Quiet-Sun Internetwork Magnetic Fields from the Inversion of
                    <i>Hinode</i>
                    Measurements

Suárez, D. Orozco; Rubio, L. R. Bellot; Iniesta, J. C. del Toro; Tsuneta, S.; Lites, B. W.; Ichimoto, Kiyoshi; Katsukawa, Y.; Nagata, Shinji; Shimizu, Toshifumi; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title, A. M.

doi:10.1086/524139

Cited by 194 publications

(211 citation statements)

References 16 publications

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“…In this review we will describe the Hinode results in some detail, before relating them to the more long-term results based on synoptic observations of the line-of-sight field component. These observations revealed a unipolar but highly complex and non-uniform flux distribution, containing ubiquitous fields of greater strength (> 1 kG) than many had previously expected, though bundles of kilogauss field had previously been observed at high latitudes (Homann et al, 1997;Okunev and Kneer, 2004;Blanco Rodríguez et al, 2007) as well as in the low-latitude quiet-Sun photosphere (Orozco Suárez et al, 2007).…”

Section: Introductionmentioning

confidence: 67%

“…However, because the distribution of the inclination (zenith) angle of the magnetic vector with respect to the local normal has two peaks, one at the local vertical direction and the other at the local horizontal direction (Orozco Suárez et al, 2007), it is possible to determine the inclination angle close to the solar limb without the usual 180 ∘ azimuth ambiguity (Ito et al, 2010). Figure 2 shows a map of the continuum brightness distribution over the domain corresponding to the portion of Figure 1 poleward of 80 ∘ .…”

Section: High-resolution Observations Of Polar Fieldsmentioning

confidence: 99%

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Solar Magnetism in the Polar Regions

Petrie

2015

Living Rev. Sol. Phys.

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This review describes observations of the polar magnetic fields, models for the cyclical formation and decay of these fields, and evidence of their great influence in the solar atmosphere. The polar field distribution dominates the global structure of the corona over most of the solar cycle, supplies the bulk of the interplanetary magnetic field via the polar coronal holes, and is believed to provide the seed for the creation of the activity cycle that follows. A broad observational knowledge and theoretical understanding of the polar fields is therefore an essential step towards a global view of solar and heliospheric magnetic fields. Analyses of both high-resolution and long-term synoptic observations of the polar fields are summarized. Models of global flux transport are reviewed, from the initial phenomenological and kinematic models of Babcock and Leighton to present-day attempts to produce time-dependent maps of the surface magnetic field and to explain polar field variations, including the weakness of the cycle 23 polar fields. The relevance of the polar fields to solar physics extends far beyond the surface layers from which the magnetic field measurements usually derive. As well as discussing the polar fields' role in the interior as seed fields for new solar cycles, the review follows their influence outward to the corona and heliosphere. The global coronal magnetic structure is determined by the surface magnetic flux distribution, and is dominated on large scales by the polar fields. We discuss the observed effects of the polar fields on the coronal hole structure, and the solar wind and ejections that travel through the atmosphere. The review concludes by identifying gaps in our knowledge, and by pointing out possible future sources of improved observational information and theoretical understanding of these fields. Article RevisionsLiving Reviews supports two ways of keeping its articles up-to-date:Fast-track revision. A fast-track revision provides the author with the opportunity to add short notices of current research results, trends and developments, or important publications to the article. A fast-track revision is refereed by the responsible subject editor. If an article has undergone a fast-track revision, a summary of changes will be listed here.Major update. A major update will include substantial changes and additions and is subject to full external refereeing. It is published with a new publication number.For detailed documentation of an article's evolution, please refer to the history document of the article's online version at http://dx

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Section: Introductionmentioning

confidence: 67%

Section: High-resolution Observations Of Polar Fieldsmentioning

confidence: 99%

Solar Magnetism in the Polar Regions

Petrie

2015

Living Rev. Sol. Phys.

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“…In these data, hG were found in the internetwork (e.g. Orozco Suárez et al 2007). Today, most of the community agrees that magnetic fields in the very quiet Sun are in the hG regime or even weaker.…”

