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Topic: Convection zone


In the News (Thu 18 Apr 19)

  
  Convective overshoot - Wikipedia, the free encyclopedia
Convective overshoot is the phenomenon of convection carrying material beyond an unstable region of the atmosphere into a stratified, stable region.
Another example of convective overshoot is at the base of the convection zone in the solar interior.
The heat of the Sun's thermonuclear fusion is carried outward by radiation in the deep interior radiative zone and by convective circulation in the outer convection zone, but cool sinking material from the surface penetrates farther into the radiative zone than naive theory would suggest.
en.wikipedia.org /wiki/Convective_overshoot   (248 words)

  
 Helioseismology - Wikipedia, the free encyclopedia
Solar pressure waves are generated by the turbulence in the convection zone, near the surface of the sun, and certain frequencies are amplified by constructive interference.
In the solar convection zone, the temperature gradient is slightly greater than the adiabatic lapse rate, so that there is an anti-restoring force (that drives convection) and g-modes cannot propagate.
The g-modes are evanescent through the entire convection zone, and are thought to have residual amplitudes of only millimeters at the photosphere.
en.wikipedia.org /wiki/Helioseismology   (785 words)

  
 THE CONVECTION ZONE
The convection zone is the outer-most layer of the interior.
The temperature at the bottom of the convection zone is 200,000° C. At the same time the top of the convection zone (surface of the Sun) is being cooled by the creation of light.
The interaction of the convective turbulent motions of the gas in the convection zone and the differential rotation leads to the generation of electric currents and solar magnetic fields.
www.cora.nwra.com /~werne/eos/text/convection_zone.html   (3366 words)

  
 NASA/Marshall Solar Physics
The radiative zone extends outward from the outer edge of the core to the interface layer or tachocline at the base of the convection zone (from 25% of the distance to the surface to 70% of that distance).
The convection zone is the outer-most layer of the solar interior.
Convection occurs when the temperature gradient (the rate at which the temperature falls with height or radius) gets larger than the adiabatic gradient (the rate at which the temperature would fall if a volume of material were moved higher without adding heat).
solarscience.msfc.nasa.gov /interior.shtml   (897 words)

  
 Genesis : Search for Origins | JPL | NASA
From the core outward, these layers are called: the radiative layer (or zone), the convection layer, and the photosphere, which is the surface layer we observe.
At the surface between the convection layer and the photosphere, the gas is very turbulent, rising up in the center of structures called convection cells (supergranules), flowing to the cell boundaries and then sinking.
Above the convection zone is the photosphere, the visible bright surface of the sun.
www.genesismission.org /science/mod3_SunlightSolarHeat/SolarStructure   (1998 words)

  
 NASA CAN at UofC: Annual Report 98
It is well established that turbulent motions in the convective region of the sun are largely responsible for the observed structure and evolution of the solar magnetic activity.
A plausible scenario for solar dynamo action is that the large-scale organized toroidal magnetic field is generated by the action of strong radial shear at the base of the solar convection zone, whereas the weaker poloidal field is regenerated by cyclonic convection throughout the convection zone.
A layer of magnetic field initially placed in the convection zone is swept down by strong sinking plumes, locally amplified, and deposited in the stable region at the base of the convection zone, despite the opposing action of magnetic buoyancy.
astro.uchicago.edu /Computing/HPCC/Report98/milestone8.htm   (4647 words)

  
 [No title]   (Site not responding. Last check: 2007-10-25)
Descriptions of the investigations of flows in the solar convection zone associated with the solar magnetic cycle, and the peculiar periodic variations in rotation near the base of the convection zone, bring the book essentially up to date.
As discussed by Zirker, helioseismic determinations of solar internal rotation were not consistent with initial numerical models that had attempted to describe the dynamics of the solar convection zone and the origin of the variation of the solar surface rotation rate with latitude on the Sun.
Also, more sophisticated models of the interaction between convection and rotation, which better capture the turbulent nature of the flow, are beginning to yield results in accordance with the helioseismic inferences.
www.nature.com /news/2004/040105/pf/427103a_pf.html   (994 words)

