Viscous dissipation as a mechanism for spatiotemporal chaos in Rayleigh-Bénard convection between poorly conducting boundaries at infinite Prandtl number

Nonlinear Rayleigh-Bénard convection in an infinite-Prandtl-number fluid layer between poorly conducting boundaries is considered as a model for convection in the earth's upper mantle. It is shown that accounting for the generally neglected impact of viscous dissipation may lead to the development of large-scale spatiotemporal chaotic dynamics governed by the familiar Kuramoto-Sivashinsky equation φτ+?4φ+2?2φ-(?φ)2+αφ=0, known to occur in various physical systems.