scholarly journals Convective dynamo action in a spherical shell: symmetries and modulation

2016 ◽  
Vol 799 ◽  
Author(s):  
Raphaël Raynaud ◽  
Steven M. Tobias
Keyword(s):  
Solar Activity ◽  
Magnetic Fields ◽  
Spherical Shell ◽  
Differential Rotation ◽  
Three Dimensional ◽  
Important Process ◽  
Dynamo Action ◽  
Grand Minima

We consider dynamo action driven by three-dimensional rotating anelastic convection in a spherical shell. Motivated by the behaviour of the solar dynamo, we examine the interaction of hydromagnetic modes with different symmetries and demonstrate how complicated interactions between convection, differential rotation and magnetic fields may lead to modulation of the basic cycle. For some parameters, type 1 modulation occurs by the transfer of energy between modes of different symmetries with little change in the overall amplitude; for other parameters, the modulation is of type 2, where the amplitude is significantly affected (leading to grand minima in activity) without significant changes in symmetry. Most importantly, we identify the presence of ‘supermodulation’ in the solutions, where the activity switches chaotically between type 1 and type 2 modulation; this is believed to be an important process in solar activity.

Three-dimensional kinematics of the lunate, hamate, capitate and triquetrum with type 1 or 2 lunate morphology

2017 ◽  
Vol 43 (4) ◽  
pp. 380-386 ◽  
Author(s):  
Shingo Abe ◽  
Hisao Moritomo ◽  
Kunihiro Oka ◽  
Kazuomi Sugamoto ◽  
Kenji Kasubuchi ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Wrist Joint ◽  
Three Dimensional ◽  
Wrist Flexion ◽  
Ulnar Deviation ◽  
Dart Throwing ◽  
Carpal Kinematics ◽  
Throwing Motion

The purpose of this study was to investigate the differences in three-dimensional carpal kinematics between type 1 and 2 lunates. We studied 15 instances of wrist flexion to extension (nine type 1, six type 2), 13 of radial to ulnar deviation (seven type 1, six type 2), and 12 of dart-throwing motion (six each of type 1 and 2) in 25 normal participants based on imaging with computerized tomography. Mean proximal translation of the distal articular midpoint of the triquetrum relative to type 2 lunates during wrist radioulnar deviation was 2.9 mm (standard deviation (SD) 0.7), which was significantly greater than for type 1 lunates, 1.6 mm (SD 0.6). The hamate contacted the lunate in ulnar deviation and ulnar flexion of wrists with type 2 lunates but not with type 1. We conclude that the four-corner kinematics of the wrist joint are different between type 1 and 2 lunates.

Numerical Short-Term Solar Activity Forecasting

2017 ◽  
Vol 13 (S335) ◽  
pp. 243-249 ◽  
Author(s):  
Huaning Wang ◽  
Yihua Yan ◽  
Han He ◽  
Xin Huang ◽  
Xinghua Dai ◽  
...  
Keyword(s):  
Solar Activity ◽  
Magnetic Fields ◽  
Solar Atmosphere ◽  
Magnetic Energy ◽  
Three Dimensional ◽  
Active Regions ◽  
Short Term ◽  
Solar Active Regions ◽  
Solar Eruptions ◽  
Dimensional Reconstruction

AbstractIt is well known that the energy for solar eruptions comes from magnetic fields in solar active regions. Magnetic energy storage and dissipation are regarded as important physical processes in the solar corona. With incomplete theoretical modeling for eruptions in the solar atmosphere, activity forecasting is mainly supported with statistical models. Solar observations with high temporal and spatial resolution continuously from space well describe the evolution of activities in the solar atmosphere, and combined with three dimensional reconstruction of solar magnetic fields, makes numerical short-term (within hours to days) solar activity forecasting possible. In the current report, we propose the erupting frequency and main attack direction of solar eruptions as new forecasts and present the prospects for numerical short-term solar activity forecasting based on the magnetic topological framework in solar active regions.

scholarly journals Simulations of Core Convection Dynamos in Rotating A-type Stars

2004 ◽  
Vol 215 ◽  
pp. 376-377
Author(s):  
Matthew Browning ◽  
Allan Sacha Brun ◽  
Juri Toomre
Keyword(s):  
Magnetic Field ◽  
Numerical Simulations ◽  
Differential Rotation ◽  
Three Dimensional ◽  
Dynamo Action ◽  
The Core ◽  
Core Convection ◽  
Seed Field ◽  
Initial Seed ◽  
Three Dimensional Simulations

We have conducted preliminary numerical simulations of a core convection dynamo operating within an A-type star of two solar masses. Convection within the core clearly can admit magnetic dynamo action. Magnetic field strengths in our three-dimensional simulations grow by many orders of magnitude, from an initial seed field to kilo-Gauss levels. We discuss the differential rotation and magnetic field sustained in our simulations.

scholarly journals Three-dimensional structure of a mouse-adapted type 2/type 1 poliovirus chimera.