  
 HAO Annual Scientific Report 2004
If a non-adiabatic convection zone is considered, then roughly the lower 40-50% of the convection zone is required to be sub-adiabatic (due to non-local convection effects), otherwise additional effects like anisotropic heat transport are needed to explain the observed differential rotation.
It is believed that the magnetic buoyancy instability is responsible for the transport of newly generated toroidal flux from the tachocline to the convection zone (Parker 1955), and that the magnetic pumping mechanism returns the poloidal field to the tachocline for the cycle to repeat.
Of particular interest is the rotation rate near the tachocline, the transition zone between the solid rotation of the radiative interior and the differential rotation of the convection zone.
www.asr.ucar.edu /2004/HAO/siv.html   (8202 words)

  
 convection   (Site not responding. Last check: 2007-10-25)
From the edge of the core outward, first through the radiative and then through the convective zone, the temperature decreases from 8 million to 7,000 K, and density decreases from 20 gm/ cm 3 to 4 x l0 -7 gm/ m 3.
The convection zone is farther away from the core than the the radiative zone.
Energy is carried from the bottom of the convection zone by this motion.
www.wsd1.org /earlgrey/Sun/convection.htm   (420 words)

  
 Solar MHD Group at MPS
The interaction of convective flows and magnetic fields in the solar photosphere and the upper layers of the convection zone is crucial for many phenomena of solar activity.
The magnetic flux is dispersed by supergranular convective motions and meridional circulation.
Structure of the magnetic field in the lower convection zone, M. Schüssler, M. Rempel, in A. Wilson (ed.): "From Solar Min to Max: Half a Solar Cycle with SOHO", SOHO 11 Symposium, ESA SP-508, European Space Agency, p.
www.mps.mpg.de /projects/solar-mhd/research.html   (2332 words)

  
 Convection Zone Modeling
Of particular interest in this regard are the layers immediately above and below the interface between the convective and radiative portions of the solar interior, a region in which, according to helioseismic measurements, significant radial shear exists.
However, in the uppermost layers of the solar convection zone (i.e., extending from the photosphere down to a Rosseland mean optical depth of about 20) the diffusive flux can differ from the radiative flux obtained from a formal solution of the transfer equation (assuming LTE) by as much as 10%.
Consequently, to the extent to which the diffusion approximation inaccurately represents the radiation field near the top of the convection zone, the physical properties of this region can be in error.
web.hao.ucar.edu /public/asr/asr95/convection.html   (736 words)

  
 Astronomy/The Sun - Wikibooks, collection of open-content textbooks
Outside the radiation zone and interface region is a convection zone.
This zone sits between the heated radiation zone and the cooler outer layers of the sun.
The base of the convection zone is at about 2 megakelvins, while material at the very top is at roughly 6000 kelvins.
en.wikibooks.org /wiki/The_Sun   (1207 words)

  
 ssystem
The radiation zone is cooler than the core, about 2.5 million degrees C (4.5 million degrees F).
In the convection zone, churning motions of the gases carry the sun’s energy further outward.
The convection zone is slightly cooler, about 2 million degrees C (1.1 million degrees F), and less dense, about one-tenth as dense as water.
members.tripod.com /~DrGrizzly/ssystem.htm   (832 words)

  
 Solar System: The Sun
The convection zone is the outermost layer of the Sun's interior.
Energy from the core moves through this zone through the process of convection (you may have seen this same process in a pot of boiling water).
The convection zone is cooler than the radiative zone, and at these cooler temperatures, atoms do not give off energy so readily.
www.onr.navy.mil /focus/spacesciences/solarsystem/sun2.htm   (913 words)

