Letter to the Editor

Swaying oscillations in Rayleigh-Bénard convection cast new light on solar convection

¹ Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
² Georg-August-Universität Göttingen, Institut für Astrophysik und Geophysik, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
³ Faculty Comp. Sci. and Appl. Mathematics, Univ. of Applied Sciences, Technikum Wien, Höchstädtplatz 6, 1200 Wien, Austria
⁴ Wolfgang-Pauli-Institute c/o Faculty of Mathematics, University of Vienna, Oskar-Morgenstern-Platz 1, 1090 Wien, Austria
⁵ Fakultät für Mathematik, Universität Wien, Oskar-Morgenstern-Platz 1, 1090 Wien, Austria
⁶ Brandenburg University of Technology Cottbus-Senftenberg, Department of Aerodynamics and Fluid Mechanics, Siemens-Halske-Ring 14, 03046 Cottbus, Germany
⁷ Hochschule Mittweida, Fakultät CB, Technikumplatz 17, 09648 Mittweida, Germany
⁸ Center for Astrophysics and Space Science, NYUAD Research Institute, New York University Abu Dhabi, Abu Dhabi, UAE

^⋆ Corresponding authors: friedrich.kupka@technikum-wien.at, Friedrich.Kupka@univie.ac.at

Received: 27 March 2023
Accepted: 22 October 2025

Abstract

Horizontally periodic Boussinesq Rayleigh-Bénard convection (RBC) is a simple model system for studying the formation of large-scale structures in turbulent convective flows. We performed a suite of 2D numerical RBC simulations between no-slip boundaries at different Prandtl (Pr) and Rayleigh (Ra) numbers, such that their product was representative of the upper solar convection zone. When the fluid viscosity was sufficiently low (Pr ≲ 0.1) and turbulence was strong (Ra > 10⁶), large structures began to couple in time and space. For Pr = 0.01, we observed long-lived swaying oscillations of the upflows and downflows that synchronized over multiple convection cells. This new regime of oscillatory convection might offer an interpretation of the wave-like properties of the dominant convection scale on the Sun (supergranulation).