1991 ◽  
Vol 10 (9) ◽  
pp. 2331-2341 ◽  
Author(s):  
T.O. Yeates ◽  
D.H. Jacobson ◽  
A. Martin ◽  
C. Wychowski ◽  
M. Girard ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Dimensional Structure ◽  
Three Dimensional Structure

Challenges of magnetism in the turbulent Sun

2006 ◽  
Vol 2 (S239) ◽  
pp. 488-493
Author(s):  
Allan Sacha Brun ◽  
Mark S. Miesch ◽  
Juri Toomre
Keyword(s):  
Magnetic Fields ◽  
Differential Rotation ◽  
Convection Zone ◽  
Three Dimensional ◽  
Reynolds Stresses ◽  
Turbulent Layer ◽  
Solar Convection ◽  
Mean Fields ◽  
Global Modelling ◽  
Parallel Supercomputers

AbstractThree-dimensional global modelling of turbulent convection coupled to rotation and magnetism within the Sun are revealing processes relevant to many stars. We study spherical shells of compressible convection spanning many density scale heights using the MHD version of the anelastic spherical harmonic (ASH) code on massively parallel supercomputers. The simulations reveal that strong magnetic fields can be realized in the bulk of the solar convection zone while still attaining differential rotation profiles that make good contact with helioseismic findings. We find that the Maxwell and Reynolds stresses present in such a turbulent layer play an important role in redistributing angular momentum, with the latter maintaining the differential rotation, aided by baroclinic forcing at the base of the convection zone which is consistent with a tachocline there. The dynamo processes generate strong non-axisymmetric and intermittent fields and weak mean (axisymmetric) fields, but do not possess a regular cyclic magnetism. The explicit inclusion of penetrative convection into the tachocline below is modifying such behavior, serving to build strong toroidal magnetic fields there that may yield more prominent mean fields that have the potential of erupting upward.

On the rigidity of triangulated hyperbolic paraboloids

1988 ◽  
Vol 418 (1855) ◽  
pp. 425-452 ◽  
Keyword(s):  
Three Dimensional ◽  
Load Test ◽  
Equilibrium Equations ◽  
Triangulated Surfaces ◽  
Historic Review ◽  
Equilibrium Matrix ◽  
Geometric Arrangements ◽  
Hyperbolic Paraboloids

The paper investigates the rigidity of two classes of three-dimensional pin-jointed assemblies which describe triangulated surfaces of hyperbolic paraboloidal shape: type 1 with straight boundaries, and type 2 with parabolic boundaries. The two arrangements have identical horizontal plans. The investigation begins with a brief historic review of techniques for detecting lack of rigidity. The behaviour of both type-1 and type-2 assemblies depends on the number n of bars on each edge of the structure and, although both geometric arrangements satisfy Maxwell rule (3 j ═ b , where j is the number of joints and b is the number of bars) for any value of n , all type-1 assemblies with n even and greater than 2 and type-2 assemblies with n > 1 are in fact not rigid. This result is first proved for some specific cases by the zero-load test; and then for arbitrary values of n . The equilibrium equations of each joint are written down in terms of a stress function, and are then assembled in an equilibrium matrix whose rank is found by general matrix manipulations. The number of inextensional mechanisms and static redundancies is also obtained. The rigidity of assemblies consisting of four interconnected type-1 hyperbolic paraboloidal sheets is also discussed, and it is concluded that they are equally prone to the same kind of misbehaviour.

scholarly journals Magnetohydrodynamic Simulation of the Evolution of Bipolar Magnetic Regions

1993 ◽  
Vol 141 ◽  
pp. 98-107 ◽  
Author(s):  
S. T. Wu ◽  
C. L. Yin ◽  
P. Mcintosh ◽  
E. Hildner
Keyword(s):  
Magnetic Fields ◽  
Magnetic Flux ◽  
Differential Rotation ◽  
Solar Surface ◽  
Effective Diffusion ◽  
Three Dimensional ◽  
Meridional Flow ◽  
Flux Transport ◽  
Turbulence Effects ◽  
Convective Motions

AbstractIt has been recognized that the magnetic flux observed on the solar surface appears first in low latitudes, and then this flux is gradually dispersed by super granular convective motions and meridional circulation. Theoretically, the magnetic flux transport could be explained by the interactions between magnetic fields and plasma flows on the solar surface through the theory of magnetohydrodynamics.To understand this physical scenario, a quasi-three-dimensional, time-dependent, MHD model with differential rotation, meridional flow and effective diffusion as well as cyclonic turbulence effects is developed. Numerical experiments are presented for the study of Bipolar Magnetic Regions (BMRs). When the MHD effects are ignored, our model produced the classical results (Leighton, Astrophys. J., 146, 1547, 1964). The full model’s numerical results demonstrate that the interaction between magnetic fields and plasma flow (i.e., MHD effects), observed together with differential rotation and meridional flow, gives rise to the observed complexity of the evolution of BMRs.

