EUV Emission Lines and Diagnostics Observed with Hinode/EIS

Young, Peter R.; Zanna, Del Giulio; Mason, H. E.; Dere, K. P.; Landi, E.; Landini, M.; Doschek, G. A.; Brown, C. M.; Culhane, Len; Harra, L. K.; Watanabe, Tetsuya; Hara, Hirohisa

doi:10.1093/pasj/59.sp3.s857

Cited by 193 publications

(133 citation statements)

References 10 publications

(8 reference statements)

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“…Instrumental effects of slit tilt and orbital variation in the line centroid position due to thermal drift were removed. In the cases of Si vii 275.35Å and Fe xv 284.16Å data (T≈ 0.6 and 2 MK, respectively; Young et al, 2007), calibrated spectra were fitted with a single gaussian function in order to Name Content i compare* intensity comparison of the three spectral lines i evolution* intensity evolution for each spectral line iv 4panels* Top panels: intensity and velocity of the Fe xii line Bottom panels: velocities of the Si vii and Fe xv lines iv compare* comparison of intensity to velocity for each spectral line v compare* velocity comparison of the three spectral lines v evolution* velocity evolution for each spectral line obtain the line centre for each spectral profile. Reference wavelengths were taken from an average value obtained in a relatively quiescent Sun patch of each raster.…”

Section: Observations and Data Reductionmentioning

confidence: 97%

“…For the core EIS Fe xii emission line at 195.12Å(T ≈ 1.4 MK; Young et al, 2007;Del Zanna, 2008), calibrated spectra were fitted using both single and double gaussian functions. The latter analysis, with more free parameters in the fitting function, is only performed with Fe xii emission line because of its stronger signal over noise ratio.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

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The 3D Geometry of Active Region Upflows Deduced from Their Limb-to-Limb Evolution

Démoulin

Baker²,

Mandrini

et al. 2013

Sol Phys

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We analyse the evolution of coronal plasma upflows from the edges of AR 10978, which has the best limb-to-limb data coverage with Hinode's EUV Imaging Spectrometer (EIS). We find that the observed evolution is largely due to the solar rotation progressively changing the viewpoint of nearly stationary flows. From the systematic changes in the upflow regions as a function of distance from disc centre, we deduce their 3D geometrical properties as inclination and angular spread in three coronal lines (Si vii, Fe xii, Fe xv). In agreement with magnetic extrapolations, we find that the flows are thin, fan-like structures rooted in quasi separatrix layers (QSLs). The fans are tilted away from the AR centre. The highest plasma velocities in these three spectral lines have similar magnitudes and their heights increase with temperature. The spatial location and extent of the upflow regions in the Si vii, Fe xii and Fe xv lines are different owing to (i) temperature stratification and (ii) line of sight integration of the spectral profiles with significantly different backgrounds. We conclude that we sample the same flows at different temperatures. Further, we find that the evolution of line widths during the disc passage is compatible with a broad range of velocities in the flows. Everything considered, our results are compatible with the AR upflows originating from reconnections along QSLs between over-pressure AR loops and neighboring under-pressure loops. The flows are driven along magnetic field lines by a pressure gradient in a stratified atmosphere. We propose that, at any given time, we observe the superposition of flows created by successive reconnections, leading to a broad velocity distribution.

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Section: Observations and Data Reductionmentioning

confidence: 97%

Section: Observations and Data Reductionmentioning

confidence: 99%

The 3D Geometry of Active Region Upflows Deduced from Their Limb-to-Limb Evolution

Démoulin

Baker²,

Mandrini

et al. 2013

Sol Phys

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“…Observations of the "moss" at the ends of hot loops provide constraints on the energy losses by downward conduction (Fletcher & de Pontieu 1999;Martens et al 2000;Warren et al 2008;Winebarger et al 2011), and measurements of plasma density can provide constraints on the spatial distribution of the heating (Fludra et al 2017). Second, the model should reproduce the observed spectral line widths, which are broadened in excess of their thermal widths (e.g., Doschek et al 2007;Young et al 2007;Tripathi et al 2009;Warren et al 2011;Tripathi et al 2011;Tian et al 2011Tian et al , 2012aDoschek 2012;Brooks & Warren 2016;Testa et al 2016). The observed non-thermal broadening provides constraints on unresolved reconnection outflows in the corona, and on the velocity amplitudes of MHD waves.…”

