Chromospheric polarimetry through multiline observations of the 850-nm spectral region – II. A magnetic flux tube scenario

Noda, C. Quintero; Kato, Yoshiaki; Katsukawa, Y.; Oba, Takayoshi; Rodríguez, J. de la Cruz; Carlsson, Mats; Shimizu, Toshifumi; Suárez, D. Orozco; Cobo, B. Ruiz; Kubo, Masahito; Anan, Tetsu; Ichimoto, Kiyoshi; Suematsu, Y.

doi:10.1093/mnras/stx2022

Cited by 14 publications

(12 citation statements)

References 24 publications

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“…It shows that the average LOS magnetic field obtained with the WFA is around 250 ± 50 G until ∼10:47 UT, decreasing later down to 180 ± 30 G. Increased gradients in Stokes I, as those observed in the flare, lead to increased polarization signals and this is described in the WFA (Equations 1 & 2). Gradients of Stokes I with respect to wavelength then certainly contribute to the observed enhanced amplitude of polarization signals (as in de la Cruz Rodríguez et al 2012, Quintero Noda et al 2017. However, such increases did not lead to WFA reproducing the flaring profiles without an increase in magnetic field.…”

Section: Analysis and Resultsmentioning

confidence: 89%

“…In this regime, the Stokes profiles can be expressed as (Landi (1) and (2)). Gradients of Stokes I with respect to wavelength then certainly contribute to the observed enhanced amplitude of polarization signals (as in de la Cruz Rodríguez et al 2012;Quintero Noda et al 2017). However, such increases did not lead to WFA reproducing the flaring profiles without an increase in magnetic field.…”

Section: Analysis and Resultsmentioning

confidence: 97%

“…Furthermore, the NLTE radiative transfer code NICOLE (Socas-Navarro et al 2015) allows us to perform the inversion of observed Ca II 8542 Å (hereafter Ca 8542) Stokes profiles and the construction of semiempirical model atmospheres. Such inversions have been successfully performed for spectropolarimetric Ca 8542 observations and 3D magnetohydrodynamical simulations of solar features in the umbra and penumbra of sunspots (de la Cruz Rodríguez et al 2013;Henriques et al 2017), granular-size magnetic elements (magnetic bubbles) in an active region, and magnetic flux tubes (de la Cruz Rodríguez et al 2015a;Quintero Noda et al 2017). Recently, Kuridze et al (2017) performed NICOLE inversions of high-resolution spectroscopic data in the Ca 8542 line and found that the temperature in the middle and upper chromosphere close to the flare peak is enhanced up to ∼6.5-20 kK between logτ∼−3.5 and−5.5, decreasing gradually to pre-flare temperatures of ∼5-10 kK approximately 15 minutes after the peak.…”

Section: Introductionmentioning

confidence: 99%

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Spectropolarimetric Inversions of the Ca ii 8542 Å Line in an M-class Solar Flare

Kuridze

Henriques

Mathioudakis

et al. 2018

ApJ

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We study the M1.9 class solar flare SOL2015-09-27T10:40 UT using high-resolution full-Stokes imaging spectropolarimetry of the Ca ii 8542 Å line obtained with the CRISP imaging spectropolarimeter at the Swedish 1-m Solar Telescope. Spectropolarimetric inversions using the non-LTE code NICOLE are used to construct semi-empirical models of the flaring atmosphere to investigate the structure and evolution of the flare temperature and magnetic field. A comparison of the temperature stratification in flaring and non-flaring areas reveals strong heating of the flare ribbon during the flare peak. The polarization signals of the ribbon in the chromosphere during the flare maximum become stronger when compared to its surroundings and to pre-and post-flare profiles. Furthermore, a comparison of the response functions to perturbations in the line-of-sight magnetic field and temperature in flaring and non-flaring atmospheres shows that during the flare the Ca ii 8542 Å line is more sensitive to the lower atmosphere where the magnetic field is expected to be stronger. The chromospheric magnetic field was also determined with the weak-field approximation which led to results similar to those obtained with the NICOLE inversions.

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Section: Analysis and Resultsmentioning

confidence: 89%

Section: Analysis and Resultsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Spectropolarimetric Inversions of the Ca ii 8542 Å Line in an M-class Solar Flare

Kuridze

Henriques

Mathioudakis

et al. 2018

ApJ

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“…We have taken one snapshot from a publicly available enhanced network simulation (Carlsson et al 2016) performed with the Bifrost code (Gudiksen et al 2011). Snapshots from this simulation have been extensively used in previous studies and have been the workhorse of polarized line formation studies in recent years using the same spectral line (e.g., Štěpán & Trujillo Bueno 2016;Quintero Noda et al 2017;Jurčák et al 2018;.…”

