near 171Å (see Figure 12, inset), we believe the ratio of near-unity is quite robust. A quiet-Sun spectrum obtained in early 1997 from SOHO/GIS shows a 171/174Å line ratio of 1.3 (see Figure 2 of Kuin and Del Zanna, 2007), and the full-disk rocket spectrum of 04 April 1969 (obtained during a period of some solar activity) shows a ratio 1.0 (Malinovsky and Heroux, 1973).…”

Section: Discussionmentioning

confidence: 99%

“…SOHO/CDS/GIS has one channel (150 to 220 Å) that overlaps CHIPS, but shows spectral "ghosts" and temporal variations in throughput that require careful calibration (Kuin and Del Zanna, 2007) to provide acurate line intensities and ratios.…”

Section: Introductionmentioning

confidence: 99%

EUV Spectra of the Full Solar Disk: Analysis and Results of the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS)

2010

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We analyze EUV spectra of the full solar disk from the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) spanning a period of two years. The observations were obtained via a fortuitous off-axis light path in the 140 -275 Å passband. The general appearance of the spectra remained relatively stable over the two-year time period, but did show significant variations of up to 25% between two sets of Fe lines that show peak emission at 1 MK and 2 MK. The variations occur at a measured period of 27.2 days and are caused by regions of hotter and cooler plasma rotating into, and out of, the field of view. The CHI-ANTI spectral code is employed to determine plasma temperatures, densities, and emission measures. A set of five isothermal plasmas fit the full-disk spectra well. A 1 -2 MK plasma of Fe contributes 85% of the total emission in the CHIPS passband. The standard Differential Emission Measures (DEMs) supplied with the CHIANTI package do not fit the CHIPS spectra well as they over-predict emission at temperatures below log 10 T = 6.0 and above log 10 T = 6.3. The results are important for cross-calibrating TIMED, SORCE, SOHO/EIT, and CDS/GIS, as well as the recently launched Solar Dynamics Observatory.

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The In-Flight Performance of the SOHO/CDS Grazing Incidence Spectrometer

Cited by 7 publications

References 8 publications

Solar UV and X-ray spectral diagnostics

Solar UV and X-ray spectral diagnostics

The EUV spectrum of the Sun: SOHO CDS NIS irradiances from 1998 until 2010

EUV Spectra of the Full Solar Disk: Analysis and Results of the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS)

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