Low-lying magnetic loops in the solar internetwork

González, M. J. Martínez; Collados, M.; Cobo, B. Ruiz; Solanki, S. K.

doi:10.1051/0004-6361:20077505

Cited by 72 publications

(74 citation statements)

References 16 publications

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“…Such fields, partly seen in the internetwork regions by Hinode (e.g. Lites et al 2007), are very likely small loops (Centeno et al 2007;Martínez González et al 2007) and may be due to a local dynamo (Vögler & Schüssler 2007;Schüssler & Vögler 2008). It is unclear if such low-lying loops really influence the structure of the higher-lying chromosphere.…”

Section: Discussionmentioning

confidence: 99%

The relationship between chromospheric emissions and magnetic field strength

Loukitcheva

Solanki

White

2009

A&A

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Aims. We analyze observational data from 4 instruments to study the correlations between chromospheric emission, spanning the heights from the temperature minimum region to the middle chromosphere, and photospheric magnetic field. Methods. The data consist of radio images at 3.5 mm from the Berkeley-Illinois-Maryland Array (BIMA), UV images at 1600 Å from TRACE, Ca ii K-line filtergrams from BBSO, and MDI/SOHO longitudinal photospheric magnetograms. For the first time interferometric millimeter data with the highest currently available resolution are included in such an analysis. We determine various parameters of the intensity maps and correlate the intensities with each other and with the magnetic field. Results. The chromospheric diagnostics studied here show a pronounced similarity in their brightness structures and map out the underlying photospheric magnetic field relatively well. We find a power law to be a good representation of the relationship between photospheric magnetic field and emission from chromospheric diagnostics at all wavelengths. The dependence of chromospheric brightness on magnetic field is found to be different for network and internetwork regions.

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Section: Discussionmentioning

confidence: 99%

The relationship between chromospheric emissions and magnetic field strength

Loukitcheva

Solanki

White

2009

A&A

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“…presented in Martínez González et al 2007). The present emergence rate is almost seven times higher than the rate inferred from IMaX data using the Fe i visible line at 525 nm at ∼0.15…”

Section: Observationsmentioning

confidence: 99%

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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“…Below that we generally speak of "ephemeral regions" (10 18 to 10 20 Mx). Even smaller are the smallest so far resolved bipolar features, the internetwork magnetic loops (Martínez González et al 2007;Centeno et al 2007;Martínez González and Bellot Rubio 2009;Danilovic et al 2010a) which emerge throughout the QS (although preferring a meso-scale pattern). They have fluxes of roughly 10 16 to 10 17 Mx (Lin and Rimmele 1999) and display in general weak equipartition (that is, the magnetic energy density is similar to the kinetic energy density of the convective flows) intrinsic fields.…”

Section: Magnetic Flux Emergencementioning

confidence: 99%

“…Martínez González et al (2007), using data from VTT, found low-lying photospheric magnetic loops connecting about 10 to 20 % of the visible magnetic flux of opposite polarity. Note that emerging small-scale loops are observed in the form of newly detected horizontal fields well before vertical flux is detected (see Centeno et al 2007, for a corresponding study based on Hinode/SOT-SP data).…”

Section: Photospheric Quiet-sun Loopsmentioning

confidence: 99%

“…Obviously, Aly's condition is not fulfilled in the internetwork photosphere where the horizontal field is on average much stronger than the vertical field, which has important implications for the reliability of force-free magnetic field reconstructions in the QS. The fact that these fields are definitely far from being force-free in the photosphere and that most of the weak (nearly) horizontal fields are the tops of very short and low-lying loops (Martínez González et al 2007;Centeno et al 2007;Martínez González and Bellot Rubio 2009;Danilovic et al 2010a) which do not reach up to layers where the field is closer to being force-free, the impact of the plasma on the field cannot be neglected.…”

Section: Force-freeness Of Quiet-sun Magnetic Fieldsmentioning

confidence: 99%

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The magnetic field in the solar atmosphere

Wiegelmann

Thalmann

Solanki

2014

Astron Astrophys Rev

182

125

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This publication provides an overview of magnetic fields in the solar atmosphere with the focus lying on the corona. The solar magnetic field couples the solar interior with the visible surface of the Sun and with its atmosphere. It is also responsible for all solar activity in its numerous manifestations. Thus, dynamic phenomena such as coronal mass ejections and flares are magnetically driven. In addition, the field also plays a crucial role in heating the solar chromosphere and corona as well as in accelerating the solar wind. Our main emphasis is the magnetic field in the upper solar atmosphere so that photospheric and chromospheric magnetic structures are mainly discussed where relevant for higher solar layers. Also, the discussion of the solar atmosphere and activity is limited to those topics of direct relevance to the magnetic field. After giving a brief overview about the solar magnetic field in general and its global structure, we discuss in more detail the magnetic field in active regions, the quiet Sun and coronal holes.

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Low-lying magnetic loops in the solar internetwork

Cited by 72 publications

References 16 publications

The relationship between chromospheric emissions and magnetic field strength

The relationship between chromospheric emissions and magnetic field strength

Inference of magnetic fields in the very quiet Sun

The magnetic field in the solar atmosphere

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