scholarly journals Convection in the Sun

1990 ◽  
Vol 121 ◽  
pp. 101-115
Author(s):  
Josep M. Massaguer
Keyword(s):  
Large Scale ◽  
Laboratory Experiments ◽  
Convection Zone ◽  
Planar Geometry ◽  
Hydrodynamic Models ◽  
Solar Convection Zone ◽  
Large Scale Structures ◽  
Solar Convection ◽  
Non Local ◽  
Scale Structures

AbstractThe present knowledge of the dynamics and structure of the solar convection zone is reviewed with the aim of checking current assumptions and conjectures against laboratory experiments and numerical modeling of thermal convection. Buoyancy is the only forcing considered. Rotation and magnetic fields are explicitly avoided. Nor are departures from planar geometry considered, except as regards large scale structures. Local theories are reviewed in section §2, hydrodynamic models in §3, non-local theories in §4, the global structure of the convection zone is discussed in §5 and the flow patterns in §6.

scholarly journals Convection and Dynamo in Newly Born Neutron Stars

2022 ◽  
Vol 924 (2) ◽  
pp. 75
Author(s):  
Youhei Masada ◽  
Tomoya Takiwaki ◽  
Kei Kotake
Keyword(s):  
Spherical Shell ◽  
Neutron Stars ◽  
Large Scale ◽  
Convection Zone ◽  
Turbulent Transport ◽  
Mean Field ◽  
Magnetic Component ◽  
Large Scale Structures ◽  
Scale Structures ◽  
Convective Model

Abstract To study properties of magnetohydrodynamic (MHD) convection and resultant dynamo activities in proto-neutron stars (PNSs), we construct a “PNS in a box” simulation model and solve the compressible MHD equation coupled with a nuclear equation of state (EOS) and simplified leptonic transport. As a demonstration, we apply it to two types of PNS model with different internal structures: a fully convective model and a spherical-shell convection model. By varying the spin rate of the models, the rotational dependence of convection and the dynamo that operate inside the PNS is investigated. We find that, as a consequence of turbulent transport by rotating stratified convection, large-scale structures of flow and thermodynamic fields are developed in all models. Depending on the spin rate and the depth of the convection zone, various profiles of the large-scale structures are obtained, which can be physically understood as steady-state solutions to the “mean-field” equation of motion. Additionally to those hydrodynamic structures, a large-scale magnetic component of  ( 10 15 ) G is also spontaneously organized in disordered tangled magnetic fields in all models. The higher the spin rate, the stronger the large-scale magnetic component grows. Intriguingly, as an overall trend, the fully convective models have a stronger large-scale magnetic component than that in the spherical-shell convection models. The deeper the convection zone extends, the larger the size of the convective eddies becomes. As a result, rotationally constrained convection seems to be more easily achieved in the fully convective model, resulting in a higher efficiency of the large-scale dynamo there. To gain a better understanding of the origin of the diversity of a neutron star’s magnetic field, we need to study the PNS dynamo in a wider parameter range.

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

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 Large-scale flows and convection at the base of solar convection zone

2006 ◽  
Vol 2 (S239) ◽  
pp. 425-430
Author(s):  
Evgeniy Tikhomolov
Keyword(s):  
Magnetic Fields ◽  
Large Scale ◽  
Convection Zone ◽  
Three Dimensional ◽  
Solar Radius ◽  
Solar Convection Zone ◽  
Solar Convection ◽  
Rotation Periods ◽  
Scale Temperature ◽  
Local Sound

AbstractDevelopment of convection in sun's outer shell is caused by reduction of effectiveness of energy transfer by radiation. Traditionally, models of solar convection are considered to be axisymmetric on the scale of solar radius. Such models provide basic understanding of convection under solar conditions. However, interpretation of a number of observable large-scale long-lived solar phenomena requires developing a non-axisymmetric approach. We present such a model in which large-scale non-axisymmetry is caused by large-scale flows such as Rossby waves and vortices. We model flows near the base of the solar convection zone. Anelastic approximation is used, which is valid for flow velocities much smaller than local sound speed. Our three-dimensional numerical simulations show that interaction of convection with large-scale flows leads to the establishment of non-axisymmetric large-scale temperature distribution. The interaction also gives rise to large-scale variations of penetration depth of convective plumes. Generation of the magnetic field by large-scale non-axisymmetric flows can explain such solar phenomena as complexes of activity, active longitudes, drifts of large-scale magnetic fields from equator to the poles, and appearance of distinct rotation periods of magnetic fields at some latitudes. We discuss a possibility of detection of large-scale non-axisymmetric flows and temperature distributions associated with them by the methods of helioseismology.

scholarly journals Search for Giant Cells in the Solar Convection Zone

1980 ◽  
Vol 91 ◽  
pp. 21-23 ◽  
Author(s):  
B. J. Labonte ◽  
R. Howard
Keyword(s):  
Large Scale ◽  
Convection Zone ◽  
Solar Rotation ◽  
Longitudinal Velocity ◽  
Giant Cells ◽  
Solar Convection Zone ◽  
Solar Convection ◽  
Mount Wilson Observatory ◽  
Entire Dataset ◽  
Full Disk

The Mount Wilson Observatory has obtained daily full disk digital magnetograms of the Sun since 1966, with 12 to 17 arcsecond resolution. As each magnetogram is taken, the position of the Doppler line shift compensator is also recorded, thus giving a full disk map of the longitudinal velocity. This entire dataset is currently being rereduced on a uniform basis (Howard et al., 1980), and daily arrays of residual velocities are being formed by removing large scale patterns, e.g., Earth's motions, solar rotation, limbshift. Data from the years 1972 through 1978 are used here.

Testing Reynolds stress model in solar interior

2006 ◽  
Vol 2 (S239) ◽  
pp. 373-375
Author(s):  
J. Y. Yang ◽  
Y. Li
Keyword(s):  
Reynolds Stress ◽  
Convection Zone ◽  
Reynolds Stress Model ◽  
Solar Interior ◽  
Stress Model ◽  
Solar Convection Zone ◽  
Solar Convection ◽  
Mode Oscillation ◽  
Non Local ◽  
Oscillation Frequencies

AbstractThe Reynolds stress model (RSM) for turbulent convection motion is compared to the MLT in solar model. The free parameters involved in the RSM are also tested with the aid of helioseismology. It is found that, the structure of solar convection zone is differ from the MLT when using the RSM, especially for the Reynolds correlations and the temperature gradient. Both the local and non-local RSM can improve the calculated solar p-mode oscillation frequencies with the appropriate choice of the parameters' value.

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 Pumping of Rossby Waves and Vortices at the Base of the Solar Convection Zone

1998 ◽  
Vol 185 ◽  
pp. 177-178
Author(s):  
Evgeniy Tikhomolov
Keyword(s):  
Large Scale ◽  
Rossby Waves ◽  
Convection Zone ◽  
Polar Field ◽  
Field Reversal ◽  
Solar Convection Zone ◽  
Magnetic Structures ◽  
Solar Convection ◽  
Long Term Behavior

Rossby vortices excited near the base of the solar convection zone are very appealing objects for interpretation of a number of solar phenomena such as long-lived large-scale magnetic structures, the poleward drift of the axisymmetric components after the polar field reversal, and a peculiar long-term behavior of the nonaxisymmetric components (Tikhomolov and Mordvinov 1996).

Sign in / Sign up

Export Citation Format

Share Document