Small-Scale Solar Magnetic Fields

Wijn, A. G. de; Stenflo, J. O.; Solanki, S. K.; Tsuneta, S.

doi:10.1007/978-1-4419-0239-9_16

Cited by 12 publications

(13 citation statements)

References 144 publications

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“…Both of the positive and negative polarities with smallest sizes, known as "patches", are observable in the line-of-sight magnetograms. These magnetic field concentrations are often consistent with appearing bright points in G band and CaII H lines (Otsuji et al 2007, de Wijn et al 2009. The size and flux of magnetic patches are ranged from 10 14 to 10 16 cm 2 and 10 17 to 10 19 Mx, respectively (e.g., Stenflo 1973, Hagenaar et al 2003, Priest 2014.…”

Section: Introductionsupporting

confidence: 54%

“…The solar surface is ubiquitously covered by the magnetic elements in which their flux and size distributions follow scale-free behavior (e.g., Parnell et al 2009, Javaherian et al 2017. The mag-netic elements emerged in pairs with opposite polarities (Lorrain et al 2006, de Wijn et al 2009. Both of the positive and negative polarities with smallest sizes, known as "patches", are observable in the line-of-sight magnetograms.…”

Section: Introductionmentioning

confidence: 99%

“…The size and flux of magnetic patches are ranged from 10 14 to 10 16 cm 2 and 10 17 to 10 19 Mx, respectively (e.g., Stenflo 1973, Hagenaar et al 2003, Priest 2014. The patches' size increases with increasing latitude, and many of patches tend to have appeared as isolated ones in the polar region with high order of magnetic strength about one kG (de Wijn et al 2009). To understand the underlying process of magnetic elements, many statistical works were done.…”

Section: Introductionmentioning

confidence: 99%

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Empirical Scaling Relations for the Photospheric Magnetic Elements of the Flaring and Non-Flaring Active Regions

Moradhaseli,

Javaherian,

Fathalian

et al. 2021

Preprint

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Here, we analyzed magnetic elements of the solar active regions (ARs) observed in the line-of-sight magnetograms (the 6173 Å Fe I line) recorded with the Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager (HMI). The Yet Another Feature Tracking Algorithm (YAFTA) was employed to extract the statistical properties of these features (e.g. filling factor, magnetic flux, and lifetime) within the areas of 180 ′′ × 180 ′′ inside the flaring AR (NOAA 12443) and the non-flaring AR (NOAA 12446) for 3 to 5 November 2015 and for 4 to 6 November 2015, respectively. The mean filling factor of polarities was obtained to be about 0.49 for the flaring AR; this value was 0.08 for the non-flaring AR. Time series of the filling factors of the negative and positive polarities for the flaring AR showed anti-correlation (with the Pearson value of -0.80); while for the non-flaring AR, there was the strong positive correlation (with the Pearson value of 0.95). A power-law function was fitted to the frequency distributions of flux (F), size (S), and lifetime (T). Power exponents of the distributions of flux, size, and lifetime for the flaring AR were obtained to be about -2.36, -3.11, and -1.70, respectively; these values of exponents for the non-flaring AR were found to be about -2.53, -3.42, and -1.61, respectively. The code detected a magnetic element with the maximum flux of 23.54 × 10 20 Mx, and the maximum value of the size was found to be about 300 Mm 2 . The most long-lived patch in the flaring AR was belonged to an element with the lifetime of 2208 minutes. It was revealed that S, T, and F for patches in the flaring AR follow empirical scaling relations as S ∝ F 0.66 , S ∝ T 0.32 , and F ∝ T 0.48 , respectively; For appeared patches in the non-flaring AR, these relations were obtained as S ∝ F 0.64 , S ∝ T 0.23 and F ∝ T 0.37 , respectively. The comparisons indicated that values of correlations between parameters of F and T, and also, S and T for the flaring AR, are more than those of the non-flaring AR, and the quite-Sun (QS). The scaling law relation between the flux growth rate of positive polarities and their size revealed a strong correlation of more than 0.7 in both ARs. Sun: flares -Sun: photosphere -Sun: magnetic fields -methods: data analysis -methods: statistical -techniques: miscellaneous

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Section: Introductionsupporting

confidence: 54%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Empirical Scaling Relations for the Photospheric Magnetic Elements of the Flaring and Non-Flaring Active Regions