  
 Convective Zone   (Site not responding. Last check: 2007-10-25)
This new method of transport is required because outside of the radiation zone the temperature is relatively cool, now only 2 million degrees Kelvin as opposed to 5 million in the radiation zone.
The most efficient means of energy transfer is now convection and we find ourselves in the region of the Sun's interior know as the convection zone.
The hot material follows a direct path through the convective zone and the energy is transferred much faster than it is by radiation.
solar.physics.montana.edu /YPOP/Spotlight/SunInfo/Conzone.html   (246 words)

  
 5 Discussion   (Site not responding. Last check: 2007-10-25)
Such speeds may be sufficient to overcome the magnetic buoyancy of flux generated in the convection zone and transport the flux downward into the overshoot layer.
We should stress however that it cannot be decided from the present simulations whether the large-scale magnetic field of solar-type stars is generated by the convective alpha effect investigated here or by a different alpha effect such as that resulting from the buoyancy instability of magnetic flux tubes in the overshoot layer.
We confirm that the convective alpha effect is strongest near the poles.
www.edpsciences.org /articles/aa/abs/2002/41/aa2379/node5.html   (1502 words)

  
 Study Guide to Section 2
The second section of the course is concerned with a treatment of the convection zone, which resides beneath the visible surface of the Sun.
The dynamic processes that take place in the convection zone are believed to play an extremely important role in shaping the characteristics of this field at it rises and then bursts through the solar surface.
You should however be familiar with the notion that close to the surface of the convection zone a marked change in behaviour gives rise to superadiabaticity: be able to argue the reasons for why this occurs.
bison.ph.bham.ac.uk /~wjc/Teaching/AOSstudII.htm   (806 words)

  
 Solar physics
The sun's three major zones are the core (where nuclear reactions generate energy), the radiative zone (where energy travels outward by radiation), and the convection zone (where convection currents move energy to the surface).
The convective zone, in turn, acts like molasses boiling in a moonshiner's kettle: The hotter fluid rises to the surface and the cooler fluid sinks back down to be reheated.
These convection cells, as they are called, are about as big as Texas in area, but they're hotter than XXX Southwestern Special chili sauce.
whyfiles.org /115sun/3.html   (721 words)

  
 Sunspot - Solar Interior   (Site not responding. Last check: 2007-10-25)
This energy diffuses outward by radiation (mostly gamma-rays and x-rays) through the radiative zone and by convective fluid flows (boiling motion) through the outermost convection zone.
The thin interface layer between the radiative zone and the convection zone is where the Sun's magnetic field is thought to be generated.
At the visible surface the temperature has dropped to 5,700° C and the density is only 0.0000002 gm/cm³ (about 1/10,000th the density of air at sea level).
members.rediff.com /AbhinAru/interior.htm   (882 words)

  
 UCR Space Physics
Because the Sun is heated at the core, we expect the temperature to decrease as we move outwards and, indeed, this is what happens, until we reach the photosphere, which is the visible surface of the Sun.
Beyond the Transition Zone, in the corona, the gas is so hot that atoms lose electrons and the gas becomes a collection of distinct protons, electrons, and some other nuclei.
Cyclonic convection then returns the field lines to their north-south path, but the polarity is reversed.
spacephysics.ucr.edu /index.php?content=solar_wind/sw/sw1.html   (1224 words)

  
 Solar incognita: Scientists map unexplored part of sun's interior   (Site not responding. Last check: 2007-10-25)
The convection zone lies directly beneath the photosphere, which forms the sun's visible surface and effectively hides what is below.
As a result, very little is known about the convection zone's internal structure, despite the fact that it is the source of sunspots, solar flares and most other forms of solar activity that affect Earth.
Finally, there is the convection zone, where the sun's gases boil much like water in a pot on the stove, forming giant cells of rising and falling gases that carry heat to the surface.
www.stanford.edu /dept/news/relaged/960611solarmap.html   (1022 words)

