On-Orbit Sensitivity Evolution of the EUV Imaging Spectrometer on Hinode

Mariska, J. T.

doi:10.1007/s11207-012-0200-9

Cited by 9 publications

(23 citation statements)

References 18 publications

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“…This is assumed in the remainder of the paper. We note that this result is in stark contrast to the conclusions reached by Kamio & Mariska (2012) and Mariska (2013). We will return to this point in the conclusions.…”

Section: Sw and Lw Line Radiancescontrasting

confidence: 56%

“…We use QS observations. There are no Si vii lines in the SW channel, but Kamio & Mariska (2012) and Mariska (2013) suggested the use of the Si vii 275.3 Å vs. Fe viii 185.2 Å ratio to monitor the relative sensitivity of the LW/SW channels. We will discuss this issue below.…”

Section: Silicon and Sulfur Linesmentioning

confidence: 99%

“…This ratio was used by Kamio & Mariska (2012) and Mariska (2013) to argue that both SW and LW channels had the same decrease in sensitivity. Other ratios such as the 278.4/196 Å show similar behaviour.…”

Section: Sw/lw Ratios and Long-term Correctionmentioning

confidence: 99%

“…The radiances of the He ii 256 Å line show a clear decrease over time, and a preliminary long-term correction for all the EIS wavelengths was proposed, assuming that The He ii is severely blended, but these blends cannot explain the difference. Mariska (2013) suggested that the He ii should be discarded, and that the results of the three above-mentioned lines indicate a slow decrease of both SW and LW channels over time.…”

Section: Introductionmentioning

confidence: 99%

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A revised radiometric calibration for the Hinode/EIS instrument

Zanna¹

2013

A&A

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An assessment of the in-flight radiometric calibration of the Hinode EUV Imaging Spectrometer (EIS) is presented. This is done with the line ratio technique applied to a wide range of observations of the quiet Sun, active regions, and flares from 2006 until 2012. The best diagnostic lines and the relevant atomic data are discussed in detail. Radiances over the quiet Sun are also considered, with comparisons with previous measurements. Some departures in the shapes of the ground calibration responsivities are found at the start of the mission. These shapes do not change significantly over time, with the exception of the shorter wavelengths of the EIS short-wavelength (SW) channel, which shows some degradation. The sensitivity of the SW channel at longer wavelengths does not show significant degradation, while that of the long-wavelength (LW) channel shows a significant degradation with time. By the beginning of 2010 the responsivity of the LW channel was already lower than the values measured on the ground by a factor of two or more. A first-order correction is proposed. With this correction, the main ratios of lines in the two channels become constant to within a relative 20%, and the He ii 256 Å radiances over the quiet Sun also become constant over time. This correction removes long-standing discrepancies for a number of lines and ions, in particular those involving the strongest Fe x, Fe xiii, Fe xiv, Fe xvii, and Fe xxiv lines, where discrepancies of factors of more than two were found. These results have important implications for various EIS science analyses, in particular for measurements of temperatures, emission measures and elemental abundances.

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Section: Sw and Lw Line Radiancescontrasting

confidence: 56%

Section: Silicon and Sulfur Linesmentioning

confidence: 99%

Section: Sw/lw Ratios and Long-term Correctionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A revised radiometric calibration for the Hinode/EIS instrument

Zanna¹

2013

A&A

View full text Add to dashboard Cite

show abstract

“…The evolution of the EIS sensitivity has also been monitored through quiet-Sun observations. Mariska (2013) found that the intensities of various lines apparently decayed over time, with a time constant of about 20 years, suggesting a very stable calibration.…”

Section: Systematic Uncertaintiesmentioning

confidence: 94%

Inferring the Coronal Density Irregularity From Euv Spectra

Hahn

Savin

2016

ApJ

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Understanding the density structure of the solar corona is important for modeling both coronal heating and the solar wind. Direct measurements are difficult because of line-of-sight integration and possible unresolved structures. We present a new method for quantifying such structures using density-sensitive extreme ultraviolet line intensities to derive a density irregularity parameter, a relative measure of the amount of structure along the line of sight. We also present a simple model to relate the inferred irregularities to physical quantities, such as the filling factor and density contrast. For quiet-Sun regions and interplume regions of coronal holes, we find a density contrast of at least a factor of 3-10and corresponding filling factors of about 10%-20%. Our results are in rough agreement with other estimates of the density structures in these regions. The irregularity diagnostic provides a useful relative measure of unresolved structure in various regions of the corona.

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Are Chromospheric Nanoflares a Primary Source of Coronal Plasma?

Klimchuk

Bradshaw

2014

ApJ

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It has been suggested that the hot plasma of the solar corona comes primarily from impulsive heating events, or nanoflares, that occur in the lower atmosphere, either in the upper part of the ordinary chromosphere or at the tips of type II spicules. We test this idea with a series of hydrodynamic simulations. We find that synthetic Fe XII (195) and Fe XIV (274) line profiles generated from the simulations disagree dramatically with actual observations. The integrated line intensities are much too faint; the blue shifts are much too fast; the blue-red asymmetries are much too large; and the emission is confined to low altitudes. We conclude that chromospheric nanoflares are not a primary source of hot coronal plasma. Such events may play an important role in producing the chromosphere and powering its intense radiation, but they do not, in general, raise the temperature of the plasma to coronal values. Those cases where coronal temperatures are reached must be relatively uncommon. The observed profiles of Fe XII and Fe XIV come primarily from plasma that is heated in the corona itself, either by coronal nanoflares or a quasi-steady coronal heating process. Chromospheric nanoflares might play a role in generating waves that provide this coronal heating.

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On-Orbit Sensitivity Evolution of the EUV Imaging Spectrometer on Hinode

Abstract: K in the quiet-Sun data exhibit solar-cycle effects.

Cited by 9 publications

References 18 publications

A revised radiometric calibration for the Hinode/EIS instrument

A revised radiometric calibration for the Hinode/EIS instrument

Inferring the Coronal Density Irregularity From Euv Spectra

Are Chromospheric Nanoflares a Primary Source of Coronal Plasma?

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