The onset of thermo-compositional convection in rotating spherical shells

Silva, L. A.C. , Mather, J. F. and Simitev, R. D. (2019) The onset of thermo-compositional convection in rotating spherical shells. Geophysical and Astrophysical Fluid Dynamics, 113(4), pp. 377-404. (doi: 10.1080/03091929.2019.1640875)

Abstract

Double-diffusive convection driven by both thermal and compositional buoyancy in a rotating spherical shell can exhibit a rather large number of behaviours often distinct from that of the single diffusive system. In order to understand how the differences in thermal and compositional molecular diffusivities determine the dynamics of thermo-compositional convection we investigate numerically the linear onset of convective instability in a double-diffusive setup. We construct an alternative equivalent formulation of the non-dimensional equations where the linearised double-diffusive problem is described by an effective Rayleigh number, Ra, measuring the amplitude of the combined buoyancy driving, and a second parameter, α, measuring the mixing of the thermal and compositional contributions. This formulation is useful in that it allows for the analysis of several limiting cases and reveals dynamical similarities in the parameters space which are not obvious otherwise. We analyse the structure of the critical curves in this Ra−α space, explaining asymptotic behaviours in α, transitions between inertial and diffusive regimes, and transitions between large-scale (fast drift) and small-scale (slow drift) convection. We perform this analysis for a variety of diffusivities, rotation rates and shell aspect ratios showing where and when new modes of convection take place.

• Item Type: Articles
• Additional Information: This work was supported by the Leverhulme Trust [grant number RPG-2012-600].
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Silva, Dr Luis and Simitev, Professor Radostin and Mather, Mr James
• Authors: Silva, L. A.C., Mather, J. F., and Simitev, R. D.
• College/School: College of Science and Engineering > School of Mathematics and Statistics > Mathematics
• Journal Name: Geophysical and Astrophysical Fluid Dynamics
• Publisher: Taylor and Francis
• ISSN: 0309-1929
• ISSN (Online): 1029-0419
• Published Online: 15 July 2019
• Copyright Holders: Copyright © 2019 Taylor and Francis
• First Published: First published in Geophysical and Astrophysical Fluid Dynamics 113(4):377-404
• Publisher Policy: Reproduced in accordance with the publisher copyright policy