  
 Modelling Astrophysical Turbulent Convection
Turning to the sun, we expect that the largest-scale turbulent flows deep within the convection zone should possess scales comparable to the overall depth of that zone (occupying the outer 30 percent by radius, or about 200,000km in depth).
The results shown in Figure 4 are extraordinary, implying that throughout the turbulent layer nearly all the convective flux is carried by the upflowing material and not the downflows, despite the fact that the downflows are much more coherent in space and time compared to the random fluctuations of the smaller scale upflows.
The convective flux is shown only in the downflows (the upflows are obscured with a grey mask) with fl marking regions of positive convective flux and white marking regions of negative flux.
www.adass.org /adass/proceedings/adass94/brummelln.html   (3571 words)

  
 Stanford SOLAR Center -- Ask A Solar Physicist FAQs - Answer
Apart from that, magnetic field lines in the bottom of the convective zone are lifted up (or drawn down) and twisted by the convective flows (the twist is a result of the Coriolis force action).
In the convective zone, the magnetic field of this erupted flux tube is mostly vertical (see, eg [3] for a discussion of the shape of magnetic flux tube in the convective zone).
The examples of the axisymmetric numerical simulations showing direction of the magnetic field in the convection zone as well as its evolution may be found in [7,8].
solar-center.stanford.edu /FAQ/Qmagstruct.html   (950 words)

  
 National Partnership for Advanced Computational Infrastructure: Archives
Helioseismology, the study of acoustic waves of the deep interior that are detectable at the surface, has revealed that such differential rotation cuts down through the layer, terminating at the base of the convection zone in a shear layer called the tachocline.
In particular, he and his group are interested in the convection zone of intense turbulence, and in the tachocline of shear that separates it from the deeper radiative interior.
In another paper accepted for publication by the Astrophysical Journal, Toomre and Brun report that their simulations of turbulent convection under the influence of rotation closely match helioseismic pictures of the differential rotation within the bulk of the convection zone.
www.npaci.edu /enVision/v17.4/solar.html   (1175 words)

  
 Thesis -- Chapter I, section 3
The cyclic solar magnetic field is thought to originate from a dynamo process in the convection zone of the Sun.
The convection zone is the layer directly below the surface where turbulent motions are responsible for the transport of energy towards the surface.
The origin of the turbulence is the high opacity of the gas in the convection zone which inhibits energy transfer by radiation.
www.xs4all.nl /~josvg/thesis/chap13.html   (1037 words)

  
 The pulse of the solar dynamo
The tachocline -- a region where the rotatation rate changes from differential rotation in the convection zone to nearly solid-body rotation in the interior, is evident near the base of the convection zone, determined to be at radius 0.71 R (where R is the overall solar radius).
The intense turbulence within the solar convection zone excites millions of acoustic oscillation modes of the interior that are observable at the solar surface.
Further, at the base of this convective envelope is the tachocline of strong shear in which the differential rotation with latitude is forced to adjust to the nearly uniform rotation of the deeper radiative interior.
soi.stanford.edu /press/GONG_MDI_03-00   (1741 words)

  
 Dynamics of Solar Magnetoconvection
Volumes of moving hot gas transfer energy to the top of the convection zone where it is released in the form of radiation.
Convection is responsible for most of the phenomena occurring on the otherwise bland surface of the sun.
There are many different balances of forces and energies operating within the convection zone, such as this combination of fluid flow and magnetic pressure exerted within sunspots, that influence the behavior of the sun's outer layers.
www.tc.cornell.edu /~slantz/SPUR/SPUR96/Cynthia/report.html   (3427 words)

  
 Convective Zone
In the convective zone, the energy is transferred much faster than it is in the radiative zone.
It can do this because the convective zone is cooler than the radiative zone and therefore less dense.
The combination of what takes place in the convection zone and the differential rotation of the Sun creates something called the solar dynamo.
solar-heliospheric.engin.umich.edu /hjenning/ConvectiveZone.html   (303 words)

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