发表机构
Washington State University; Kharkiv Institute of Physics and Technology; Florida State University（华盛顿州立大学; 哈尔科夫物理与技术研究所; 佛罗里达州立大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过拉格朗日示踪粒子分析揭示，Ia型超新星爆燃火焰的热膨胀通过声波压力平衡将内部能量转为热能，预热燃料并显著缩短点火时间，影响范围超过层流火焰厚度。
AI 中文摘要
Ia型超新星中的热核火焰锋面会发展出流体动力学不稳定性，从而产生中尺度湍流流动和显著的局部热力学变化。Brooker等人（2025）的最新研究显示，在瑞利-泰勒不稳定的爆燃锋面附近，燃料点火时间系统性缩短，但其物理起源尚不清楚。我们利用多维模拟和拉格朗日示踪粒子分析，研究了火焰锋面附近燃料的热力学演化，重点关注部分简并碳-氧等离子体中的火焰驱动膨胀和点火时间变异性。示踪轨迹表明，火焰锋面附近被强烈预处理的燃料团（仅占燃料层少数）在低密度和高密度模型之间经历了近似压力约束的膨胀，密度适度降低，温度升高约2×10^8 K至7×10^8 K（较未扰动燃料温度高约13%至63%）。尽管热力学扰动适中，碳点火的强温度敏感性仍导致点火时间大幅缩短。结果表明存在两步机制：火焰热膨胀将燃料扰动至偏离流体静力学平衡，而弱声波恢复压力平衡则将内部能量从简并组分重新分配至热组分。这提高了燃料温度并产生局部热力学预处理。这些结果表明，非稳态热核火焰可缩短火焰前方的点火时间，影响距离超过层流火焰厚度的燃料。由于所分析燃料中核燃烧被禁用，这种预处理是否导致二次点火或促进爆燃向爆轰转变，在本研究中未予测试。
英文摘要
Thermonuclear flame fronts in Type Ia supernovae develop hydrodynamic instabilities that generate turbulent mesoscale flow and substantial local thermodynamic variability. Recent work by \citet{Brooker+25} demonstrated systematic shortening of fuel ignition times near Rayleigh--Taylor unstable deflagration fronts, but the physical origin remained unclear. We investigate the thermodynamic evolution of fuel near the flame front using multidimensional simulations and Lagrangian tracer-particle analysis, focusing on flame-driven expansion and ignition-time variability in partially degenerate carbon--oxygen plasma. Tracer trajectories show that the most strongly preconditioned fuel parcels near the flame front, which form a minority of the fuel layer, undergo approximately pressure-constrained expansion with modest density reductions and temperature increases of $\approx 2\times10^{8}$~K to $\approx7\times10^{8}$~K ($\approx13$ to $63$ per cent above the unperturbed fuel temperature) between the low- and high-density models. Despite moderate thermodynamic perturbations, the strong temperature sensitivity of carbon ignition produces substantial shortening of ignition times. The results indicate a two-step mechanism: flame thermal expansion perturbs the fuel away from hydrostatic equilibrium, while restoration of pressure balance by weak acoustic waves redistributes internal energy from degenerate to thermal components. This raises the fuel temperature and produces localized thermodynamic preconditioning. These results suggest that unsteady thermonuclear flames can shorten ignition times ahead of the flame, influencing fuel over distances larger than the laminar flame thickness. Whether this preconditioning leads to secondary ignition or contributes to deflagration-to-detonation transition remains untested here, as nuclear burning is disabled in the analyzed fuel.
Comments33 pages, 14 figures, 2 appendices; submitted for publication in The Astrophysical Journal
