Using solar p-modes to determine the convection zone depth and constrain diffusion-produced composition gradients

1993 ◽  
Vol 411 ◽  
pp. 394 ◽  
Author(s):  
Joyce A. Guzik ◽  
Arthur N. Cox
Keyword(s):  
Convection Zone ◽  
Zone Depth ◽  
Composition Gradients

scholarly journals Fractional Stellar Convection Zone Depth and the Generation of Magnetic Flux: An Empirical Approach

1983 ◽  
Vol 102 ◽  
pp. 187-192
Author(s):  
Mark S. Giampapa
Keyword(s):  
Magnetic Flux ◽  
Convection Zone ◽  
Line Emission ◽  
Dwarf Stars ◽  
Preliminary Results ◽  
Telescope Facility ◽  
Zone Depth ◽  
M Dwarf Stars ◽  
M Dwarf ◽  
Mirror Telescope

I present preliminary results from an observational investigation of very late M dwarf stars utilizing the Multiple Mirror Telescope facility. I find that dwarf stars later than spectral type M5 do not necessarily exhibit Hα line emission, contrary to the assertion by Joy and Abt (1974). The preliminary results I discuss herein tentatively suggest, but do not prove, that the generation of significant magnetic fields and magnetic flux is severely inhibited in fully convective stars.

scholarly journals Element Diffusion in Pulsating Variables

1993 ◽  
Vol 139 ◽  
pp. 243-251
Author(s):  
Joyce Ann Guzik
Keyword(s):  
Convection Zone ◽  
Diffusion Theory ◽  
Shallow Convection ◽  
Element Diffusion ◽  
Yield Information ◽  
Intermediate Degree ◽  
Composition Gradients ◽  
High Degree ◽  
Scuti Stars ◽  
Δ Scuti Stars

AbstractCan pulsation studies yield information on the operation of element diffusion in stars? Can diffusion explain unusual properties of pulsating variables? Element diffusion theory and recent research relevant to these questions will be reviewed, with emphasis on the Sun and δ Scuti stars. High-degree solar p-modes that are sensitive to helium ionization support a reduced convection zone helium abundance consistent with that expected from diffusion. Intermediate-degree p-modes can be used to probe the structure of the convection zone base and constrain possible diffusion-produced composition gradients. δ Scuti variables have shallow convection zones and relatively short diffusion timescales. Helium diffusion may explain unusual period ratios, influence period changes, and affect the amplitudes and light curve shapes of δ Scuti stars.

Predictive convection zone depth of chloride in concrete under chloride environment

2016 ◽  
Vol 72 ◽  
pp. 257-267 ◽  
Author(s):  
Peng Liu ◽  
Zhiwu Yu ◽  
Zhaohui Lu ◽  
Ying Chen ◽  
Xiaojie Liu
Keyword(s):  
Convection Zone ◽  
Zone Depth ◽  
Chloride Environment

Fossil fields in early stellar evolution

2008 ◽  
Vol 4 (S259) ◽  
pp. 443-444
Author(s):  
Rainer Arlt
Keyword(s):  
Magnetic Fields ◽  
Stellar Evolution ◽  
Time Scale ◽  
Convection Zone ◽  
Evolutionary Time ◽  
Evolutionary Time Scale ◽  
Zone Depth

AbstractFavored explanations for the presence of magnetic fields on CP stars and the presence of the solar tachocline below the convection zone both imply fossil magnetic fields in the radiative zones. The initial, convective evolution of magnetic fields in a proto-star is studied by numerical, global simulations. The computations are to be extended by a change of the convection zone depth on an evolutionary time-scale.

scholarly journals The First Theoretical γ Doradus Instability Strip

2004 ◽  
Vol 193 ◽  
pp. 474-477
Author(s):  
Anthony B. Kaye ◽  
Phillip B. Warner ◽  
Joyce A. Guzik
Keyword(s):  
Convection Zone ◽  
Instability Strip ◽  
Zone Depth

AbstractWe present the first theoretical γ Doradus instability strip. We find that our model instability strip agrees very well with the previously established, observationally based, instability strip of Handler & Shobbrook (2002). We stress, as in Guzik et al. (2000), that the convection zone depth plays the major role in the determination of our instability strip. Once this depth becomes too deep or too shallow, the convection zone no longer allows for pulsational instability.

scholarly journals Helioseismology

1995 ◽  
Vol 155 ◽  
pp. 98-108
Author(s):  
Ronald L. Gilliland
Keyword(s):  
Convection Zone ◽  
Surface Structures ◽  
Stellar Structure ◽  
Helium Abundance ◽  
Interior Structure ◽  
Evolution Theory ◽  
Near Surface ◽  
History Of ◽  
Zone Depth ◽  
The Stability

AbstractObservations of solar p-mode oscillations over the last two decades have provided a fundamentally new and unique means of probing the Sun’s interior structure. The history of understanding solar oscillations as trapped normal-mode pulsations will be briefly discussed. The large number of excited modes seen in the Sun have been used to constrain the solar core structure, determine the convection zone depth and to fix the variation of angular velocity with depth and latitude. Standard stellar structure and evolution theory does remarkably well in matching the helioseismic results. Further work promises to reveal the solar helium abundance. Upcoming network and space observations should provide the stability and resolution necessary to return detailed information on near-surface structures associated with solar activity.

Alpha-Effect, Current and Kinetic Helicities for Magnetically Driven Turbulence, and Solar Dynamo

2000 ◽  
Vol 179 ◽  
pp. 387-388
Author(s):  
Gaetano Belvedere ◽  
V. V. Pipin ◽  
G. Rüdiger
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Convection Zone ◽  
Solar Surface ◽  
Momentum Transport ◽  
Angular Momentum Transport ◽  
Magnetic Buoyancy ◽  
Alpha Effect ◽  
Current Helicity

Extended AbstractRecent numerical simulations lead to the result that turbulence is much more magnetically driven than believed. In particular the role ofmagnetic buoyancyappears quite important for the generation ofα-effect and angular momentum transport (Brandenburg & Schmitt 1998). We present results obtained for a turbulence field driven by a (given) Lorentz force in a non-stratified but rotating convection zone. The main result confirms the numerical findings of Brandenburg & Schmitt that in the northern hemisphere theα-effect and the kinetic helicityℋkin= 〈u′ · rotu′〉 are positive (and negative in the northern hemisphere), this being just opposite to what occurs for the current helicityℋcurr= 〈j′ ·B′〉, which is negative in the northern hemisphere (and positive in the southern hemisphere). There has been an increasing number of papers presenting observations of current helicity at the solar surface, all showing that it isnegativein the northern hemisphere and positive in the southern hemisphere (see Rüdigeret al. 2000, also for a review).

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