Role of the background regimes towards the Solar Mean Magnetic Field (SMMF)

AbstractThe Solar Mean Magnetic Field (SMMF) is generally defined as the disc-averaged line-of-sight (LOS) magnetic field on the sun. The role of the active regions and the large-scale magnetic field structures (also called the background) has been debated over the past few decades to understand whether the origin of the SMMF is either due to the active regions or the background. We, in this paper have investigated contribution of sunspots, plages, networks and the background towards the variability of the SMMF using the datasets from the SDO-AIA & HMI, and found that 89% of the SMMF is due to the background whereas the remaining 11% originates from the active regions and the networks.

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Numerical Simulations of Large-scale Solar Magnetic Fields

Australian Journal of Physics ◽

10.1071/ph850999 ◽

1985 ◽

Vol 38 (6) ◽

pp. 999 ◽

Cited By ~ 24

Author(s):

CR DeVore ◽

NR Sheeley Jr ◽

JP Boris ◽

TR Young Jr ◽

KL Harvey

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

Large Scale ◽

Sunspot Cycle ◽

Active Regions ◽

The Sun ◽

Solar Magnetic Fields ◽

Field Patterns ◽

Large Scale Magnetic Field ◽

The Magnetic Field

We have solved numerically a transport equation which describes the evolution of the large-scale magnetic field of the Sun. Data derived from solar magnetic observations are used to initialize the computations and to account for the emergence of new magnetic flux during the sunspot cycle. Our objective is to assess the ability of the model to reproduce the observed evolution of the field patterns. We discuss recent results from simulations of individual active regions over a few solar rotations and of the magnetic field of the Sun over sunspot cycle 21.

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How to make the Sun look less like the Sun and more like a star?

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317003908 ◽

2016 ◽

Vol 12 (S328) ◽

pp. 237-239

Author(s):

A. A. Vidotto

Keyword(s):

Magnetic Field ◽

Large Scale ◽

Vector Fields ◽

Radial Component ◽

Field Vector ◽

Small Scale ◽

General Context ◽

The Sun ◽

Flux Transport ◽

Large Scale Magnetic Field

AbstractSynoptic maps of the vector magnetic field have routinely been made available from stellar observations and recently have started to be obtained for the solar photospheric field. Although solar magnetic maps show a multitude of details, stellar maps are limited to imaging large-scale fields only. In spite of their lower resolution, magnetic field imaging of solar-type stars allow us to put the Sun in a much more general context. However, direct comparison between stellar and solar magnetic maps are hampered by their dramatic differences in resolution. Here, I present the results of a method to filter out the small-scale component of vector fields, in such a way that comparison between solar and stellar (large-scale) magnetic field vector maps can be directly made. This approach extends the technique widely used to decompose the radial component of the solar magnetic field to the azimuthal and meridional components as well, and is entirely consistent with the description adopted in several stellar studies. This method can also be used to confront synoptic maps synthesised in numerical simulations of dynamo and magnetic flux transport studies to those derived from stellar observations.

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Reconstruction of Sun-as-Star Magnetic Field Structure and Evolution Using Filament Observations

International Astronomical Union Colloquium ◽

10.1017/s0252921100048156 ◽

1998 ◽

Vol 167 ◽

pp. 493-496

Author(s):

Dmitri I. Ponyavin

Keyword(s):

Magnetic Field ◽

Solar Cycle ◽

Large Scale ◽

Solar Magnetic Field ◽

Close Association ◽

Field Structure ◽

The Sun ◽

Magnetic Field Structure ◽

Large Scale Magnetic Field ◽

Field Organization

AbstractA technique is used to restore the magnetic field of the Sun viewed as star from the filament distribution seen on Hα photographs. For this purpose synoptic charts of the large-scale magnetic field reconstructed by the McIntosh method have been compared with the Sun-asstar solar magnetic field observed at Stanford. We have established a close association between the Sun-as-star magnetic field and the mean magnetic field inferred from synoptic magnetic field maps. A filtering technique was applied to find correlations between the Sun-as-star and large-scale magnetic field distributions during the course of a solar cycle. The correlations found were then used to restore the Sun-as-star magnetic field and its evolution in the late 1950s and 1960s, when such measurements of the field were not being made. A stackplot display of the inferred data reveals large-scale magnetic field organization and evolution. Patterns of the Sun-as-star magnetic field during solar cycle 19 were obtained. The proposed technique can be useful for studying the solar magnetic field structure and evolution during times with no direct observations.

