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arXiv 2304.07660physics.geo-ph
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推广混合加热地幔对流的标度律

Generalizing scaling laws for mantle convection with mixed heating

Amy L. Ferrick, Jun Korenaga

AI总结:

针对混合加热地幔对流缺乏可靠热通量参数化的问题,本文提出纳入边界层稳定性及热边界层相互作用的标度方法,解释了地表热通量的局部决定机制。

摘要:

行星地幔中的对流处于所谓的混合加热模式;它既由更热的地核导致的自下而上加热驱动,也由放射性生热和长期冷却导致的内部加热驱动。因此,为了模拟类地行星的热演化,我们尤其需要对混合加热对流的热通量进行参数化。然而,从基本原理导出这样的参数化是一项难以实现的任务。尽管利用热边界层处于边缘稳定状态这一思想,纯内部加热和纯底部加热的标度律已经被成功确定,但近期的理论分析对该思想是否适用于混合加热模式下的对流提出了质疑。在这里,我们提出一种植根于对流物理的标度方法,其中包括边界层稳定性判据。我们表明,只要适当考虑热边界层之间的相互作用,该判据就能成功描述混合加热对流中各热边界层性质之间的关系。对流流体的地表热通量由上部热边界层的性质局部决定,而非全局决定。我们这一基础性标度方法可以方便地推广到行星地幔内几乎任意复杂程度的对流。

英文摘要:

Convection in planetary mantles is in the so-called mixed heating mode; it is driven by heating from below, due to a hotter core, as well as heating from within, due to radiogenic heating and secular cooling. Thus, in order to model the thermal evolution of terrestrial planets, we require the parameterization of heat flux for mixed heated convection in particular. However, deriving such a parameterization from basic principles is an elusive task. While scaling laws for purely internal heating and purely basal heating have been successfully determined using the idea that thermal boundary layers are marginally stable, recent theoretical analyses have questioned the applicability of this idea to convection in the mixed heating mode. Here, we present a scaling approach that is rooted in the physics of convection, including the boundary layer stability criterion. We show that, as long as interactions between thermal boundary layers are properly accounted for, this criterion succeeds in describing relationships between thermal boundary layer properties for mixed heated convection. The surface heat flux of a convecting fluid is locally determined by the properties of the upper thermal boundary layer, as opposed to globally determined. Our foundational scaling approach can be readily extended to nearly any complexity of convection within planetary mantles.

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