Section: Introductionmentioning

confidence: 79%

Inference of magnetic fields in the very quiet Sun

González

Yabar

Lagg

et al. 2016

A&A

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Context. Over the past 20 yr, the quietest areas of the solar surface have revealed a weak but extremely dynamic magnetism occurring at small scales (<500 km), which may provide an important contribution to the dynamics and energetics of the outer layers of the atmosphere. Understanding this magnetism requires the inference of physical quantities from high-sensitivity spectro-polarimetric data with high spatio-temporal resolution. Aims. We present high-precision spectro-polarimetric data with high spatial resolution (0.4 ) of the very quiet Sun at 1.56 µm obtained with the GREGOR telescope to shed some light on this complex magnetism. Methods. We used inversion techniques in two main approaches. First, we assumed that the observed profiles can be reproduced with a constant magnetic field atmosphere embedded in a field-free medium. Second, we assumed that the resolution element has a substructure with either two constant magnetic atmospheres or a single magnetic atmosphere with gradients of the physical quantities along the optical depth, both coexisting with a global stray-light component. Results. Half of our observed quiet-Sun region is better explained by magnetic substructure within the resolution element. However, we cannot distinguish whether this substructure comes from gradients of the physical parameters along the line of sight or from horizontal gradients (across the surface). In these pixels, a model with two magnetic components is preferred, and we find two distinct magnetic field populations. The population with the larger filling factor has very weak (∼150 G) horizontal fields similar to those obtained in previous works. We demonstrate that the field vector of this population is not constrained by the observations, given the spatial resolution and polarimetric accuracy of our data. The topology of the other component with the smaller filling factor is constrained by the observations for field strengths above 250 G: we infer hG fields with inclinations and azimuth values compatible with an isotropic distribution. The filling factors are typically below 30%. We also find that the flux of the two polarities is not balanced. From the other half of the observed quiet-Sun area ∼50% are two-lobed Stokes V profiles, meaning that 23% of the field of view can be adequately explained with a single constant magnetic field embedded in a non-magnetic atmosphere. The magnetic field vector and filling factor are reliable inferred in only 50% based on the regular profiles. Therefore, 12% of the field of view harbour hG fields with filling factors typically below 30%. At our present spatial resolution, 70% of the pixels apparently are non-magnetised.

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“…Thus through analyses of infrared data obtained with TIP on the German VTT Khomenko et al (2003) find a broad range of inclination angles but with preference for more vertical fields, Martínez González et al (2008a) conclude that the distribution is isotropic, while Beck & Rezaei (2009) find fields of both small and large inclinations, and conclude that the more vertical fields carry twice as much flux as the strongly inclined fields. In contrast, Orozco Suárez et al (2007) and Lites et al (2008) find a very strong predominance of horizontal fields from analysis of Hinode SOT/SP quiet-Sun data using the 6301-6302 Å line pair, while Asensio Ramos (2009) concludes from the same Hinode data that the angular distribution is quasi-isotropic.…”

Section: Introductionmentioning

confidence: 90%

Distribution functions for magnetic fields on the quiet Sun

Stenflo

2010

A&A

144

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The statistical properties of the highly structured magnetic field of the quiet Sun are best described in terms of distribution functions, in particular the probability density functions (PDF) for the flux densities and the angular distribution for the orientations of the field vector. They are needed to test the validity of various MHD simulations, but past determinations have led to contradictory results. A main reason for these difficulties lies in the circumstance that the magnetic structuring continues on scales that are much smaller than the telescope resolution, and that this structuring strongly affects the quantities averaged over each pixel due to the non-linear relation between polarization and magnetic field. Here we use a Hinode SOT/SP data set for the disk center of the quiet Sun to explore the complex behavior of the polarized 6301-6302 Å line system and identify the observables that allow the most robust determinations of inclination angles and flux densities. These observables are then used to derive the empirical distribution functions. Our Stokes V line ratio analysis leads us to an unexpected discovery: a magnetic dichotomy with two distinct populations, representing strong (kG) and weak fields. This can be understood in terms of the convective collapse mechanism, which makes the Sun's magnetic flux end up in two states: collapsed and uncollapsed. With the linear-to-circular polarization ratio as a robust observable for the inclination angles, we find that the angular distribution is extremely peaked around the vertical direction for the largest flux densities, but gradually broadens as we go to smaller flux densities, to become asymptotically isotropic at zero flux density. The PDF for the vertical flux density, after accounting for the smearing effect of measurement noise, is found to have an extremely narrow core peak centered at zero flux density, which can be analytically represented by a stretched exponential. The PDF wings are extended and decline quadratically. The PDFs for the horizontal and total flux densities have a similar behavior. In particular we demonstrate that earlier claims that the PDF for the total flux density increases from small values at zero flux density to have a maximum significantly shifted from zero is an artefact of measurement noise.

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Quiet-Sun Internetwork Magnetic Fields from the Inversion of Hinode Measurements

Cited by 194 publications

References 16 publications

Solar Magnetism in the Polar Regions

Solar Magnetism in the Polar Regions

Inference of magnetic fields in the very quiet Sun

Distribution functions for magnetic fields on the quiet Sun

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