Confined states in large-aspect-ratio thermosolutal convection

Spina, Alejandro; Toomre, J.; Knobloch, Edgar

doi:10.1103/physreve.57.524

Cited by 30 publications

(30 citation statements)

References 44 publications

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“…44 We mention that different types of localized waves, nonlinear compression waves traveling on a background of traveling waves, have also been identified in doubly diffusive convection. 45 We have also found structures of source and sink type. Sources are localized structures that emit waves, while sinks arise at locations, where waves traveling in opposite directions collide.…”

Section: -10mentioning

confidence: 71%

Homoclinic snaking of localized states in doubly diffusive convection

2011

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Numerical continuation is used to investigate stationary spatially localized states in two-dimensional thermosolutal convection in a plane horizontal layer with no-slip boundary conditions at top and bottom. Convectons in the form of 1-pulse and 2-pulse states of both odd and even parity exhibit homoclinic snaking in a common Rayleigh number regime. In contrast to similar states in binary fluid convection, odd parity convectons do not pump concentration horizontally. Stable but time-dependent localized structures are present for Rayleigh numbers below the snaking region for stationary convectons. The computations are carried out for (inverse) Lewis number s ¼ 1=15 and Prandtl numbers Pr ¼ 1 and Pr )

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Section: -10mentioning

confidence: 71%

Homoclinic snaking of localized states in doubly diffusive convection

2011

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“…This speed differs in general from the speed of a single pulse. All of these states form close to the parameter values at which the primary homoclinic orbit is present [9, 11] and have similar speeds. In contrast, there are also spatially extended states (hereafter infinite pulse trains) consisting of copies of the single pulse state, in which each pulse is locked to the oscillatory tail of the preceding pulse [10, 14].…”

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confidence: 79%

Generation of finite wave trains in excitable media

et al. 2008

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Spatiotemporal control of excitable media is of paramount importance in the development of new applications, ranging from biology to physics. To this end, we identify and describe a qualitative property of excitable media that enables us to generate a sequence of traveling pulses of any desired length, using a one-time initial stimulus. The wave trains are produced by a transient pacemaker generated by a one-time suitably tailored spatially localized finite amplitude stimulus, and belong to a family of fast pulse trains. A second family, of slow pulse trains, is also present. The latter are created through a clumping instability of a traveling wave state (in an excitable regime) and are inaccessible to single localized stimuli of the type we use. The results indicate that the presence of a large multiplicity of stable, accessible, multi-pulse states is a general property of simple models of excitable media.

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“…The emergence of spatially localized convective states has been observed in other systems, particularly in theoretical studies of doubly diffusive systems such as thermosolutal convection (e.g., Spina et al 1998;Batiste et al 2006), in laboratory studies of convection in binary fluids (e.g., Surko et al 1991), and in simulations of magnetoconvection where isolated ''convectons'' have been observed (Blanchflower 1999). In shells of rapidly rotating fluid, temporally intermittent patches of localized convection emerged in Boussinesq simulations of the geodynamo (Grote & Busse 2000).…”

Section: Convection Rotation and Magnetismmentioning

confidence: 94%

Rapidly Rotating Suns and Active Nests of Convection

Brown

Browning

Brun

et al. 2008

Astrophysical Journal

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139

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In the solar convection zone, rotation couples with intensely turbulent convection to drive a strong differential rotation and achieve complex magnetic dynamo action. Our Sun must have rotated more rapidly in its past, as is suggested by observations of many rapidly rotating young solar-type stars. Here we explore the effects of more rapid rotation on the global-scale patterns of convection in such stars and the flows of differential rotation and meridional circulation, which are self-consistently established. The convection in these systems is richly time-dependent, and in our most rapidly rotating suns a striking pattern of localized convection emerges. Convection near the equator in these systems is dominated by one or two nests in longitude of locally enhanced convection, with quiescent streaming flow in between them at the highest rotation rates. These active nests of convection maintain a strong differential rotation despite their small size. The structure of differential rotation is similar in all of our more rapidly rotating suns, with fast equators and slower poles. We find that the total shear in differential rotation Á grows with more rapid rotation, while the relative shear Á/ 0 decreases. In contrast, at more rapid rotation, the meridional circulations decrease in energy and peak velocities and break into multiple cells of circulation in both radius and latitude. Subject headingg s: convection -stars: interiors -stars: rotation -Sun: interior -Sun: rotation CONVECTION, ROTATION, AND MAGNETISMOur Sun is a magnetic star whose cycles of magnetic activity must arise from organized dynamo action in its interior. This dynamo action is achieved by turbulent plasma motions in the solar convection zone, which spans the outer 29% of the Sun in radius. Here vigorous convective motions and rotation couple to drive the differential rotation and meridional circulation. These globalscale flows are important ingredients in stellar dynamo theory, providing shear, which may build and organize fields on global scales. When our Sun was younger, it must have rotated much more rapidly, as is suggested both by the solar wind, which continually removes angular momentum from the Sun, and by many observations of rapidly rotating solar-like stars. In more rapidly rotating suns the coupling between rotation and convection is strong and must continue to drive global scales of flow. Understanding the nature of convection, differential rotation, and meridional circulation in more rapidly rotating stars is a crucial step toward understanding stellar dynamos.The manner in which the Sun achieves global-scale dynamo action is gradually being sorted out. Helioseismology, which uses acoustic oscillations to probe the radial structure of the star, as well as the convective flows beneath the surface, has revealed that the solar differential rotation profile observed at the surface prints throughout the convection zone, with two prominent regions of radial shear. The near-surface shear layer occupies the outer 5% of the Sun, where...

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Confined states in large-aspect-ratio thermosolutal convection

Cited by 30 publications

References 44 publications

Homoclinic snaking of localized states in doubly diffusive convection

Homoclinic snaking of localized states in doubly diffusive convection

Generation of finite wave trains in excitable media

Rapidly Rotating Suns and Active Nests of Convection

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