SIP-IFVM：日冕和日冕物质抛射的高效时间精确磁流体动力学模型
SIP-IFVM: Efficient time-accurate magnetohydrodynamic model of the corona and coronal mass ejections
AI总结：
本文提出了高效时间精确的三维单流体MHD日冕模型SIP-IFVM，通过伪时间推进方法和隐式算法加速CME模拟，在保证数值稳定性的同时能高效处理低等离子体β的时变事件。
摘要：
在本文中，我们提出了一种高效且时间精确的三维（3D）单流体 MHD 太阳日冕模型，并利用它来模拟 CME 的演化与传播。基于一个准稳态隐式 MHD 日冕模型，我们开发了一种高效的时间精确日冕模型，该模型可通过选择较大的时间步长来加速 CME 模拟。我们将其称为 Solar Interplanetary Phenomena-Implicit Finite Volume Method (SIP-IFVM) 日冕模型。我们实现了一种伪时间推进方法以提高时间精度。将一根轴线可设计成任意形状的正则化 Biot-Savart 定律（RBSL）磁通量绳插入背景日冕中，以触发 CME 事件。我们在 Carrington 自转（CR）2219 的背景日冕上进行了 CME 模拟，并评估了时间步长对模拟结果的影响。我们的研究表明，该模型能够在不到 0.5 小时内（使用 192 个 CPU 核心，约 1 M 个网格）模拟从太阳表面到 $20\; R_s$ 的 CME 演化与传播过程。与显式对应模型相比，该隐式日冕模型不仅速度更快，而且数值稳定性也有所提高。我们还进行了一项初始磁场被人为增强的特定模拟。结果表明，该模型能够有效处理随时间变化的低 $β$ 问题（$β<10^{-4}$）。此外，Orszag-Tang MHD 涡流模拟表明，该日冕模型中使用的伪时间推进方法能够模拟小尺度非稳态流动。模拟结果表明，该 MHD 日冕模型非常高效且数值稳定。它是一种及时且准确地模拟低等离子体 $β$ 太阳日冕中时变事件的有前景的方法。
英文摘要：
In this paper, we present an efficient and time-accurate three-dimensional (3D) single-fluid MHD solar coronal model and employ it to simulate CME evolution and propagation. Based on a quasi-steady-state implicit MHD coronal model, we developed an efficient time-accurate coronal model that can be used to speed up the CME simulation by selecting a large time-step size. We have called it the Solar Interplanetary Phenomena-Implicit Finite Volume Method (SIP-IFVM) coronal model. A pseudo-time marching method was implemented to improve temporal accuracy. A regularised Biot-Savart Laws (RBSL) flux rope, whose axis can be designed into an arbitrary shape, was inserted into the background corona to trigger the CME event. We performed a CME simulation on the background corona of Carrington rotation (CR) 2219 and evaluated the impact of time-step sizes on simulation results. Our study demonstrates that this model is able to simulate the CME evolution and propagation process from the solar surface to $20\; R_s$ in less than 0.5 hours (192 CPU cores, $\sim$ 1 M cells). Compared to the explicit counterpart, this implicit coronal model is not only faster, but it also has improved numerical stability. We also conducted an ad hoc simulation with initial magnetic fields artificially increased. It shows that this model can effectively deal with time-dependent low-$β$ problems ($β<10^{-4}$). Additionally, an Orszag-Tang MHD vortex flow simulation demonstrates that the pseudo-time-marching method used in this coronal model can simulate small-scale unsteady-state flows. The simulation results show that this MHD coronal model is very efficient and numerically stable. It is a promising approach to simulating time-varying events in the solar corona with low plasma $β$ in a timely and accurate manner.
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