scholarly journals Helioseismic inferences on subsurface solar convection

2006 ◽  
Vol 2 (S239) ◽  
pp. 113-121
Author(s):  
Alexander G. Kosovichev
Keyword(s):  
Large Scale ◽  
Meridional Flow ◽  
Polar Regions ◽  
Flux Transport ◽  
Solar Convection Zone ◽  
Solar Convection ◽  
New Methods ◽  
Global Properties ◽  
The Mean ◽  
Depth Stratification

AbstractHelioseismology has provided robust estimates of global properties of the solar convection zone, its depth, stratification, and revealed rotational shear layers at the boundaries. New methods of local helioseismology provide 3D maps of subsurface convective flows. In the quiet Sun regions, these maps reveal that supergranular-scale convection extends to the depth of 12–15 Mm. Analysis of evolution of the supergranular convection pattern shows evidence for a wave-like behavior which might be related to the interaction between convection and the subsurface rotational sheer layer. Helioseismology also reveals large-scale circulation flows around magnetic regions. These flows affect the evolution of the mean meridional flow during the solar cycle and, probably, the magnetic flux transport from mid-latitudes to the polar regions, a process important for solar dynamo theories. Helioseismic measurements on a smaller scale, below sunspots, give insight on how convection interacts with strong magnetic fields.

scholarly journals Subsurface Flows with Advancing Solar Cycle Using Dense-Pack Ring-Diagram Analyses

2001 ◽  
Vol 203 ◽  
pp. 211-214
Author(s):  
D. A. Haber ◽  
B. W. Hindman ◽  
J. Toomre ◽  
R. S. Bogart ◽  
F. Hill
Keyword(s):  
Solar Cycle ◽  
Large Scale ◽  
Doppler Velocity ◽  
Solar Convection Zone ◽  
Zonal Flows ◽  
Solar Convection ◽  
Doppler Imager ◽  
Ring Diagram ◽  
Subsurface Flows ◽  
The Mean

Ring-diagram analyses have become a powerful local helioseismic tool for studying large-scale flows in the upper solar convection zone. Using this technique on a dense-pack mosaic of many small regions extracted from the full-disk Doppler velocity data taken with the Michelson Doppler Imager (MDI) on SOHO, we study how the mean meridional and zonal flows vary with depth and latitude over the course of the advancing solar cycle from 1996 to 2000.

scholarly journals Helioseismic Observations of Solar Convection Zone Dynamics

2010 ◽  
Vol 6 (S271) ◽  
pp. 15-22
Author(s):  
Frank Hill ◽  
Rachel Howe ◽  
Rudi Komm ◽  
Irene González Hernández ◽  
Shukur Kholikov ◽  
...  
Keyword(s):  
Large Scale ◽  
Convection Zone ◽  
Global Analysis ◽  
Torsional Oscillation ◽  
Temporal Variations ◽  
Flare Activity ◽  
Flux Transport ◽  
Near Surface ◽  
Solar Convection Zone ◽  
Solar Convection

AbstractThe large-scale dynamics of the solar convection zone have been inferred using both global and local helioseismology applied to data from the Global Oscillation Network Group (GONG) and the Michelson Doppler Imager (MDI) on board SOHO. The global analysis has revealed temporal variations of the “torsional oscillation” zonal flow as a function of depth, which may be related to the properties of the solar cycle. The horizontal flow field as a function of heliographic position and depth can be derived from ring diagrams, and shows near-surface meridional flows that change over the activity cycle. Time-distance techniques can be used to infer the deep meridional flow, which is important for flux-transport dynamo models. Temporal variations of the vorticity can be used to investigate the production of flare activity. This paper summarizes the state of our knowledge in these areas.

scholarly journals Non-Linear Diamagnetic Transport of the Large-Scale Magnetic Field in the Solar Convection Zone

