=== GFD オンラインセミナー 第 12 回

* 日時: 

  2024 年 2 月 8 日 (木) 15:00 - 17:00

* 話題提供者とタイトル

  Prof. Stephane Labrosse (ENS Lyon, France)

  「Convection in solids with melting and freezing at either or both boundaries」

* 共催

  CPS (神戸大学惑星科学研究センター) セミナー 

* 要旨:

  Thermal convection is the main heat transfer mechanism in the interiors of large planetary objects, in their solid layers as well as the liquid and gaseous ones. The best known example of such a convecting solid layer is the Earth’s mantle which deforms viscously on million years’ time scale, arocess which surface expression is plate tectonics. In many instances, the solid layer undergoing convection is bounded above or below, and possibly both, by a liquid layer with a phase equilibrium relationship at the boundary. This has been the case in the early stages of rocky planets, when magma ocean was still crystallizing, and it is currently the case for icy satellites of Saturn and Jupiter and possibly in Earth’s inner core. The possibility of changing phaseat a boundary has profound implications for the dynamics of the solid: solid matter flowing toward the boundary can cross it by melting and, conversely, matter can enter the solid in places of freezing. This process can be included in convection models by replacing the classical no-penetration boundary condition by a phase change boundary condition parameterized by a phase change number comparing the timescale needed to erase the topography of the boundary to the one needed to generate it viscously. The implications of this boundary condition are profound, for the linear onset of convection as well as for fully non-linear solutions, making convection much more easy and efficient. In my seminar, I will present the general theory, the linear stability in cartesian and spherical shell geometry, non-linear results in cartesian and spherical shell geometry and implications for the dynamics of high pressure ice layers in large icy satellites. I will also present a model for the evolution of the Earth’s mantle with a crystallizing basal magma ocean.