The solar magnetic field

Solanki, S. K.; Inhester, B.; Schüßler, M.

doi:10.1088/0034-4885/69/3/r02

Cited by 278 publications

(249 citation statements)

References 601 publications

(827 reference statements)

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“…The idea is illustrated in Figure 8: Thinner flux tubes (radius smaller than 500 km) are effectively coupled to the motion of the surrounding plasma by the drag force, while larger tubes (radius larger than 500 km) can move relative to the surrounding plasma owing to the action of the magnetic force, similar to a flexible solid body immersed in a fluid (Solanki, Inhester, and Schüssler, 2006). This result was expected, but is still nice to see in the simulations.…”

Section: Scattering Of Tubesmentioning

confidence: 78%

“…Unfortunately with observations at a single height they were unable to identify what mixture of m = 0, axisymmetric sausage-modes, and m = 1, kinkmodes, they were observing. Theoretical studies of the interaction of flux tubes and waves have been performed in the past, for example Roberts and Webb (1979), Wilson (1980), Spruit (1981), Spruit (1982), Bogdan and Knölker (1989), Solanki (1993), Bogdan et al (1996), Hasan and Kalkofen (1999), Tirry (2000), Gizon, Hanasoge, and Birch (2006), Jain and Gordovskyy (2008), Hanasoge et al (2008), Hanasoge and Cally (2009). It is now well established that slender magnetic flux tubes permit the propagation of the two basic types of magnetohydrodynamic waves: The longitudinal tube waves (sausage modes) with azimuthal wave number m = 0, which are axisymmetric, excited by pressure fluctuations.…”

Section: Introductionmentioning

confidence: 99%

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3D Numerical Simulations of f-Mode Propagation Through Magnetic Flux Tubes

et al. 2010

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Three-dimensional numerical simulations have been used to study the scattering of a surface-gravity wave packet by vertical magnetic flux tubes, with radii from 200 km to 3 Mm, embedded in stratified polytropic atmosphere. The scattered wave was found to consist primarily of m = 0 (axisymmetric) and m = 1 modes. It was found that the ratio of the amplitude of these two modes is strongly dependant on the radius of the flux tube: The kink mode is the dominant mode excited in tubes with a small radius while the sausage mode is dominant for large tubes. Simulations of this type provide a simple, efficient and robust way to start understanding the seismic signature of flux tubes, which have recently began to be observed.

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Section: Scattering Of Tubesmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

3D Numerical Simulations of f-Mode Propagation Through Magnetic Flux Tubes

et al. 2010

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“…This effect is expected to be stronger for the solar-disk component than the IC component because of the much closer approach to the Sun for the parent cosmic rays. In addition, magnetic fields in the solar atmosphere [14][15][16] affect the solar-disk component. Seckel et al [10] (denoted as SSG1991 in the following) showed that solar atmospheric magnetic fields could boost gamma-ray production through the magnetic reflection of the primary cosmic rays or their showers out of the Sun.…”

Section: Introductionmentioning

confidence: 99%

First observation of time variation in the solar-disk gamma-ray flux with Fermi

Beacom

Peter

et al. 2016

Phys. Rev. D

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The solar disk is a bright gamma-ray source. Surprisingly, its flux is about one order of magnitude higher than predicted. As a first step toward understanding the physical origin of this discrepancy, we perform a new analysis in 1-100 GeV using 6 years of public Fermi-LAT data. Compared to the previous analysis by the Fermi Collaboration, who analyzed 1.5 years of data and detected the solar disk in 0.1-10 GeV, we find two new and significant results: 1. In the 1-10 GeV flux (detected at > 5σ), we discover a significant time variation that anticorrelates with solar activity. 2. We detect gamma rays in 10-30 GeV at > 5σ, and in 30-100 GeV at > 2σ. The time variation strongly indicates that solar-disk gamma rays are induced by cosmic rays and that solar atmospheric magnetic fields play an important role. Our results provide essential clues for understanding the underlying gamma-ray production processes, which may allow new probes of solar atmospheric magnetic fields, cosmic rays in the solar system, and possible new physics. Finally, we show that the Sun is a promising new target for ground-based TeV gamma-ray telescopes such as HAWC and LHAASO.PACS numbers: 95.85. Pw, 13.85.Qk, 96.50.Vg

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“…For further reading, we want to draw the reader's attention to classical overviews of the theoretical aspects of solar magnetism by Parker (1979) and Priest (1982, as well as previous descriptions dedicated to aspects of the magnetic properties of the Sun's magnetic field by Solanki et al (2006). We also refer to Schrijver and Zwaan (2000) for a comparative work on the magnetic activity of the Sun and other stars.…”

Section: Introductionmentioning

confidence: 99%

The magnetic field in the solar atmosphere

Wiegelmann

Thalmann

Solanki

2014

Astron Astrophys Rev

183

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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The solar magnetic field

Cited by 278 publications

References 601 publications

3D Numerical Simulations of f-Mode Propagation Through Magnetic Flux Tubes

3D Numerical Simulations of f-Mode Propagation Through Magnetic Flux Tubes

First observation of time variation in the solar-disk gamma-ray flux with Fermi

The magnetic field in the solar atmosphere

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