The Formation of Planetary Proto-Atmospheres

背景：在它们形成的过程中，原行星变得足够大，可以通过引力将它们诞生的圆盘上的气体结合起来。对于像木星这样的巨行星，岩石或冰核变得如此巨大，以至于引发了失控的气体吸积。而海王星、地球和超级地球等较小的行星只能结合有限数量的气体。因此，盘内阶段气体吸积的物理细节产生了观测到的行星分布的独特属性。方法：利用最先进的辐射-流体动力学模型，研究嵌入在行星盘中的行星原大气的形成和早期演化。在二维和三维模拟中，我们将包括水动力效应和热力学效应。此外，在以行星为中心的球坐标系中，以网格原点的行星为中心，在局部框架中进行这些模拟，使我们能够以非常高的分辨率解决大气积聚的物理问题。代表大规模磁盘流的局部帧的初始条件和边界条件将从先前的全局磁盘模拟中提取出来，这些模拟以网格原点的主星为球坐标进行。目的：我们将提取大气质量，其旋转剖面，辐射冷却以及气体补充时间标度作为核心，磁盘和周围气体和尘埃的光学特性的函数。由此，我们研究了在何种条件下形成的大气接近稳态或准稳态系统。此外，我们可以专门测试这个假设，是否储存在核心的热量和/或气体流动的不对称结构阻止了超级地球的大气坍缩。行星原大气的流体动力学和热力学将在其形成和早期演化的直接高分辨率模型中进行研究。遵循局部方法可以让我们以前所未有的细节确定小尺度物理。这一研究成果将揭示超级地球大气的形成和稳定性。

Context: During their formation, proto-planets become massive enough to gravitationally bind gas from the disks they are born in. For giant planets such as Jupiter, the rocky or icy core becomes so massive that it triggers a runaway accretion of gas. Smaller planets such as Neptune, Earth, and super-Earths instead are only able to bind a limited amount of gas. Hence, the physical details of gas accretion in the disk-embedded phase yields a distinctive attribute of the observed planetary distribution.Methods: The formation and early evolution of planetary proto-atmospheres, embedded in their natal disk, shall be investigated using state-of-the-art radiation-hydrodynamical modeling. We will include both - the hydrodynamic as well as the thermodynamic - effects in two- and three-dimensional simulations. Moreover, conducting these simulations in a local frame in planeto-centric spherical coordinates with the planet at the origin of the grid, allows us to resolve the physics of the atmospheric build-up in very high resolution. Initial and boundary conditions for the local frame, representing the large-scale disk flow, will be extracted from preceding global disk simulations, performed in spherical coordinates with the host star at the origin of the grid.Aims: We will extract the atmospheric mass, its rotation profile, and the radiative cooling as well as the gas replenishing timescale as a function of the core, the disk, and the optical properties of the surrounding gas and dust. From that, we investigate under which condition the forming atmosphere approaches a steady state or quasi-stationary system. Additionally, we can specifically test the hypothesis, whether the thermal heat stored in the core and/or the asymmetric structure of the gas flow prevents the atmospheres of super-Earths from collapsing. Resume: The hydrodynamics and thermodynamics of planetary proto-atmospheres will be investigated in direct high-resolution modeling of their formation and early evolution. Following a local approach allows us to determine the small-scale physics in unprecedented detail. The research outcome will shed light on the formation and stability of super-Earth atmospheres.