1993 ◽  
Vol 157 ◽  
pp. 49-50
Author(s):  
V.N. Krivodubskij
Keyword(s):  
Magnetic Field ◽  
Turbulence Intensity ◽  
Large Scale ◽  
Convection Zone ◽  
Back Reaction ◽  
Solar Convection Zone ◽  
Solar Convection ◽  
Large Scale Magnetic Field ◽  
Magnetic Buoyancy ◽  
The Mean

The mean magnetic field transport due to inhomogeneity of the turbulence intensity is considered taking the field back reaction on motion into account. In spite of the magnetic quenching, the downward diamagnetic pumping is still powerful enough to keep the fields of 3 to 4 kG strength near the SCZ base against the magnetic buoyancy.

scholarly journals Does the mean-field α effect have any impact on the memory of the solar cycle?

2020 ◽  
Vol 642 ◽  
pp. A51
Author(s):  
Soumitra Hazra ◽  
Allan Sacha Brun ◽  
Dibyendu Nandy
Keyword(s):  
Solar Cycle ◽  
Mean Field ◽  
Solar Dynamo ◽  
Dynamo Model ◽  
Solar Cycles ◽  
Poloidal Field ◽  
Flux Transport ◽  
Solar Convection ◽  
The Mean ◽  
And Diffusion

Context. Predictions of solar cycle 24 obtained from advection-dominated and diffusion-dominated kinematic dynamo models are different if the Babcock–Leighton mechanism is the only source of the poloidal field. Some previous studies argue that the discrepancy arises due to different memories of the solar dynamo for advection- and diffusion-dominated solar convection zones. Aims. We aim to investigate the differences in solar cycle memory obtained from advection-dominated and diffusion-dominated kinematic solar dynamo models. Specifically, we explore whether inclusion of Parker’s mean-field α effect, in addition to the Babcock–Leighton mechanism, has any impact on the memory of the solar cycle. Methods. We used a kinematic flux transport solar dynamo model where poloidal field generation takes place due to both the Babcock–Leighton mechanism and the mean-field α effect. We additionally considered stochastic fluctuations in this model and explored cycle-to-cycle correlations between the polar field at minima and toroidal field at cycle maxima. Results. Solar dynamo memory is always limited to only one cycle in diffusion-dominated dynamo regimes while in advection-dominated regimes the memory is distributed over a few solar cycles. However, the addition of a mean-field α effect reduces the memory of the solar dynamo to within one cycle in the advection-dominated dynamo regime when there are no fluctuations in the mean-field α effect. When fluctuations are introduced in the mean-field poloidal source a more complex scenario is evident, with very weak but significant correlations emerging across a few cycles. Conclusions. Our results imply that inclusion of a mean-field α effect in the framework of a flux transport Babcock–Leighton dynamo model leads to additional complexities that may impact memory and predictability of predictive dynamo models of the solar cycle.

scholarly journals On the Dynamics of the Solar Convection Zone

1980 ◽  
Vol 51 ◽  
pp. 15-16
Author(s):  
Bernard R. Durney ◽  
Hendrik C. Spruit
Keyword(s):  
Distribution Function ◽  
Energy Equation ◽  
Convection Zone ◽  
Turbulent Viscosity ◽  
Rotating Stars ◽  
Solar Convection Zone ◽  
Solar Convection ◽  
Convective Motions ◽  
The Mean ◽  
Convective Cells

AbstractWe derive expressions for the turbulent viscosity and turbulent conductivity applicable to convection zones of rotating stars. We assume that the dimensions of the convective cells are known and derive a simple distribution function for the turbulent convective velocities under the influence of rotation. From this distribution function (which includes, in particular, the stabilizing effect of rotation on convection) we calculate in the mixing-length approximation: i) the turbulent Reynolds stresstensor and ii) the expression for the heat flux in terms of the superadiabatic gradient. The contributions of the turbulent convective motions to the mean momentum and energy equation are treated consistently, and assumptions about the turbulent viscosity and heat transport are replaced by assumptions about the turbulent flow itself. The free parameters in our formalism are the relative cell sizes and their dependence on depth and latitude.

