【学术报告】 ～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～ 报告题目： The MHD-PIC method: applications and extension 报告人： 白雪宁博士 报告人单位：清华大学 报告语言： 中文 报告时间： 2023年6月5日(星期一)上午10:00 - 11:00 报告地点： 1号楼502会议室 报告摘要： ～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～ I will first give an overview of the MHD-PIC method, which is developed to study the kinetic physics of cosmic-ray (CR) particles interacting with a background thermal plasma. It treats the background plasma as a fluid described by MHD, while treats the cosmic-rays as particles using the conventional PIC approach, with backreaction to conserve momentum and energy. It greatly alleviates the issue of scale separation encountered in conventional PIC approach for CR-related problems, such as particle acceleration in shocks. We have recently implemented this method to the Athena++ MHD code, with mesh refinement capabilities to further boost the accessible scale hierarchy. As one major application, I will describe our simulations of the CR gyro-resonant instabilities, being the key microphysical mechanism behind CR feedback that involves substantial scale separation. Our simulations enable first-principle characterization of the CR transport coefficients, which can be eventually incorporated into subgrid prescriptions of CR feedback. Finally, I will describe the extension of the method to MHD-gPIC, where particles are integrated under the guiding center approximation with drift motion, with the potential to study particle acceleration in magnetic reconnection. ～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～～ 个人简介： Bio: Prof. Xuening Bai graduated from Tsinghua University with a B.S. in mathematics and physics in 2007, and obtained his PhD in astrophysics from Princeton University in 2012. He was a Hubble Fellow and Institute for Theory and Computation (ITC) fellow at the Harvard-Smithsonian Center for Astrophysics from 2012-2017. He joined the faculty at the Institute for Advanced Study, Tsinghua University in 2017, and is jointly affiliated with Department of Astronomy. He is a theoretical and computational astrophysicist. His research group studies protoplanetary disks and planet formation, as well as several aspects of plasma astrophysics especially on cosmic-ray acceleration and transport, and develops computational tools for related applications. 本通知也可以在云台学术报告网页看到： http://www.ynao.cas.cn/xwzx/xstg/ 申请安排学术报告的同事请参见台学术报告管理办法： http://www.ynao.cas.cn/xwzx/xstg/gzzd/ 云台邀请团组：太阳活动与CME理论研究团组、云南天文台青促会小组 邀请方联系人：林隽，13116242627;倪蕾18987287091 5月24日