Section: Introductionmentioning

confidence: 99%

The Heating of Solar Coronal Loops by Alfvén Wave Turbulence

Ballegooijen¹,

Asgari-Targhi

Voß

2017

ApJ

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In this paper we further develop a model for the heating of coronal loops by Alfvén wave turbulence (AWT). The Alfvén waves are assumed to be launched from a collection of kilogauss flux tubes in the photosphere at the two ends of the loop. Using a three-dimensional magneto-hydrodynamic (MHD) model for an active-region loop, we investigate how the waves from neighboring flux tubes interact in the chromosphere and corona. For a particular combination of model parameters we find that AWT can produce enough heat to maintain a peak temperature of about 2.5 MK, somewhat lower than the temperatures of 3 -4 MK observed in the cores of active regions. The heating rates vary strongly in space and time, but the simulated heating events have durations less than 1 minute and are unlikely to reproduce the observed broad Differential Emission Measure distributions of active regions. The simulated spectral line non-thermal widths are predicted to be about 27 km s −1 , which is high compared to the observed values. Therefore, the present AWT model does not satisfy the observational constraints. An alternative "magnetic braiding" model is considered in which the coronal field lines are subject to slow random footpoint motions, but we find that such long period motions produce much less heating than the shorter period waves launched within the flux tubes. We discuss several possibilities for resolving the problem of producing sufficiently hot loops in active regions.

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“…Recently, Young et al (2007) have published a quiet-Sun extreme ultraviolet (EUV) spectrum in the ranges 170−211 Å and 246−292 Å, as observed on 2006 December 23 by the Hinode EUV Imaging Spectrometer (EIS).…”

Section: Introductionmentioning

confidence: 99%

Soft X-ray coronal spectra at low activity levels observed by RESIK

Sylwester

Phillips³

2010

A&A

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Context. The quiet-Sun X-ray emission is important for deducing coronal heating mechanisms, but it has not been studied in detail since the Orbiting Solar Observatory (OSO) spacecraft era. Bragg crystal spectrometer X-ray observations have generally concentrated on flares and active regions. The high sensitivity of the RESIK (REntgenovsky Spectrometer s Izognutymi Kristalami) instrument on the CORONAS-F solar mission has enabled the X-ray emission from the quiet corona to be studied in a systematic way for the first time. Aims. Our aim is to deduce the physical conditions of the non-flaring corona from RESIK line intensities in several spectral ranges using both isothermal and multithermal assumptions. Methods. We selected and analyzed spectra in 312 quiet-Sun intervals in January and February 2003, sorting them into 5 groups according to activity level. For each group, the fluxes in selected spectral bands have been used to calculate values of parameters for the best-fit that leads to intensities characteristic of each group. We used both isothermal and multitemperature assumptions, the latter described by differential emission measure (DEM) distributions. RESIK spectra cover the wavelength range (3.3−6.1 Å). This includes emission lines of highly ionized Si, S, Cl, Ar, and K, which are suitable for evaluating temperature and emission measure, were used. Results. The RESIK spectra during these intervals of very low solar activity for the first time provide information on the temperature structure of the quiet corona. Although most of the emission seems to arise from plasma with a temperature between 2 MK and 3 MK, there is also evidence of a hotter plasma (T ∼ 10 MK) with an emission measure 3 orders smaller than the cooler component. Neither coronal nor photospheric element abundances appear to describe the observed spectra satisfactorily.

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EUV Emission Lines and Diagnostics Observed with Hinode/EIS

Cited by 193 publications

References 10 publications

The 3D Geometry of Active Region Upflows Deduced from Their Limb-to-Limb Evolution

The 3D Geometry of Active Region Upflows Deduced from Their Limb-to-Limb Evolution

The Heating of Solar Coronal Loops by Alfvén Wave Turbulence

Soft X-ray coronal spectra at low activity levels observed by RESIK

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