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武慧春教授研究成果入选浙江大学2016年度十大学术进展之一
2017-06-02
聚变理论与模拟中心
“浙江大学2016年度十大学术进展”评选活动于2016年1月11日正式启动，由各学部、科学技术研究院、校学术委员会委员以及同行专家等共推荐23项候选项目，最终评审结果于6月1日由浙江大学学术委员会正式发布：我中心武慧春教授的“球状闪电的相对论微波理论”入选“浙江大学2016年度十大学术进展”之一。入选公告链接：http://ac.zju.edu.cn/redir.php?catalog_id=455&object_id=13624入选成果简介：2016年6月，浙江大学聚变理论与模拟中心和物理系的武慧春教授发表了球状闪电的相对论微波理论[Wu, Sci. Rep. 2016]。该理论基于近十年观测到的闪电高能现象，认为闪电触及地面时产生了一个强流电子束；该电子束打击地面或穿透媒介时，产生了相对论微波；微波进而击穿空气，其辐射压排空产生的等离子体，形成了一个球形等离子体空泡。PIC数值模拟验证了整个物理过程。该理论能解释球闪的大多数特征：球闪大小(20-50cm)由电子束长度决定，实验观测显示后者可短至30cm；闪电高能电子能量约为10MeV，可穿透厚金属板，在出射面产生微波，这解释了密闭空间中的球闪形成；电子地面打击点和雷击点无关解释了球闪可远离闪电通道形成；还有其他许多特性的解释。闪电学术权威明确指出，不能解释球闪在密闭空间及远离雷击点形成的理论是不能接受的。武教授的理论是迄今可以解释这两点的唯一理论。该理论的一个推论是人们可能已经探测到与球闪同源的无线电波。武教授找到了该无线电信号，并利用上述球闪机理定量解释了其大多数特征[Wu, Geophys. Res. Lett. 2017]。该信号是美俄三颗卫星发现并研究了长达20多年的一种地球环境中最强的无线电波。该信号的存在和成功解释为球闪微波理论提供了一个强有力的实际依据。上述工作受邀参加了法国第一届闪电雷暴国际会议，报告得到了闪电科学家的高度评价和支持。美国斯蒂芬教授评价道：“The relativistic microwave theory of ball lightning recently proposed by Wu accounts for many of the leading characteristics of ball lightning, which most previous theories have failed to do.”报告图片被会议主页特写，并受邀加入第二届会议组委会。该工作还受邀在第一届亚太等离子体物理会议上做大会报告。迄今为止，球闪工作总浏览量超1.7万次，被英美西日等国媒体报道，20多个国家120多Twitter用户关注。全球关注度Altmetric指数超100，处在同期所有科技论文的前3%之列。被NatureAsia从Sci. Rep.在2016全年所发2万多篇论文中选出Highlight的五篇物理论文之一。美国新科学杂志Nautilus做了一个学术报道，提到：“Chinese scientist H.-C. Wu offered a compelling (令人信服) new explanation.”该工作还入选知社组织的“2016年中国新锐科技人物”。综上所述，武教授的球闪理论具有如下特点：①有闪电高能现象的实验基础；②是描述球闪形成的第一个自洽的定量理论，且有模拟支持；③成功解释了球闪的大多数特征，其中一部分是精确定量解释，另一部分是其他理论都不能解释而学术界要求必须解释的；④已得到国际同行的愈多认同；⑤其推论已得到验证。上述几点是其他球闪理论远远做不到的。
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等离子体中激光参量不稳定性放大的粒子模拟研究与分析
2017-05-10
聚变理论与模拟中心
题目：等离子体中激光参量不稳定性放大的粒子模拟研究与分析报告人：贾青博士，普林斯顿大学时间：1月12 日上午9:00-10:00 地点：中心会议室（教11 413-1）摘要：近年来，EW（10^18W）级短脉冲激光被提出用于研究核物理、真空非线性QED物理等领域。但由于压缩光栅热损伤阈值的限制，基于啁啾脉冲放大（CPA）构型的短脉冲激光装置的输出功率限制在数拍瓦（10^15W）水平。为实现高功率输出，研究人员提出利用没有激光损伤阈值的等离子体作为介质进行脉冲放大。本报告将简要介绍我们在等离子体中激光参量不稳定性放大领域开展的一些工作，主要包括：利用等离子体中不同参量不稳定进行的激光放大过程的区分和优劣比较，正负电子对等离子体中的参量放大分析，磁化等离子体中的参量放大的非线性分析及预聚焦脉冲的拉曼放大模拟等研究。
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陈骝教授获得2017年浙江省海外高层次人才联谊会“创新成果”奖
2017-05-10
聚变理论与模拟中心
陈骝教授获得2017年浙江省海外高层次人才联谊会“创新成果”奖1st Announcement of 1st Asia-Pacific Conference on Plasma Physics 1st Announcement on 1st Asia-Pacific Conference on Plasma Physics (AAPPS-DPP 2017) September 18-23, Golden Ox (Jinniu) Hotel Organized by AAPPS-DPP Hosted by Southwestern Institute of Physics Endorsed by CPS-DPP, CNS-NFPP, KPS-DPP, PSSI, JPS-DPP, JSPF Sponsored by Chengdu city and APCTP AAPPS-DPP executive committee (M. Kikuchi, chair) decided to organize the 1st Asia-Pacific Conference on Plasma Physics (AAPPS-DPP2017 in short). This conference will be the general plasma physics conference in Asia-Pacific region, similar to the APS-DPP and EPS-DPP conferences on plasma physics.
