scholarly journals Solar Field Mapping and Dynamo Behavior

2012 ◽  
Vol 2012 ◽  
pp. 1-28 ◽  
Author(s):  
Kenneth H. Schatten
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Large Scale ◽  
Coronal Holes ◽  
The Sun ◽  
Cellular Automata Model ◽  
Large Scale Magnetic Field ◽  
Planetary Environment ◽  
Algorithmic Model ◽  
Solar Field

We discuss the importance of the Sun’s large-scale magnetic field to the Sun-Planetary environment. This paper narrows its focus down to the motion and evolution of the photospheric large-scale magnetic field which affects many environments throughout this region. For this purpose we utilize a newly developed Netlogo cellular automata model. The domain of this algorithmic model is the Sun’s photosphere. Within this computational space are placed two types of entities or agents; one may refer to them as bluebirds and cardinals; the former carries outward magnetic flux and the latter carries out inward magnetic flux. One may simply call them blue and red agents. The agents provide a granularity with discrete changes not present in smooth MHD models; they undergo three processes: birth, motion, and death within the photospheric domain. We discuss these processes, as well as how we are able to develop a model that restricts its domain to the photosphere and allows the deeper layers to be considered only through boundary conditions. We show the model’s ability to mimic a number of photospheric magnetic phenomena: the solar cycle (11-year) oscillations, the Waldmeier effect, unipolar magnetic regions (e.g. sectors and coronal holes), Maunder minima, and the march/rush to the poles involving the geometry of magnetic field reversals. We also discuss why the Sun sometimes appears as a magnetic monopole, which of course requires no alteration of Maxwell’s equations.

scholarly journals Numerical Simulations of Large-scale Solar Magnetic Fields

1985 ◽  
Vol 38 (6) ◽  
pp. 999 ◽  
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.

Coronal Holes and the Locations of the LDE-Type Flares

1994 ◽  
Vol 144 ◽  
pp. 263-266
Author(s):  
A. Antalová
Keyword(s):  
Magnetic Field ◽  
Qualitative Analysis ◽  
Large Scale ◽  
Coronal Holes ◽  
Polarity Reversal ◽  
Flare Activity ◽  
The Sun ◽  
Magnetic Reversal ◽  
Physical Processes ◽  
Large Scale Magnetic Field

AbstractA qualitative analysis is presented of a possible link between two physical processes on the Sun, namely the gradual magnetic reversal of the large-scale magnetic field of the Sun, and the increase of a flare activity in the solar sectors where the polarity reversal of the faint large-scale magnetic field is observed. The data in Table 1 (years 1976-1979) show that the LDE flare producting nests of the 21st cycle were located within and along the borders of reversed sectors. The flaring centers precede the formation of coronal holes.

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

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.

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

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.

scholarly journals Sun-like Stars: magnetic fields, cycles and exoplanets

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.

scholarly journals The Toroidal Magnetic Field inside the Sun

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.

Solar Dynamo

2020 ◽  
Author(s):  
Robert Cameron
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Differential Rotation ◽  
Large Scale ◽  
Toroidal Field ◽  
Solar Dynamo ◽  
Small Scale ◽  
The Sun ◽  
The Magnetic Field

The solar dynamo is the action of flows inside the Sun to maintain its magnetic field against Ohmic decay. On small scales the magnetic field is seen at the solar surface as a ubiquitous “salt-and-pepper” disorganized field that may be generated directly by the turbulent convection. On large scales, the magnetic field is remarkably organized, with an 11-year activity cycle. During each cycle the field emerging in each hemisphere has a specific East–West alignment (known as Hale’s law) that alternates from cycle to cycle, and a statistical tendency for a North-South alignment (Joy’s law). The polar fields reverse sign during the period of maximum activity of each cycle. The relevant flows for the large-scale dynamo are those of convection, the bulk rotation of the Sun, and motions driven by magnetic fields, as well as flows produced by the interaction of these. Particularly important are the Sun’s large-scale differential rotation (for example, the equator rotates faster than the poles), and small-scale helical motions resulting from the Coriolis force acting on convective motions or on the motions associated with buoyantly rising magnetic flux. These two types of motions result in a magnetic cycle. In one phase of the cycle, differential rotation winds up a poloidal magnetic field to produce a toroidal field. Subsequently, helical motions are thought to bend the toroidal field to create new poloidal magnetic flux that reverses and replaces the poloidal field that was present at the start of the cycle. It is now clear that both small- and large-scale dynamo action are in principle possible, and the challenge is to understand which combination of flows and driving mechanisms are responsible for the time-dependent magnetic fields seen on the Sun.

The large-scale magnetic field on the Sun: The equatorial region

2000 ◽  
Vol 44 (2) ◽  
pp. 103-111 ◽  
Author(s):  
V. N. Obridko ◽  
B. D. Shel'ting
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Equatorial Region ◽  
The Sun ◽  
Large Scale Magnetic Field

scholarly journals Two classes of eruptive events during Solar Minimum

2021 ◽  
Author(s):  
Prantika Bhowmik ◽  
Anthony Yeates
Keyword(s):  
Magnetic Field ◽  
Free Energy ◽  
Magnetic Flux ◽  
Solar Minimum ◽  
Large Scale ◽  
Solar Surface ◽  
Coronal Holes ◽  
Active Regions ◽  
Coronal Magnetic Field ◽  
The Magnetic Field

<p>During Solar Minimum, the Sun is perceived to be quite inactive with barely any spots emerging on the solar surface. Consequently, we observe a drop in the number of highly energetic events such as solar flares and coronal mass ejections (CMEs), which are often associated with active regions on the photosphere. However, our magnetofrictional simulations during the minimum period suggest that the solar corona could still be significantly dynamic while evolving in response to the large-scale shearing velocities on the solar surface. The non-potential evolution of the corona leads to the accumulation of magnetic free energy and helicity, which is periodically lost through eruptive events. Our study shows that these events can be categorised into two distinct classes. One set of events are caused due to full-scale eruption of low-lying coronal flux ropes and could be associated with occasional filament erupting CMEs observed during Solar Minimum. The other set of events are not driven by destabilisation of low-lying structures but rather by eruption from overlying sheared arcades. These could be linked with streamer blowouts or stealth CMEs. The two classes differ considerably in the amount of magnetic flux and helicity shed through the outer coronal boundary. We additionally investigate how other measurables such as current, open magnetic flux, free energy, coronal holes area, and the horizontal component of the magnetic field on the outer model boundary vary during the two classes of event. This study demonstrates and emphasises the importance and necessity of understanding the dynamics of the coronal magnetic field during Solar Minimum.</p>

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