应物理学院何向磊邀请，中国科学技术大学张彦增研究员近日来我校进行学术报告，欢迎校内师生参加。
报告题目：Parallel electrostatic collisionless shocks in hot-cold ablative mixing plasmas
报告时间：2025年9月11日（星期四），上午9:30-11:00
报告地点：科学园C2栋413
报告摘要：Parallel electrostatic collisionless shocks are ubiquitous in space, astrophysical, and laboratory plasmas, and have been extensively studied through experiments, theory, and simulations since the 1960s. The most well-characterized scenarios resemble explosive expansions, where a high-pressure, high-density plasma expands into a low-density background. In such cases, the expanding (downstream) region typically has a uniform or elevated electron temperature and cold ions. In contrast, a frequently encountered yet less explored case involves a cold/dense plasma roughly in pressure balance with a hot/dilute plasma. Such a hot-cold interface is known to trigger a thermal collapse of the nearly collisionless hot background plasma (e.g. tokamak thermal quench), and an ablative mix of the cold ions with the background ions. Using first-principles kinetic simulations and theoretical analysis, we demonstrate the formation of a new type of electrostatic collisionless parallel shock in such hot–cold ablative mixing plasmas, even when the downstream plasma pressure is lower than that in the upstream. This shock is driven by heat flux from the hot plasma into the cold region, primarily via energetic tail electrons regulated by an ambipolar electric field, and it propagates into the ambient hot plasma. Shock-induced ion heating is remarkably efficient for a moderate electron temperature ratio via collisionless mixing of upstream hot ions and downstream cold ions, both of which have been converted into shock-front-bound flows accelerated by the ambipolar electric field that has a deep potential well anchored inside the shock front.
报告人简介：张彦增博士于 2020 年获加利福尼亚大学圣地亚哥分校博士学位，先后在美国洛斯阿拉莫斯国家实验室任主任博士后及二级科学家，并于 2025 年 7 月加入中国科学技术大学，任特任研究员。长期致力于磁约束聚变等离子体的理论解析与数值模拟研究，在托卡马克破裂、边界等离子体输运等方向取得了突出成果，主持和参与项目累计获资助逾千万美元。担任 Nature Communications、Scientific Reports、Physics of Plasmas 等多家国际期刊审稿人，在 Physical Review Letters、Nuclear Fusion、Physics of Plasmas 等等离子体物理领域权威期刊发表论文 30 余篇，其中第一作者论文 20 余篇；在国内外重要学术会议上作报告 20 余次。曾任国际知名会议 Sherwood 聚变理论会议执行委员会委员及副主席。
