scholarly journals The magnetic helicity density patterns from non-axisymmetric solar dynamo

2021 ◽  
Vol 87 (1) ◽  
Author(s):  
Valery V. Pipin
Keyword(s):  
Magnetic Field ◽  
Differential Rotation ◽  
Conservation Law ◽  
Large Scale ◽  
Solar Dynamo ◽  
Magnetic Helicity ◽  
Dynamo Model ◽  
Density Distributions ◽  
Large Scale Magnetic Field ◽  
Helicity Conservation

We study the helicity density patterns which can result from the emerging bipolar regions. Using the relevant dynamo model and the magnetic helicity conservation law we find that the helicity density patterns around the bipolar regions depend on the configuration of the ambient large-scale magnetic field, and in general they show a quadrupole distribution. The position of this pattern relative to the equator can depend on the tilt of the bipolar region. We compute the time–latitude diagrams of the helicity density evolution. The longitudinally averaged effect of the bipolar regions shows two bands of sign for the density distributions in each hemisphere. Similar helicity density patterns are provided by the helicity density flux from the emerging bipolar regions subjected to surface differential rotation.

scholarly journals Helicity–vorticity turbulent pumping of magnetic fields in the solar dynamo

2012 ◽  
Vol 8 (S294) ◽  
pp. 367-368
Author(s):  
V. V. Pipin
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Differential Rotation ◽  
Large Scale ◽  
Convection Zone ◽  
Solar Dynamo ◽  
Solar Convection Zone ◽  
Solar Convection ◽  
Large Scale Magnetic Field ◽  
Convective Motions

AbstractThe interaction of helical convective motions and differential rotation in the solar convection zone results in turbulent drift of a large-scale magnetic field. We discuss the pumping mechanism and its impact on the solar dynamo.

scholarly journals The origin and effect of hemispheric helicity imbalance in solar dynamo

2020 ◽  
Vol 86 (3) ◽  
Author(s):  
Shangbin Yang ◽  
V. V. Pipin ◽  
D. D. Sokoloff ◽  
K. M. Kuzanyan ◽  
Hongqi Zhang
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Time Lag ◽  
Magnetic Helicity ◽  
Dynamo Model ◽  
Small Scale ◽  
Large Scale Magnetic Field ◽  
The Difference ◽  
Random Fluctuations ◽  
Parity Breaking

In this paper we study the effects of the net magnetic helicity density on the hemispheric symmetry of the dynamo generated large-scale magnetic field. Our study employs the axisymmetric dynamo model which takes into account the nonlinear effect of magnetic helicity conservation. We find that, on the surface, the net magnetic helicity follows the evolution of the parity of the large-scale magnetic field. Random fluctuations of the $\unicode[STIX]{x1D6FC}$ -effect and the helicity fluxes can invert the causal relationship, i.e. the net magnetic helicity or the imbalance of magnetic helicity fluxes can drive the magnetic parity breaking. We also found that evolution of the net magnetic helicity of the small-scale fields follows the evolution of the net magnetic helicity of the large-scale fields with some time lag. We interpret this as an effect of the difference of the magnetic helicity fluxes out of the Sun from the large and small scales.

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.

scholarly journals A way to detect the magnetic helicity using the observable polarized radio emission

2010 ◽  
Vol 6 (S274) ◽  
pp. 185-191
Author(s):  
Rodion Stepanov ◽  
Antonina Volegova
Keyword(s):  
Magnetic Field ◽  
Radio Emission ◽  
Large Scale ◽  
Magnetic Helicity ◽  
Polarization Degree ◽  
Main Role ◽  
Frequency Range ◽  
Principal Solution ◽  
Large Scale Magnetic Field ◽  
Rotation Measure

AbstractWe discuss inverse problem of detection turbulence magnetic field helical properties using radio survey observations statistics. In this paper, we present principal solution which connects magnetic helicity and correlation between Faraday rotation measure and polarization degree of radio synchrotron emission. The effect of depolarization plays the main role in this problem and allows to detect magnetic helicity for certain frequency range of observable radio emission. We show that the proposed method is mainly sensitive to a large-scale magnetic field component.

