On thermal interaction between the Earth's core and mantle: An annular channel model

Core-mantle thermal interaction has long been recognized as having a critical influence over the dynamics of the Earth's fluid core and long-term variations of the geomagnetic field. This paper studies the core-mantle thermal coupling by investigating non-linear convection in an annular channel rotating about a vertical axis, heated uniformly from below with heat-flux anomalies on its sidewalls. In the absence of the heat-flux anomalies, convection is characterized by two steady travelling waves: one in the vicinity of the outer wall propagates against the sense of rotation and the other near the inner wall propagates in the same sense as rotation. In the presence of the heat-flux anomalies, however, non-linear convection either exhibits complete locking onto the corresponding lateral heterogeneity on the sidewall or becomes strongly time-dependent, interspersed with the intervals of nearly no fluid motions. Implications of the results for the core convection and geodynamo are discussed.