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Sun-like Stars: magnetic fields, cycles and exoplanets

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316003288 ◽

2015 ◽

Vol 11 (A29A) ◽

pp. 360-364

Author(s):

Rim Fares

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Large Scale ◽

Observational Constraints ◽

The Sun ◽

Field Generation ◽

Large Scale Magnetic Field ◽

Planetary Orbits ◽

Activity Cycles ◽

Magnetic Cycles

AbstractIn Sun-like stars, magnetic fields are generated in the outer convective layers. They shape the stellar environment, from the photosphere to planetary orbits. Studying the large-scale magnetic field of those stars enlightens our understanding of the field properties and gives us observational constraints for field generation dynamo models. It also sheds light on how “normal” the Sun is among Sun-like stars. In this contribution, I will review the field properties of Sun-like stars, focusing on solar twins and planet hosting stars. I will discuss the observed large-scale magnetic cycles, compare them to stellar activity cycles, and link that to what we know about the Sun. I will also discuss the effect of large-scale stellar fields on exoplanets, exoplanetary emissions (e.g. radio), and habitability.

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Variations of the Coronal Radiation in X-ray Related to Coronal Holes, Active Region Loop Systems, Bright Points

International Astronomical Union Colloquium ◽

10.1017/s0252921100024660 ◽

1994 ◽

Vol 143 ◽

pp. 159-171

Author(s):

Ester Antonucci

Keyword(s):

Magnetic Field ◽

Spatial Distribution ◽

Large Scale ◽

Coronal Holes ◽

Active Regions ◽

Coronal Magnetic Field ◽

Small Scale ◽

X Ray ◽

Coronal Structures

The coronal features observed in X-ray emission, varying from the small-scale, short-lived bright points to the large-scale, long-lived coronal holes, are closely associated with the coronal magnetic field and its topology, and their variability depends strongly on the solar cycle. Here we discuss the spatial distribution of the coronal structures, the frequency distribution of the brightness variations in active regions, and the role of magnetic reconnection in determining the variability of the coronal features, on the basis of the new observations of the soft X-ray emission recently obtained with the Yohkoh satellite and the NIXT experiment.

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The Toroidal Magnetic Field inside the Sun

International Astronomical Union Colloquium ◽

10.1017/s0252921100079616 ◽

1991 ◽

Vol 130 ◽

pp. 187-189

Author(s):

V.N. Krivodubskij ◽

A.E. Dudorov ◽

A.A. Ruzmaikin ◽

T.V. Ruzmaikina

Keyword(s):

Magnetic Field ◽

Large Scale ◽

Convection Zone ◽

The Sun ◽

Poloidal Magnetic Field ◽

Radial Gradient ◽

The Core ◽

Large Scale Magnetic Field ◽

Magnetic Buoyancy ◽

The Magnetic Field

Analysis of the fine structure of the solar oscillations has enabled us to determine the internal rotation of the Sun and to estimate the magnitude of the large-scale magnetic field inside the Sun. According to the data of Duvall et al. (1984), the core of the Sun rotates about twice as fast as the solar surface. Recently Dziembowski et al. (1989) have showed that there is a sharp radial gradient in the Sun’s rotation at the base of the convection zone, near the boundary with the radiative interior. It seems to us that the sharp radial gradients of the angular velocity near the core of the Sun and at the base of the convection zone, acting on the relict poloidal magnetic field Br, must excite an intense toroidal field Bф, that can compensate for the loss of the magnetic field due to magnetic buoyancy.

