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

Pietrow, A. G. M.; Kiselman, Dan; Rodríguez, J. de la Cruz; Baso, C. J. Díaz; Yabar, A. Pastor; Yadav, Rahul

doi:10.1051/0004-6361/202038750

Cited by 28 publications

(23 citation statements)

References 69 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Remaining smallscale seeing-induced deformations were removed according to the recipe by Henriques (2012), while further destretching to correct for rubber-sheet seeing effects was performed following Shine et al (1994). We minimised the fringes in Stokes Q, U, and V by Fourier-filtering (following the procedure in Pietrow et al 2020) and increased the signal-to-noise ratio (S/N) in the Ca ii 8542 Å Stokes Q and U by applying the denoising neural network of Díaz Baso et al (2019).…”

Section: Observations and Reductionmentioning

confidence: 99%

Active region chromospheric magnetic fields

Vissers

Danilović

Zhu

et al. 2022

A&A

Self Cite

View full text Add to dashboard Cite

Context. A proper estimate of the chromospheric magnetic fields is thought to improve modelling of both active region and coronal mass ejection evolution. However, because the chromospheric field is not regularly obtained for sufficiently large fields of view, estimates thereof are commonly obtained through data-driven models or field extrapolations, based on photospheric boundary conditions alone and involving pre-processing that may reduce details and dynamic range in the magnetograms. Aims. We investigate the similarity between the chromospheric magnetic field that is directly inferred from observations and the field obtained from a magnetohydrostatic (MHS) extrapolation based on a high-resolution photospheric magnetogram. Methods. Based on Swedish 1-m Solar Telescope Fe I 6173 Å and Ca II 8542 Å observations of NOAA active region 12723, we employed the spatially regularised weak-field approximation (WFA) to derive the vector magnetic field in the chromosphere from Ca II, as well as non-local thermodynamic equilibrium (non-LTE) inversions of Fe I and Ca II to infer a model atmosphere for selected regions. Milne-Eddington inversions of Fe I serve as photospheric boundary conditions for the MHS model that delivers the three-dimensional field, gas pressure, and density self-consistently. Results. For the line-of-sight component, the MHS chromospheric field generally agrees with the non-LTE inversions and WFA, but tends to be weaker by 16% on average than these when larger in magnitude than 300 G. The observationally inferred transverse component is systematically stronger, up to an order of magnitude in magnetically weaker regions, but the qualitative distribution with height is similar to the MHS results. For either field component, the MHS chromospheric field lacks the fine structure derived from the inversions. Furthermore, the MHS model does not recover the magnetic imprint from a set of high fibrils connecting the main polarities. Conclusions. The MHS extrapolation and WFA provide a qualitatively similar chromospheric field, where the azimuth of the former is better aligned with Ca II 8542 Å fibrils than that of the WFA, especially outside strong-field concentrations. The amount of structure as well as the transverse field strengths are, however, underestimated by the MHS extrapolation. This underscores the importance of considering a chromospheric magnetic field constraint in data-driven modelling of active regions, particularly in the context of space weather predictions.

show abstract

Section: Observations and Reductionmentioning

confidence: 99%

Active region chromospheric magnetic fields

Vissers

Danilović

Zhu

et al. 2022

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…The physics and heating of plage regions have puzzled our community since the 70's. Three recent independent studies have attempted to infer the strength and stratification of the magnetic field in plage targets (Morosin et al 2020;Pietrow et al 2020; tions have further constrained this value to an average value of 5 km s −1 (da Silva Santos et al 2020). Whether these large values of microturbulence are related to turbulent velocity fields, sharp gradients along the line-of-sight induced by a hot magnetic canopy above the photosphere (Sanchez Almeida & Martinez Pillet 1994;Buehler et al 2015;Morosin et al 2020), answering this question is entangled with the enhanced values of radiative losses that have been reported in plage in comparison with the quiet Sun.…”

