Analytical Model of Foreshock Ion Interaction With a Discontinuity: A Statistical Study
Analytical Model of Foreshock Ion Interaction With a Discontinuity: A Statistical Study
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DOI：
10.1029/2022ja031162
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发表时间：
2023-04
期刊：
影响因子：
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通讯作者：
T. Liu;A. Vu;V. Angelopoulos;Hui Zhang
中科院分区：
文献类型：
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作者：
T. Liu;A. Vu;V. Angelopoulos;Hui Zhang
当太阳风间断与前震离子相互作用时，可以形成前震瞬变，如热流异常和前震气泡。这些产生了显著的动态压力扰动，干扰了弓形激波、磁层顶和磁层-电离层系统。然而，目前这些现象是不可预测的。本文导出了前震离子绕不连续面偏旋的解析方程和由此产生的电流密度。在这项研究中，我们利用推导出的电流密度强度来模拟能量转换的前震离子，驱动向外运动或膨胀的太阳风等离子体远离不连续性。我们表明，模型扩展速度匹配不同前震离子参数的本地混合模拟。使用MMS，我们进行了统计研究表明，该模型的膨胀速度与磁场强度的变化是适度相关的，并与相关系数大于0.5的不连续性周围的动压降低。我们使用ARTEMIS和MMS之间的连接来表明，对于那些已经形成的前震瞬变，模型扩展速度通常很大。我们的研究结果表明，我们的模型可以合理地成功预测由前震离子不连续相互作用引起的显着动态压力扰动。我们讨论了未来改进模型的方法。
When a solar wind discontinuity interacts with foreshock ions, foreshock transients such as hot flow anomalies and foreshock bubbles can form. These create significant dynamic pressure perturbations disturbing the bow shock, magnetopause, and magnetosphere‐ionosphere system. However, presently these phenomena are not predictable. In the accompanying paper, we derived analytical equations of foreshock ion partial gyration around a discontinuity and the resultant current density. In this study, we utilize the derived current density strength to model the energy conversion from the foreshock ions, which drives the outward motion or expansion of the solar wind plasma away from the discontinuity. We show that the model expansion speeds match those from local hybrid simulations for varying foreshock ion parameters. Using MMS, we conduct a statistical study showing that the model expansion speeds are moderately correlated with the magnetic field strength variations and the dynamic pressure decreases around discontinuities with correlation coefficients larger than 0.5. We use conjunctions between ARTEMIS and MMS to show that the model expansion speeds are typically large for those already‐formed foreshock transients. Our results show that our model can be reasonably successful in predicting significant dynamic pressure disturbances caused by foreshock ion‐discontinuity interactions. We discuss ways to improve the model in the future.