scholarly journals Dynamo coefficients from the Tayler instability

2010 ◽  
Vol 6 (S271) ◽  
pp. 213-217 ◽  
Author(s):  
Rainer Arlt ◽  
Günther Rüdiger
Keyword(s):  
Spherical Shell ◽  
Northern Hemisphere ◽  
Differential Rotation ◽  
Initial Value ◽  
Dynamo Action ◽  
Fundamental Interest ◽  
Stellar Radiation ◽  
Current Helicity

AbstractCurrent-driven instabilities in stellar radiation zones, to which we refer as Tayler instabilities, can lead to complex nonlinear evolutions. It is of fundamental interest whether magnetically driven turbulence can lead to dynamo action in these radiative zones. We investigate initial-value simulations in a 3D spherical shell including differential rotation. The Tayler instability is connected with a very weak kinetic helicity, stronger current helicity, and a positive αφφ in the northern hemisphere. The amplitudes are small compared to the effect of the tangential cylinder producing an eddy with negative kinetic helicity and negative αφφ in the northern hemisphere. The αφφ from the Tayler instability reaches about 1% of the rms velocity.

scholarly journals Targeting Alcohol Septal Ablation in Patients with Obstructive Hypertrophic Cardiomyopathy Candidates for Surgical Myectomy: Added Value of Three-Dimensional Intracoronary Myocardial Contrast Echocardiography

2021 ◽  
Vol 10 (10) ◽  
pp. 2166
Author(s):  
Giovanni La La Canna ◽  
Iside Scarfò ◽  
Irina Arendar ◽  
Antonio Colombo ◽  
Lucia Torracca ◽  
...  
Keyword(s):  
High Risk ◽  
Three Dimensional ◽  
Added Value ◽  
Alcohol Septal Ablation ◽  
High Risk Type ◽  
Life Threatening ◽  
Surgical Myectomy

Background: Myocardial contrast two-dimensional echocardiography (MC-2DE) is widely used to address alcohol septal ablation (ASA) in obstructive hypertrophic cardiomyopathy (HCM). Owing to its limited cut-planes, MC-2DE may inaccurately identify the contrast misplacement associated with an unsuccessful or complicated ASA outcome. Objective: The aim of this study was to assess the added value of myocardial contrast three-dimensional echocardiography (MC-3DE) compared with MC-2DE to identify the appropriate matching between the target septal zone (TSZ) and coronary artery branch for safe and long-term effective ASA in HCM patients. Methods: A consecutive series of 52 symptomatic obstructive HCM patients referred for isolated surgical myectomy (SM) was analyzed with MC-2DE and MC-3DE following injection of echocontrast into one or more septal branches. MC-2DE and MC-3DE patterns were categorized according to complete (Type 1) or incomplete (Type 2) TSZ covering, high-risk (Type 3) exceeding TSZ, or life-threatening outside TSZ distribution (Type 4). Results: MC-2DE per patient analysis showed a Type 1 pattern in 32 patients and Types 2–4 in the remaining 20 patients; subsequent MC-3DE analysis provided a re-phenotyping of MC-2DE findings in 22 of the 52 patients (42%), showing a high-risk Type 2 pattern in 17 of the 32 patients with Type 1, and a new life-threatening Type 4 in three patients with Type 2, respectively. All patients with MC-3DE Type 1 pattern underwent safe and effective ASA with a long-term uneventful follow-up, while the remaining patients underwent SM. Conclusions: Refining high risk or life-threatening contrast misplacement, MC-3DE is more accurate than conventional MC-2DE to target safe and long-term effective septal reduction with ASA in obstructive HCM patients referred for isolated SM.

scholarly journals Magnetic Field Generation by Galactic Winds

1993 ◽  
Vol 157 ◽  
pp. 357-365 ◽  
Author(s):  
S.J. Spencer ◽  
L.E. Cram
Keyword(s):  
Magnetic Fields ◽  
Large Scale ◽  
Three Dimensional ◽  
Thin Disk ◽  
Magnetic Field Generation ◽  
Dynamo Action ◽  
Disk Model ◽  
Disk Plane ◽  
Large Scale Flow ◽  
The One

A new mechanism is presented for the local amplification and possible global dynamo maintenance of non-axisymmetric large-scale magnetic fields in disk galaxies. Shear in a galactic wind or large-scale flow of ionised gas with components axial and radial to the disk plane may regenerate large-scale magnetic fields.Numerical results are presented from kinematic mathematical models based on a local (thin disk) approximation and an exact three-dimensional formulation. The one-dimensional thin-disk model illustrates the possibility of exponential amplification and the resulting local axial spatial structure of large-scale galactic magnetic fields. Three-dimensional results support the possibility of global wind dynamo action.

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