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托卡马克台基区的回旋动理学模拟
2017-04-24
聚变理论与模拟中心
title about: 托卡马克台基区的回旋动理学模拟speaker: 刘东剑Time: April 27th, 28th Venue: Rm. 413, Bld. 11#, Yuquan Campus
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Variational formulations of hybrid kinetic-MHD models by Alain J. Brizard
2017-04-17
聚变理论与模拟中心
Title about: Variational formulations of hybrid kinetic-MHD modelsSpeaker: Alain J. Brizard (Saint Michael’s College)Time: Friday, April 21st , 4:00 pm Venue: Rm. 413, Bld. 11#, Yuquan CampusAbstract ：Hybrid kinetic-MHD models (e.g., Chen-White-Rosenbluth model) play a crucial role in our ability to assess the impact of a distribution of energetic particles (e.g., runaway electrons or fusion products) on the stability of MHD modes in general magnetic geometry. The existence of a variational formulation ensures that the equations of the hybrid kinetic-MHD model are derived self-consistently and that important conservation laws involving the transfer of energy (or wave action) and momentum are accurately described.
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张双喜博士报告
2017-04-13
聚变理论与模拟中心
Title about: Modelling the Lagrangian of magnetized plasmas with electrostatic perturbations and low- frequency magnetic perturbations by gyrokinetic model Speaker: 张双喜 博士 Time: Tuesday, April 18th , 3:00 pm Venue: Rm. 413, Bld. 11#, Yuquan CampusAbstract ：It’s well-known that due to the fact that the inverse-square structure of Coulomb force determines Poisson’s equation which associates the electrostatic potential with the charge density on particle’s coordinates, the fundamental Lagrangian 1-form, which determines the dynamics of all ions and electrons in the magnetized plasma with electrostatic perturbations, can be modeled by a Vlasov-Poisson model. By transforming this Lagrangian 1-form to the new one on gyrocenter coordinates up to the second order, the new potential includes the potential generated by Coulomb force on the new coordinates plus a finite Larmor radius term. It’s shown that the fundamental Lagrangian 1-form on the new coordinates can still be modeled by a gyrokinetic Vlasov-Poisson model with the polarization density recovered on the new coordinates. The numerical application of this new model could help reduce numerical error, numerical instabilities and numerical burden for the simulation of the electrostatic turbulence in magnetized plasma. The similar method can also be applied to low-frequency magnetic perturbations resulting a gyrokinetic Ampere-Poisson model. Eventually, a gyrokinetic Ampere-Poisson-Vlasov model can be derived by combining electrostatic perturbations and low-frequency magnetic perturbations together.
