Title: Mesoscale Modeling of Impact Compaction of Primitive Solar System Solids Show Chinese title

Title: 中尺度模型对原始太阳系固体的冲击压实

Abstract: We have developed a method for simulating the mesoscale compaction of early solar system solids in low velocity impact events, using the iSALE shock physics code. Chondrules are represented by nonporous disks, placed within a porous matrix. By simulating impacts into bimodal mixtures over a wide range of parameter space (including the chondrule-to-matrix ratio, the matrix porosity and composition and the impact velocity), we have shown how each of these parameters influences the shock processing of heterogeneous materials. The temperature after shock processing shows a strong dichotomy: matrix temperatures are elevated much higher than the chondrules, which remain largely cold. Chondrules can protect some matrix from shock compaction, with shadow regions in the lee side of chondrules exhibiting higher porosity that elsewhere in the matrix. Using the results from this mesoscale modelling, we show how the $\varepsilon-\alpha$ porous compaction model parameters depend on initial bulk porosity. We also show that the timescale for the temperature dichotomy to equilibrate is highly dependent on the porosity of the matrix after the shock, and will be on the order of seconds for matrix porosities of less than 0.1, and on the order of 10's to 100's seconds for matrix porosities of $\sim$ 0.3--0.5. Finally, we have shown that the composition of the post-shock material is able to match the bulk porosity and chondrule-to-matrix ratios of meteorite groups such as carbonaceous chondrites and unequilibrated ordinary chondrites. Show Chinese abstract

Abstract: 我们开发了一种方法，用于在低速撞击事件中模拟早期太阳系固体的介观尺度压实，使用iSALE冲击物理代码。 球粒被表示为无孔隙的圆盘，放置在多孔基质中。 通过在广泛的参数空间（包括球粒与基质的比例、基质孔隙度和成分以及撞击速度）中模拟撞击，我们展示了这些参数如何影响非均质材料的冲击处理。 冲击处理后的温度表现出明显的二分性：基质温度显著高于球粒，球粒则基本保持低温。 球粒可以保护部分基质免受冲击压实，球粒背风侧的阴影区域表现出比基质其他部位更高的孔隙度。 利用这种介观尺度建模的结果，我们展示了$\varepsilon-\alpha$孔隙压实模型参数如何依赖于初始总体孔隙度。 我们还表明，温度二分性的平衡时间高度依赖于冲击后基质的孔隙度，在基质孔隙度小于0.1时约为几秒，而在基质孔隙度为$\sim$0.3--0.5时则约为十几秒到几百秒。 最后，我们证明了冲击后物质的成分能够匹配碳质球粒陨石和未平衡普通球粒陨石等陨石类别的总体孔隙度和球粒与基质比例。