Section: Introductionmentioning

confidence: 99%

Spatio-temporal analysis of chromospheric heating in a plage region

Morosin,

Rodríguez,

Baso

et al. 2022

Preprint

View full text Add to dashboard Cite

Context. Our knowledge of the heating mechanisms that are at work in the chromosphere of plage regions remains highly unconstrained from observational studies. While many heating candidates have been proposed in theoretical studies, the exact contribution from each of them is still unknown. The problem is rather difficult because there is not direct way of estimating the heating terms from chromospheric observations. Aims. The purpose of our study is to estimate the chromospheric heating terms from a multi-line high spatial-resolution plage dataset, characterize their spatio-temporal distribution and set constraints on the heating processes that are at work in the chromosphere. Methods. We make use of non-local thermodynamical equilibrium (NLTE) inversions in order to infer a model of the photosphere and chromosphere of a plage dataset acquired with the Swedish 1-m Solar Telescope (SST). We use this model atmosphere to calculate the chromospheric radiative losses from the main chromospheric cooler from H i, Ca ii and Mg ii atoms. In this study, we approximate the chromospheric heating terms by the net radiative losses predicted by the inverted model. In order to make the analysis of timeseries over a large field-of-view (FOV) computationally tractable, we make use of a neural network which is trained from the inverted models of two non-consecutive time-steps. We have divided the chromosphere in three regions (lower, middle, upper) and analyzed how the distribution of the radiative losses is correlated with the physical parameters of the model. Results. In the lower chromosphere, the contribution from the Ca ii lines is dominant and predominantly located in the surroundings of the photospheric footpoints. In the upper chromosphere, the H i contribution is dominant. Radiative losses in the upper chromosphere form a relatively homogeneous patch that covers the entire plage region. The Mg ii also peaks in the upper chromosphere. Our time analysis shows that in all pixels, the net radiative losses can be split in a periodic component with an average amplitude of amp Q = 7.6 kW m −2 and a static (or very slowly evolving) component with a mean value of -26.1 kW m −2 . The period of the modulation present in the net radiative losses matches that of the line-of-sight velocity of the model. Conclusions. Our interpretation is that in the lower chromosphere, the radiative losses are tracing the sharp lower edge of the hot magnetic canopy that is formed above the photosphere, where the electric current is expected to be large. Therefore Ohmic current dissipation could explain the observed distribution. In the upper chromosphere, both the magnetic field and the distribution of net radiative losses are room-filling and relatively smooth, whereas the amplitude of the periodic component is largest. Our results suggest that acoustic wave heating may be responsible for one third of the energy deposition in the upper chromosphere, whereas other heating mechanisms must be responsible for the rest: turbulent Alfvén wave dissipation or...

show abstract

“…The Ca ii 8542 Å line has been one of the most studied lines in investigations of the magnetic, thermodynamic, and kinematic structure of the chromosphere (e.g., Pietarila et al 2007;Cauzzi et al 2008;de la Cruz Rodríguez et al 2012;Kleint 2012;Quintero Noda et al 2016;Kianfar et al 2020;Pietrow et al 2020). Spectropolarimetric observations of flares in the Ca ii 8542 Å line are now available from different groundbased instruments, for example the Interferometric Bidimensional Spectropolarimeter (BIS; Cavallini 2006) and the CRisp Imaging SpectroPolarimeter (CRISP; Scharmer et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Stratification of physical parameters in a C-class solar flare using multiline observations

Yadav

Baso

Rodríguez

et al. 2021

A&A

Self Cite

View full text Add to dashboard Cite

We present high-resolution and multiline observations of a C2-class solar flare (SOL2019-05-06T08:47), which occurred in NOAA AR 12740 on May 6, 2019. The rise, peak, and decay phases of the flare were recorded continuously and quasi-simultaneously in the Ca II K line with the CHROMIS instrument and in the Ca II 8542 Å and Fe I 6173 Å lines with the CRISP instrument at the Swedish 1 m Solar Telescope. The observations in the chromospheric Ca II lines exhibit intense brightening near the flare footpoints. At these locations, a nonlocal thermodynamic equilibrium inversion code was employed to infer the temperature, magnetic field, line-of-sight (LOS) velocity, and microturbulent velocity stratification in the flaring atmosphere. The temporal analysis of the inferred temperature at the flare footpoints shows that the flaring atmosphere from log τ500 ∼ −2.5 to −3.5 is heated up to 7 kK, whereas from log τ500 ∼ −3.5 to −5 the inferred temperature ranges between ∼7.5 kK and ∼11 kK. During the flare peak time, the LOS velocity shows both upflows and downflows around the flare footpoints in the upper chromosphere and lower chromosphere, respectively. Moreover, the temporal analysis of the LOS magnetic field at the flare points exhibits a maximum change of ∼600 G. After the flare, the LOS magnetic field decreases to the non-flaring value, exhibiting no permanent or step-wise change. The analysis of response functions to the temperature, LOS magnetic field, and velocity shows that the Ca II lines exhibit enhanced sensitivity to the deeper layers (i.e., log τ500 ∼ −3) of the flaring atmosphere, whereas for the non-flaring atmosphere they are mainly sensitive around log τ500 ∼ −4. We suggest that a fraction of the apparent increase in the LOS magnetic field at the flare footpoints may be due to the increase in the sensitivity of the Ca II 8542 Å line in the deeper layers, where the field strength is relatively strong. The rest may be due to magnetic field reconfiguration during the flare. In the photosphere, we do not notice significant changes in the physical parameters during the flare or non-flare times. Our observations illustrate that even a less intense C-class flare can heat the deeper layers of the solar chromosphere, mainly at the flare footpoints, without affecting the photosphere.

show abstract

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

Cited by 28 publications

References 69 publications

Active region chromospheric magnetic fields

Active region chromospheric magnetic fields

Spatio-temporal analysis of chromospheric heating in a plage region

Stratification of physical parameters in a C-class solar flare using multiline observations

Contact Info

Product

Resources

About

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

Cited by 28 publications

References 69 publications

Active region chromospheric magnetic fields

Active region chromospheric magnetic fields

Spatio-temporal analysis of chromospheric heating in a plage region

Stratification of physical parameters in a C-class solar flare using multiline observations

Contact Info

Product

Resources

About

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