scholarly journals Current helicity constraints in solar dynamo models

2012 ◽  
Vol 8 (S294) ◽  
pp. 313-318
Author(s):  
D. Sokoloff ◽  
H. Zhang ◽  
D. Moss ◽  
N. Kleeorin ◽  
K. Kuzanyan ◽  
...  
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Mean Field ◽  
Active Regions ◽  
Solar Dynamo ◽  
Magnetic Helicity ◽  
Dynamo Model ◽  
Small Scale ◽  
Mean Field Dynamo ◽  
Current Helicity

AbstractWe investigate to what extent the current helicity distribution observed in solar active regions is compatible with solar dynamo models. We use an advanced 2D mean-field dynamo model with dynamo action largely concentrated near the bottom of the convective zone, and dynamo saturation based on the evolution of the magnetic helicity and algebraic quenching. For comparison, we also studied a more basic 2D mean-field dynamo model with simple algebraic alpha quenching only. Using these numerical models we obtain butterfly diagrams for both the small-scale current helicity and the large-scale magnetic helicity, and compare them with the butterfly diagram for the current helicity in active regions obtained from observations. This comparison shows that the current helicity of active regions, as estimated by −A·B evaluated at the depth from which the active region arises, resembles the observational data much better than the small-scale current helicity calculated directly from the helicity evolution equation. Here B and A are respectively the dynamo generated mean magnetic field and its vector potential.

scholarly journals Spin-Down of Solar-Type Stars with Internal Magnetic Fields

1993 ◽  
Vol 137 ◽  
pp. 464-468
Author(s):  
Paul Charbonneau ◽  
Keith B. Macgregor
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Differential Rotation ◽  
Large Scale ◽  
Back Reaction ◽  
Large Set ◽  
Large Scale Magnetic Field ◽  
Solar Type ◽  
Solar Type Star ◽  
Selection Of

AbstractWe present a selection of results from a large set of numerical simulations of the spin-down of a solar-type star containing a large scale magnetic field in its radiative interior. Our computations are dynamical, in that they take into account both the generation of the toroidal component by the wind-induced shear endits back-reaction on the azimuthal flow. Our results demonstrate the existence of classes of internal magnetic fields that can accomodate rapid spin-down near the ZAMS, and yield weak internal differential rotation by the solar age.

scholarly journals Magnetic Helicity Generated together with Evolution of the Large-Scale Magnetic Field

2005 ◽  
Vol 13 ◽  
pp. 134-134
Author(s):  
Pavel Ambrož
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Magnetic Helicity ◽  
Large Scale Magnetic Field

AbstractText below is an extended abstract of the poster, presented on JD03 session during 25th GA IAU in Sydney.

scholarly journals Key Problems of Flat Objects Dynamo Theory and Ways of Their Solution

1990 ◽  
Vol 140 ◽  
pp. 97-106
Author(s):  
F. Krause ◽  
R. Meinel ◽  
D. Elstner ◽  
G. Rüdiger
Keyword(s):  
Magnetic Field ◽  
Differential Rotation ◽  
Present Status ◽  
Large Scale ◽  
Dynamo Theory ◽  
Large Scale Magnetic Field ◽  
Galaxy Model

The present status of galactic dynamo theory is discussed. A new concept which allows the determination of marginal dynamo numbers for axisymmetric as well as non-axisymmetric large-scale magnetic field modes in axisymmetric disks is applied to a simple galaxy model. The results obtained so far show that a preference of non-axisymmetric fields can only be expected if the α-effect is highly anisotropic and the differential rotation is not too strong. Mostly axisymmetric-spiral fields have to be expected.

Generalized magnetic helicity, large-scale magnetic field, and dynamo saturation

2003 ◽  
Vol 10 (6) ◽  
pp. 2287-2295 ◽  
Author(s):  
L. J. Milano ◽  
W. H. Matthaeus ◽  
P. Dmitruk
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Magnetic Helicity ◽  
Large Scale Magnetic Field
Sign in / Sign up

Export Citation Format

Share Document