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Figure 2( I a i ) shows the spatio-temporal map of the velocity component Graph $u x$ at Graph $Ra=1.2\times 10^{5}$ recorded by the ultrasonic sensor Graph $Bottom$ at a height of Graph $z = 0.25 H$. According to figure 13, Graph $Nu$ reaches a maximum value at time points Graph $t = 0$ and Graph $t = 0.5\tau {OS}$, while minima occur at Graph $t = 0.25\tau {OS}$ and Graph $t = 0.75\tau {OS}$. Graph $Middle \textit {1}$ and Graph $Middle \textit {2}$ are at the mid-height of the container (Graph $z = 0.5H$) and Graph $Bottom$ is situated close to the bottom plate (Graph $z = 0.25H$). The symbols Graph $g$ and Graph $\Delta T$ denote the gravitational acceleration and the vertical temperature difference in a fluid layer of thickness Graph $H$ and characteristic horizontal dimension Graph $L$. In particular, for a temperature of Graph $25\,^{\circ } \textrm {C}$ the following values are reported: density Graph $\rho = 6360\ \textrm {kg}\ \textrm {m}^{-3}$, thermal expansion coefficient Graph $\alpha = 1.24 \times 10^{-4}\ \textrm {K}^{-1}$, kinematic viscosity Graph $\nu = 3.4 \times 10^{-7}\ \textrm {m}^{2} \ \textrm {s}^{-1}$ and thermal diffusivity Graph $\kappa = 1.03 \times 10^{-5} \textrm {m}^{2}\ \textrm {s}^{-1}$. [Extracted from the article]

We present laboratory measurements of the interaction between thermoelectric currents and turbulent magnetoconvection. In a cylindrical volume of liquid gallium heated from below and cooled from above and subject to a vertical magnetic field, it is found that the large-scale circulation (LSC) can undergo a slow axial precession. Our experiments demonstrate that this LSC precession occurs only when electrically conducting boundary conditions are employed, and that the precession direction reverses when the axial magnetic field direction is flipped. A thermoelectric magnetoconvection (TEMC) model is developed that successfully predicts the zeroth-order magnetoprecession dynamics. Our TEMC magnetoprecession model hinges on thermoelectric current loops at the top and bottom boundaries, which create Lorentz forces that generate horizontal torques on the overturning large-scale circulatory flow. The thermoelectric torques in our model act to drive a precessional motion of the LSC. This model yields precession frequency predictions that are in good agreement with the experimental observations. We postulate that thermoelectric effects in convective flows, long argued to be relevant in liquid metal heat transfer and mixing processes, may also have applications in planetary interior magnetohydrodynamics. [ABSTRACT FROM AUTHOR]