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Six Lectures on Gyrokinetic Theory by Prof. Alain Brizard
2017-04-03
聚变理论与模拟中心
Title: Six Lectures on Gyrokinetic TheorySpeaker: Prof. Alain J. Brizard, Saint Michael’s College (USA)Time: April 10, April 12, April 14, April 17, April 19, April 21, 2017, 9:00-11:00 AMVenue: Rm. 413-1, Bld. 11#, Yuquan CampusYou are warmly welcomed to take part in it.
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Physics of Alfvén waves and energetic particles in fusion plasmas--Linear physics and stability in tokamaks by Prof. Fulvio Zonca
2017-04-03
聚变理论与模拟中心
Title: Physics of Alfvén waves and energetic particles in fusion plasmas--Linear physics and stability in tokamaksSpeaker: Prof. Fulvio ZoncaTime and Location: Lectures (9am-11am) and Q&A Sessions (3pm-5pm) will be held at IFTS on April 27-29 and May 4-6-8-10Venue: Rm. 413-1, Bld. 11#, Yuquan CampusYou are warmly welcomed to take part in it.
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任洋研究员报告
2017-04-03
聚变理论与模拟中心
title about: Exploring the Regime of Validity of Global Gyrokinetic Simulation with Spherical Tokamak Plasmasspeaker: Dr. Yang RenTime: Thursday, April 6th, 02:00 pmVenue: Rm. 413, Bld. 11#, Yuquan Campus题目：Exploring the Regime of Validity of Global Gyrokinetic Simulation with Spherical Tokamak PlasmasAbstract Plasma turbulence is considered one of the main mechanisms for driving anomalous thermal transport in magnetic confinement fusion devices. Based on first-principle model, gradient-driven gyrokinetic simulations have often been used to explain turbulence-driven transport in present fusion devices, and in fact, many present predictive codes are based on the assumption that turbulence is gradient-driven. However, using the electrostatic global particle-in-cell Gyrokinetic Tokamak Simulation (GTS) code [1], we will show that while global gradient-driven gyrokinetic simulations provide decent agreement in ion thermal transport with a set of NBI-heated NSTX H-mode plasmas, they are not able to explain observed electron thermal transport variation in a set of RF-heated L-mode plasmas, where a factor of 2 decrease in electron heat flux is observed after the cessation of RF heating. Thus, identifying the regime of validity of the gradient-driven assumption is essential for first-principle gyrokinetic simulation. This understanding will help us more confidently predict the confinement performance of ITER and future magnetic confinement devices. The work is supported by DOE and computational resource is provided by NERSC.[1] W.X. Wang et al., Phys. Plasmas 17, 072511 (2010)
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李罗权院士报告
2017-04-03
聚变理论与模拟中心
Title about: Generation of helium and oxygen EMIC waves by the bunch distribution of oxygen ions associated with fast magnetosonic shocks in the magnetosphere Speaker: 李罗权院士,Institute of Earth Science, Academia Sinica, Nankang, Taiwan Time: Thursday, April 6th, 3:30pmVenue: Rm. 413, Bld. 11#, Yuquan CampusAbstract: Electromagnetic ion cyclotron (EMIC) waves are often observed in the magnetosphere with frequency usually in the proton and helium cyclotron bands and sometimes in the oxygen band. The temperature anisotropy, caused by injection of energetic ions or by compression of magnetosphere, can efficiently generate proton EMIC waves, but not as efficient for helium or oxygen EMIC waves. Here we propose a new generation mechanism for helium and oxygen EMIC waves associated with fast magnetosonic shocks, which are observed in the magnetosphere. These shocks can be associated with either dynamic pressure enhancement or shocks in the solar wind and can lead to the formation of a “bunch” distribution in the perpendicular velocity plane of oxygen ions. The oxygen bunch distribution can excite strong helium EMIC waves and weak oxygen and proton waves. The dominant helium EMIC waves are strong in quasi-perpendicular propagation and show harmonics in frequency spectrum of Fourier analysis. The proposed mechanism can explain the generation and some observed properties of helium and oxygen EMIC waves in the magnetosphere.
