发表机构
KU Leuven; University of Maria Curie-Skłodowska; University of Science and Technology of China（荷语鲁汶大学; 玛丽亚·居里-斯可罗多夫斯卡大学; 中国科学技术大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文通过提升COCONUT数值稳定性，实现高保真磁图直接驱动的日冕MHD模拟，发现其较传统滤波磁图模拟多产生约50%开放磁通，EUV图像更吻合观测，并揭示极区开放场在特定波段可呈亮结构，凸显极轨观测必要性。
AI 中文摘要
为了详细解析日冕结构，必须使用最小平滑处理的高保真磁图来约束日冕模型。本文提高了COCONUT的数值稳定性，使其能够直接由光球磁图（包括超过1000高斯（G）的磁场强度）驱动进行高效的日冕磁流体力学（MHD）模拟，并利用该模型研究通常从光球磁图中滤除的小尺度磁场结构对日冕模拟结果的影响。我们使用两种类型的磁图来约束该模型：一种是经过高斯平滑仅作少量预处理的高保真HMI光球磁图，其保留了高达1500 G的磁场强度；另一种是使用50阶滤波球谐函数处理的磁图，其磁场强度被限制在100 G以下。结果表明，COCONUT能够再现由pB和EUV观测揭示的大尺度日冕结构。与受传统滤波磁图约束的日冕MHD模拟相比，受高保真磁图约束的模拟产生的开放磁通（OMF）约多50%，并且生成的EUV图像与观测结果更为一致。此外，结果表明，在从低纬度观测的某些EUV波段（如193 Å通道）中，太阳极附近的开放场区域可能表现为通常与闭合场区域相关的亮结构。这一发现凸显了太阳极轨任务克服因从黄道面观测极区受限而产生的局限性和模糊性，并提供更完整的全太阳观测的必要性。
英文摘要
To resolve coronal structures in detail, it is essential to constrain the coronal model using high-fidelity magnetograms with minimal smoothing. In this paper, we improve the numerical stability of COCONUT to enable efficient coronal MHD simulations driven directly by photospheric magnetograms, including magnetic field strengths exceeding 1000 Gauss (G), and then use it to investigate the impact of small-scale magnetic field structures that are typically filtered out of photospheric magnetograms on the coronal simulation results. We constrain this model with two types of magnetograms: the high-fidelity HMI photospheric magnetogram with only minor preprocessing through Gaussian smoothing, which preserves magnetic field strengths reaching 1500 G, and one processed using 50th-order filtered spherical harmonics, where the magnetic field strength is limited to below 100 G. The results demonstrate that the COCONUT can reproduce the large-scale coronal structures revealed by pB and EUV observations. Compared with the coronal MHD simulation constrained by a conventionally filtered magnetogram, the simulation constrained by the high-fidelity magnetogram yields approximately $50\%$ more OMF and produces EUV images that are more consistent with the observations. Moreover, the results show that when viewed from low latitudes in certain EUV passbands, such as the 193~Å channel, open-field regions near the solar poles may appear as bright structures that are typically associated with closed-field regions. This finding highlights the need for solar polar-orbiting missions to overcome the limitations and ambiguities arising from the restricted view of the polar regions from the ecliptic plane and to provide more complete full-Sun observations.
Comments12 pages, 7 figures
