Simultaneous Visible and Infrared Spectropolarimetry of a Solar Internetwork Region

Alméida, J. Sánchez; Cerdeña, I. Domínguez; Kneer, F.

doi:10.1086/379969

Cited by 45 publications

(4 citation statements)

References 16 publications

(22 reference statements)

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“…The ME inversions of the Fe i 630 nm lines carried out by Sigwarth et al (1999) and Sánchez Almeida et al (2003a) also delivered kG fields. This remains an unsolved problem, but we note that it is possible that they were biased by the modest angular resolution of the observations, since ME inversions seem to be adequate to analyze high resolution data (Orozco Suárez et al 2007a).…”

Section: Internetwork Fields Are Weak For the Most Partmentioning

confidence: 87%

Quiet Sun magnetic fields: an observational view

Rubio

Suárez

2019

Living Rev Sol Phys

119

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The quiet Sun is the region of the solar surface outside of sunspots, pores, and plages. In continuum intensity it appears dominated by granular convection. However, in polarized light the quiet Sun exhibits impressive magnetic activity on a broad range of scales, from the 30,000 km of supergranular cells down to the smallest magnetic features of about 100 km resolvable with current instruments. Quiet Sun fields are observed to evolve in a coherent way, interacting with each other as they are advected by the horizontal photospheric flows. They appear and disappear over surprisingly short time scales, bringing large amounts of magnetic flux to the solar surface. For this reason they may be important contributors to the heating of the chromosphere. Peering into such fields is difficult because of the weak signals they produce, which are easily affected, and even completely hidden, by photon noise. Thus, their evolution and nature remain largely unknown. In recent years the situation has improved thanks to the advent of high-resolution, high-sensitivity spectropolarimetric measurements and the application of state-of-the-art Zeeman and Hanle effect diagnostics. Here we review this important aspect of solar magnetism, paying special attention to the techniques used to observe and characterize the fields, their evolution on the solar surface, and their physical properties as revealed by the most recent analyses. We identify the main open questions that need to be addressed in the future and offer some ideas on how to solve them.

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Section: Internetwork Fields Are Weak For the Most Partmentioning

confidence: 87%

Quiet Sun magnetic fields: an observational view

Rubio

Suárez

2019

Living Rev Sol Phys

119

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“…This part is almost certainly magnetic, but with properties that remain elusive to our observation because of its complex magnetic topology that cancels Zeeman signals, because of the low field strengths, or both. Sánchez Almeida et al (2003) andDomínguez Cerdeña et al (2006a) show how part of these hidden fields can be revealed through MISMA inversion by analyzing Fe i infra-red lines. Even weaker fields can be inferred and diagnosed via Hanle effect (e.g., Faurobert-Scholl 1994;Bommier et al 2005).…”

Section: Discussionmentioning

confidence: 99%

Interpretation ofHINODESOT/SP asymmetric Stokes profiles observed in the quiet Sun network and internetwork

Viticchiè¹,

Alméida²,

Moro³

et al. 2010

A&A

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Stokes profiles emerging from the magnetized solar photosphere and observed by SOT/SP aboard the HINODE satellite exhibit a variety of complex shapes. These are indicative of unresolved magnetic structures that have been overlooked in the inversion analyses performed so far. Here we present the first interpretation of the Stokes profile asymmetries measured in the Fe i 630 nm lines by SOT/SP, in both quiet Sun internetwork (IN) and network regions. The inversion is carried out based on the hypothesis of MIcro-Structured Magnetized Atmosphere (MISMA), where the unresolved structure is assumed to be optically thin. We analyze a 29.52 × 31.70 subfield carefully selected to be representative of the properties of a 302 × 162 quiet Sun field-of-view (FOV) at the disk center. The inversion code is able to reproduce the observed asymmetries in a very satisfactory way, including 35% of the inverted profiles with large asymmetries. The inversion code interprets 25% of inverted profiles as emerging from pixels in which both positive and negative polarities coexist. These pixels are located in either frontiers between opposite polarity patches or very quiet regions. The kG field strengths are found at the base of the photosphere in both network and IN regions; in the case of the latter, both kG fields and hG fields are admixed. When considering the magnetic properties of the mid photosphere, most kG fields do not exist, and the statistics is dominated by hG fields. According to the magnetic filling factors derived from the inversion, we constrain the magnetic field of only 4.5% of the analyzed photosphere (and this percentage reduces to 1.3% when considering all pixels, including those with low polarization that have not been analyzed). The properties of the rest of the plasma imply that weak fields do not contribute to the detected polarization signals. The average flux densities derived in the full subfield and IN regions are higher than those derived from the same dataset by Milne-Eddington (ME) inversion. We detect large asymmetries in the HINODE SOT/SP polarization profiles. These are not negligible in quiet Sun data. The MISMA inversion code reproduces them in a satisfactory way, and provides a statistical description of the magnetized IN and network which partly differs and complements the results obtained so far. The importance of having a complete interpretation of the line profile shapes is therefore clearly evident.

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“…Results from the near infrared Fe  lines at 1.56 microns usually lead to the conclusion that most of the mag-netic fields in the internetwork are in the form of weak fields (see Lin, 1995;Lin & Rimmele, 1999;Khomenko et al, 2003). This result is confirmed by Mart ínez González et al (2006b) but contradicted by Sánchez Almeida et al (2003) and Dom ínguez Cerdeña et al (2006). These last three works analyze simultaneous 1.5 µm and 630 nm observations.…”

Section: Introductionmentioning

confidence: 90%

On the validity of the 630 nm Fe I lines for magnetometry of the internetwork quiet Sun

González¹,

Collados²,

Cobo³

2006

A&A

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Aims. The purpose of this work is to analyze the reliability of the magnetic field strengths inferred from the 630 nm pair of Fe i lines in internetwork quiet Sun regions. Methods. Some numerical experiments have been performed that demonstrate the inability of these lines to recover the magnetic field strength in such low flux solar regions. Results. It is shown how different model atmospheres, with magnetic field strengths ranging from a few hundred Gauss to kiloGauss, give rise to Stokes profiles that cannot be distinguished. The reasons for this degeneracy are discussed.

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Simultaneous Visible and Infrared Spectropolarimetry of a Solar Internetwork Region

Cited by 45 publications

References 16 publications

Quiet Sun magnetic fields: an observational view

Quiet Sun magnetic fields: an observational view

Interpretation ofHINODESOT/SP asymmetric Stokes profiles observed in the quiet Sun network and internetwork

On the validity of the 630 nm Fe I lines for magnetometry of the internetwork quiet Sun

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