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The exceptional aspects of the confined X-class flares of solar active region 2192

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316000399 ◽

2015 ◽

Vol 11 (S320) ◽

pp. 60-63

Author(s):

Julia K. Thalmann ◽

Yang Su ◽

Manuela Temmer ◽

Astrid M. Veronig

Keyword(s):

Magnetic Field ◽

Active Region ◽

Large Scale ◽

Coronal Magnetic Field ◽

Active Region Noaa ◽

High Energies ◽

The Past ◽

Large Scale Magnetic Field ◽

High Level ◽

Mass Ejection

AbstractDuring late October 2014, active region NOAA 2192 caused an unusual high level of solar activity, within an otherwise weak solar cycle. While crossing the solar disk, during a period of 11 days, it was the source of 114 flares of GOES class C1.0 and larger, including 29 M- and 6 X-flares. Surprisingly, none of the major flares (GOES class M5.0 and larger) was accompanied by a coronal mass ejection, contrary to statistical tendencies found in the past. From modeling the coronal magnetic field of NOAA 2192 and its surrounding, we suspect that the cause of the confined character of the flares is the strong surrounding and overlying large-scale magnetic field. Furthermore, we find evidence for multiple magnetic reconnection processes within a single flare, during which electrons were accelerated to unusual high energies.

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OBLIQUE MAGNETIC FIELDS AND THE ROLE OF FRAME DRAGGING NEAR ROTATING BLACK HOLE

Acta Polytechnica ◽

10.14311/ap.2014.54.0398 ◽

2014 ◽

Vol 54 (6) ◽

pp. 398-413 ◽

Cited By ~ 8

Author(s):

Vladimír Karas ◽

Ondřej Kopáček ◽

Devaky Kunneriath

Keyword(s):

Magnetic Field ◽

Black Hole ◽

Large Scale ◽

Frame Dragging ◽

Rotating Black Hole ◽

Large Scale Magnetic Field ◽

Set Up ◽

Magnetic Null ◽

Future Work

<p>Magnetic null points can <span style="font-size: 10px;">develop near the ergosphere boundary of a rotating black hole by the combined effects of strong gravitational field and the frame-dragging mechanism. The induced electric component does not vanish in the magnetic null and an efficient process of particle acceleration can occur in its immediate vicinity. Furthermore, the effect of imposed (weak) magnetic field can trigger an onset of chaos in the motion of electrically charged particles. The model set-up appears to be relevant for low-accretion-rate nuclei of some galaxies which exhibit episodic accretion events (such as the Milky Way's supermassive black hole) embedded in a large-scale magnetic field of external origin with respect to the central black hole. In this contribution we summarise recent results and we give an outlook for future work with the focus on the role of gravito-magnetic effects caused by rotation of the black hole.</span></p>

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Active regions and the interplanetary magnetic field

Symposium - International Astronomical Union ◽

10.1017/s007418090002180x ◽

1968 ◽

Vol 35 ◽

pp. 390-394

Author(s):

John M. Wilcox ◽

Norman F. Ness ◽

Kenneth H. Schatten

Keyword(s):

Magnetic Field ◽

Interplanetary Magnetic Field ◽

Large Scale ◽

Early Stage ◽

Active Regions ◽

The Sun ◽

Sector Structure ◽

Archimedean Spiral ◽

Spiral Angle ◽

Scale Evolution

The relation of solar active regions to the large-scale sector structure of the interplanetary field is discussed. In the winter of 1963–64 (observed by the satellite IMP-1) the plage density was greatest in the leading portion of the sectors and lesser in the trailing portion of the sectors. The boundaries of the sectors (places at which the direction of the interplanetary magnetic field changed from toward the Sun to away from the Sun, or vice versa) were remarkably free of plages. The very fact that since the first observations in 1962 the average interplanetary field has almost always had the property of being either toward the Sun or away from the Sun (along the Archimedean spiral angle) continuously for several days must be considered in the discussion of large-scale evolution of active regions. Using the observed interplanetary magnetic field at 1 AU and a set of reasonable assumptions the magnetic configuration in the ecliptic from 0·4 AU to 1·2 AU has been reconstructed. In at least one case a pattern emerges which appears to be related to the evolution of an active region from an early stage in which the magnetic lines closely couple the preceding and following halves of the region to a later stage in which the two halves of the region are more widely separated.

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