Large Scale Flows in the Solar Convection Zone

2008 ◽  
Vol 144 (1-4) ◽  
pp. 151-173 ◽  
Author(s):  
Allan Sacha Brun ◽  
Matthias Rempel
Keyword(s):  
Large Scale ◽  
Convection Zone ◽  
Solar Convection Zone ◽  
Solar Convection

Die Lithiumhäufigkeit und die Struktur der äußeren Konvektionszone in sonnenähnlichen Sternen

1966 ◽  
Vol 21 (7) ◽  
pp. 1107-1115
Author(s):  
K.-H. Böhm
Keyword(s):  
Isotope Ratio ◽  
Main Sequence ◽  
Convection Zone ◽  
Mixing Process ◽  
Lithium Abundance ◽  
Solar Convection Zone ◽  
Solar Convection ◽  
The Mean ◽  
Convective Overshoot ◽  
Slow Timescale

The observations of the Lithium abundance and the isotope ratio Li6/Li7 in stars are briefly reviewed and some simple conclusions are drawn. It is emphasized that — in addition to the mechanism proposed by BODENHEIMER — a slow (timescale ≈ 109 years) mixing process in main sequence F and G stars is necessary to account for the observations.The present state of the theory of convective overshooting is reviewed in this context. Two new models of the outer solar convection zone are presented. The temperature at their lower boundaries are 2.04 x 106 °K and 2.27 x 106 °K, showing that only a rather small convective overshoot may be sufficient for mixing the matter in the convection zone with the layers, in which Li7 is burnt.Our models differ from earlier ones, because (when calculating the mean stratification) we take into account the condition that the mixing length can nowhere be larger than the distance from the nearest boundary of the convection zone. It is shown that this approach also leads to a slight change of the numerical factors in the formulae usually used.

scholarly journals On the Detection of Subphotospheric Convective Velocities and Temperature Fluctuations

1983 ◽  
Vol 66 ◽  
pp. 401-410
Author(s):  
D. O. Gough ◽  
J. Toomre
Keyword(s):  
Large Scale ◽  
Temperature Fluctuations ◽  
Wave Number ◽  
Convective Velocity ◽  
Solar Convection Zone ◽  
Solar Convection ◽  
Wave Patterns ◽  
Large Scale Flow ◽  
Low Amplitude ◽  
High Degree

AbstractA procedure is outlined for estimating the influence of large-scale convective eddies on the wave patterns of five-minute oscillations of high degree. The method is applied to adiabatic oscillations, with frequency ω and wave number k, of a plane-parallel polytropic layer upon which is imposed a low-amplitude convective flow. The distortion to the k – ω relation has two constituents: one depends on the horizontal component of the convective velocity and has a sign which depends on the sign of ω/k; the other depends on temperature fluctuations and is independent of the sign of ω/k. The magnitude of the distortion is just at the limit of present observational sensitivity. Thus there is reasonable hope that it will be possible to reveal some aspects of the large-scale flow in the solar convection zone

Temporal Variation of Large Scale Flows in the Solar Interior

2000 ◽  
Vol 179 ◽  
pp. 353-356
Author(s):  
Sarbani Basu ◽  
H. M. Antia
Keyword(s):  
Large Scale ◽  
Outer Part ◽  
Temporal Variations ◽  
Solar Interior ◽  
Short Term ◽  
Measured Velocity ◽  
Solar Convection Zone ◽  
Solar Convection ◽  
Doppler Imager ◽  
Ring Diagram

AbstractWe attempt to detect short-term temporal variations in the rotation rate and other large scale velocity fields in the outer part of the solar convection zone using the ring diagram technique applied to Michelson Doppler Imager (MDI) data. The measured velocity field shows variations by about 10m/s on the scale of few days.

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