Moradhaseli,

Javaherian,

Fathalian

et al. 2021

Preprint

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“…The energy is transported into the corona via magnetic structures in the lower atmosphere. In both active and quiet areas of the solar photosphere the magnetic field is highly fragmented (Stenflo 1973(Stenflo , 1989Solanki 1993;Schrijver et al 1998;Berger & Title 2001;Priest et al 2002;Abramenko & Longcope 2005;DeWijn et al 2009;Gonzalez et al 2012). The field is concentrated into discrete flux elements with kilogauss field strengths and widths ranging from 100 km for the smallest observable elements to 3 × 10 4 km for large sunspots.…”

Section: Introductionmentioning

confidence: 99%

On the Relationship Between Photospheric Footpoint Motions and Coronal Heating in Solar Active Regions

Ballegooijen

Asgari-Targhi

Berger

2014

ApJ

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Coronal heating theories can be classified as either direct current (DC) or alternating current (AC) mechanisms, depending on whether the coronal magnetic field responds quasi-statically or dynamically to the photospheric footpoint motions. In this paper we investigate whether photospheric footpoint motions with velocities of 1-2 km s −1 can heat the corona in active regions, and whether the corona responds quasi-statically or dynamically to such motions (DC versus AC heating). We construct three-dimensional magnetohydrodynamic models for the Alfvén waves and quasi-static perturbations generated within a coronal loop. We find that in models where the effects of the lower atmosphere are neglected, the corona responds quasi-statically to the footpoint motions (DC heating), but the energy flux into the corona is too low compared to observational requirements. In more realistic models that include the lower atmosphere, the corona responds more dynamically to the footpoint motions (AC heating) and the predicted heating rates due to Alfvén wave turbulence are sufficient to explain the observed hot loops. The higher heating rates are due to the amplification of Alfvén waves in the lower atmosphere. We conclude that magnetic braiding is a highly dynamic process.

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“…Well established theoretical models produce bipolar features, rather than unipolar features. In those models IN fields are generated by small-scale surface dynamo action (Cattaneo 1999;Cattaneo & Hughes 2001;Vögler & Schüssler 2007;Danilovic et al 2010a;Rempel 2014), flux recycling from decayed active regions (e.g., Ploner et al 2001;de Wijn et al 2005), flux emergence from subphotospheric layers (de Wijn et al 2009) similar to ephemeral regions (Harvey & Martin 1973;Harvey et al 1975;Hagenaar 2001), and shallow recir-culation in granular convection (Rempel 2018;Fischer et al 2020).…”

Section: Introductionmentioning

confidence: 99%

The solar internetwork. III. Unipolar versus bipolar flux appearance

Gošić,

Rubio,

Cheung

et al. 2021

Preprint

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Small-scale internetwork (IN) magnetic fields are considered to be the main building blocks of the quiet Sun magnetism. For this reason, it is crucial to understand how they appear on the solar surface. Here, we employ a high-resolution, high-sensitivity, long-duration Hinode/NFI magnetogram sequence to analyze the appearance modes and spatio-temporal evolution of individual IN magnetic elements inside a supergranular cell at the disk center. From identification of flux patches and magnetofrictional simulations, we show that there are two distinct populations of IN flux concentrations: unipolar and bipolar features. Bipolar features tend to be bigger and stronger than unipolar features. They also live longer and carry more flux per feature. Both types of flux concentrations appear uniformly over the solar surface. However, we argue that bipolar features truly represent the emergence of new flux on the solar surface, while unipolar features seem to be formed by coalescence of background flux. Magnetic bipoles appear at a faster rate than unipolar features (68 as opposed to 55 Mx cm −2 day −1 ), and provide about 70% of the total instantaneous IN flux detected in the interior of the supergranule.

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Small-Scale Solar Magnetic Fields

Cited by 12 publications

References 144 publications

Empirical Scaling Relations for the Photospheric Magnetic Elements of the Flaring and Non-Flaring Active Regions

Empirical Scaling Relations for the Photospheric Magnetic Elements of the Flaring and Non-Flaring Active Regions

On the Relationship Between Photospheric Footpoint Motions and Coronal Heating in Solar Active Regions

The solar internetwork. III. Unipolar versus bipolar flux appearance

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