Solar Magnetoconvection and Small-Scale Dynamo

Borrero, J. M.; Jafarzadeh, S.; Schüßler, M.; Solanki, S. K.

doi:10.1007/978-94-024-1521-6_10

Cited by 7 publications

(7 citation statements)

References 235 publications

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“…More recently, Danilovic et al (2016) found the distribution of IN field inclination to be quasi-isotropic by applying 2D inversions on Hinode data and comparing them with 3D magnetohydrodynamic simulations. For a detailed review on this, see Borrero et al (2015).…”

Section: Datamentioning

confidence: 99%

Estimation of the Magnetic Flux Emergence Rate in the Quiet Sun from Sunrise Data

Smitha

Anusha

Solanki

et al. 2017

ApJS

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Small-scale internetwork (IN) features are thought to be the major source of fresh magnetic flux in the quiet Sun. During its first science flight in 2009, the balloon-borne observatory Sunrise captured images of the magnetic fields in the quiet Sun at a high spatial resolution. Using these data we measure the rate at which the IN features bring magnetic flux to the solar surface. In a previous paper it was found that the lowest magnetic flux in small-scale features detected using the Sunrise observations is 9 × 10 14 Mx. This is nearly an order of magnitude smaller than the smallest fluxes of features detected in observations from Hinode satellite. In this paper, we compute the flux emergence rate (FER) by accounting for such small fluxes, which was not possible before Sunrise. By tracking the features with fluxes in the range 10 15 − 10 18 Mx, we measure an FER of 1100 Mx cm −2 day −1 . The smaller features with fluxes ≤ 10 16 Mx are found to be the dominant contributors to the solar magnetic flux. The FER found here is an order of magnitude higher than the rate from the Hinode, obtained with a similar feature tracking technique. A wider comparison with the literature shows, however, that the exact technique of determining the rate of the appearance of new flux can lead to results that differ by up to two orders of magnitude, even when applied to similar data. The causes of this discrepancy are discussed and first qualitative explanations proposed.

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Section: Datamentioning

confidence: 99%

Estimation of the Magnetic Flux Emergence Rate in the Quiet Sun from Sunrise Data

Smitha

Anusha

Solanki

et al. 2017

ApJS

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“…Thus, different magnetic environments on the solar surface, hosting a variety of magnetic features with a variety of properties (Borrero et al 2015), may represent different diffusivity behavior.…”

Section: Introductionmentioning

confidence: 99%

Kinematics of Magnetic Bright Features in the Solar Photosphere

Jafarzadeh¹,

Solanki²,

Cameron³

et al. 2017

ApJS

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Convective flows are known as the prime means of transporting magnetic fields on the solar surface. Thus, small magnetic structures are good tracers of turbulent flows. We study the migration and dispersal of magnetic bright features (MBFs) in intergranular areas observed at high spatial resolution with SUNRISE/IMaX. We describe the flux dispersal of individual MBFs as a diffusion process whose parameters are computed for various areas in the quiet-Sun and the vicinity of active regions from seeing-free data. We find that magnetic concentrations are best described as random walkers close to network areas (diffusion index, 1.0 g = ), travelers with constant speeds over a supergranule ( 1.9 2.0 g = -), and decelerating movers in the vicinity of flux emergence and/or within active regions ( 1.4 1.5 g = -). The three types of regions host MBFs with mean diffusion coefficients of 130 km 2 s −1 , 80-90 km 2 s −1 , and 25-70 km 2 s −1 , respectively. The MBFs in these three types of regions are found to display a distinct kinematic behavior at a confidence level in excess of 95%.

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“…The global dynamo refers to the physical processes that produce the cyclic regeneration of the large-scale solar magnetic field that underlies the solar cycle, including the manifestation of sunspots, faculae and network (Charbonneau, 2020). The small-scale turbulent dynamo or SSD denotes the interaction between solar convection and magnetic flux that yields the ubiquitous small-scale turbulent magnetic field on the solar surface, the so-termed internetwork magnetic field (Borrero et al, 2017). There is evidence to suggest that the internetwork magnetic field might also contribute to the magnetic network.…”

Section: The Least Active State Of the Sunmentioning

confidence: 99%

The Dimmest State of the Sun

Yeo

Solanki

Krivova

et al. 2020

Geophysical Research Letters

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How the solar electromagnetic energy entering the Earth's atmosphere varied since preindustrial times is an important consideration in the climate change debate. Detrimental to this debate, estimates of the change in total solar irradiance (TSI) since the Maunder minimum, an extended period of weak solar activity preceding the industrial revolution, differ markedly, ranging from a drop of 0.75 W m −2 to a rise of 6.3 W m −2. Consequently, the exact contribution by solar forcing to the rise in global temperatures over the past centuries remains inconclusive. Adopting a novel approach based on state-of-the-art solar imagery and numerical simulations, we establish the TSI level of the Sun when it is in its least-active state to be 2.0 ± 0.7 W m −2 below the 2019 level. This means TSI could not have risen since the Maunder minimum by more than this amount, thus restricting the possible role of solar forcing in global warming. Plain Language Summary How the amount of energy the Earth receives from the Sun varied since preindustrial times is an important consideration in the climate change debate. Detrimental to this debate, it is not known whether the Sun grew brighter or dimmer since the 16th century, and by how much. As a consequence, the exact contribution by fluctuations in the brightness of the Sun to the rise in global temperatures over the past centuries remains controversial. It is established that the Sun was particularly inactive over much of the 16th century. Adopting a novel approach based on state-of-the-art solar imagery and computer models, we determined the brightness of the Sun when it is in its least-active state possible. This places a strict limit on how much the Sun could have grown brighter since the lull in solar activity over the 16th century, restricting the possible role the Sun could have played in global warming. Since the reliable measurement of solar irradiance only started in 1978 (Kopp, 2014), climate simulations rely on models of solar irradiance variability to provide the requisite historical solar forcing input. Except at RESEARCH LETTER

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Solar Magnetoconvection and Small-Scale Dynamo

Cited by 7 publications

References 235 publications

Estimation of the Magnetic Flux Emergence Rate in the Quiet Sun from Sunrise Data

Estimation of the Magnetic Flux Emergence Rate in the Quiet Sun from Sunrise Data

Kinematics of Magnetic Bright Features in the Solar Photosphere

The Dimmest State of the Sun

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