Section: Tests With An 3d Rmhd Simulationmentioning

confidence: 99%

Stratification of canopy magnetic fields in a plage region

Morosin

Rodríguez

Vissers

et al. 2020

A&A

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Context. The role of magnetic fields in the chromospheric heating problem remains greatly unconstrained. Most theoretical predictions from numerical models rely on a magnetic configuration, field strength, and connectivity; the details of which have not been well established with observational studies for many chromospheric scenarios. High-resolution studies of chromospheric magnetic fields in plage are very scarce or non existent in general. Aims. Our aim is to study the stratification of the magnetic field vector in plage regions. Previous studies predict the presence of a magnetic canopy in the chromosphere that has not yet been studied with full-Stokes observations. We use high-spatial resolution full-Stokes observations acquired with the CRisp Imaging Spectro-Polarimeter (CRISP) at the Swedish 1-m Solar Telescope in the Mg I 5173 Å, Na I 5896 Å and Ca II 8542 Å lines. Methods. We have developed a spatially-regularized weak-field approximation (WFA) method, based on the idea of spatial regularization. This method allows for a fast computation of magnetic field maps for an extended field of view. The fidelity of this new technique has been assessed using a snapshot from a realistic 3D magnetohydrodynamics simulation. Results. We have derived the depth-stratification of the line-of-sight component of the magnetic field from the photosphere to the chromosphere in a plage region. The magnetic fields are concentrated in the intergranular lanes in the photosphere and expand horizontally toward the chromosphere, filling all the space and forming a canopy. Our results suggest that the lower boundary of this canopy must be located around 400 − 600 km from the photosphere. The mean canopy total magnetic field strength in the lower chromosphere (z ≈ 760 km) is 658 G. At z = 1160 km, we estimate ⟨B∥⟩ ≈ 417 G. Conclusions. In this study we propose a modification to the WFA that improves its applicability to data with a worse signal-to-noise ratio. We have used this technique to study the magnetic properties of the hot chromospheric canopy that is observed in plage regions. The methods described in this paper provide a quick and reliable way of studying multi layer magnetic field observations without the many difficulties inherent to other inversion methods.

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“…The Ca ii 8542 Å line has become one of the foremost chromospheric diagnostics for temperatures, line-of-sight velocities, and the magnetic field vector (see, e.g., Socas-Navarro et al 2000b;López Ariste et al 2001;Pietarila et al 2007;de la Cruz Rodríguez et al 2012, 2015aQuintero Noda et al 2017;Henriques et al 2017;Centeno 2018;Díaz Baso et al 2019a).…”

Section: The Ca II 8542 å Line In Plage Regionsmentioning

confidence: 99%

Inference of the chromospheric magnetic field configuration of solar plage using the Ca II 8542 Å line

Pietrow

Kiselman

Rodríguez

et al. 2020

A&A

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Context. It has so far proven impossible to reproduce all aspects of the solar plage chromosphere in quasi-realistic numerical models. The magnetic field configuration in the lower atmosphere is one of the few free parameters in such simulations. The literature only offers proxy-based estimates of the field strength, as it is difficult to obtain observational constraints in this region. Sufficiently sensitive spectro-polarimetric measurements require a high signal-to-noise ratio, spectral resolution, and cadence, which are at the limit of current capabilities. Aims. We use critically sampled spectro-polarimetric observations of the Ca II 8542 Å line obtained with the CRISP instrument of the Swedish 1-m Solar Telescope to study the strength and inclination of the chromospheric magnetic field of a plage region. This will provide direct physics-based estimates of these values, which could aid modelers to put constraints on plage models. Methods. We increased the signal-to-noise ratio of the data by applying several methods including deep learning and PCA. We estimated the noise level to be 1 × 10−3 Ic. We then used STiC, a non-local thermodynamic equilibrium inversion code to infer the atmospheric structure and magnetic field pixel by pixel. Results. We are able to infer the magnetic field strength and inclination for a plage region and for fibrils in the surrounding canopy. In the plage we report an absolute field strength of |B| = 440 ± 90 G, with an inclination of 10° ±16° with respect to the local vertical. This value for |B| is roughly double of what was reported previously, while the inclination matches previous studies done in the photosphere. In the fibrillar region we found |B| = 300 ± 50 G, with an inclination of 50° ±13°.

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Chromospheric polarimetry through multiline observations of the 850-nm spectral region – II. A magnetic flux tube scenario

Cited by 14 publications

References 24 publications

Spectropolarimetric Inversions of the Ca ii 8542 Å Line in an M-class Solar Flare

Spectropolarimetric Inversions of the Ca ii 8542 Å Line in an M-class Solar Flare

Stratification of canopy magnetic fields in a plage region

Inference of the chromospheric magnetic field configuration of solar plage using the Ca II 8542 Å line

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Chromospheric polarimetry through multiline observations of the 850-nm spectral region – II. A magnetic flux tube scenario

Cited by 14 publications

References 24 publications

Spectropolarimetric Inversions of the Ca ii 8542 Å Line in an M-class Solar Flare

Spectropolarimetric Inversions of the Ca ii 8542 Å Line in an M-class Solar Flare

Stratification of canopy magnetic fields in a plage region

Inference of the chromospheric magnetic field configuration of solar plage using the Ca II 8542 Å line

Contact Info

Product

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Inference of the chromospheric magnetic field configuration of solar plage using the Ca II 8542 Å line