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Pseudo-reconnection in MHD numerical simulation

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Chinese Science Bulletin 2000年第9期45卷 798-801页

作者： CHEN Pengfei FANG Cheng hu youqiu Department of Astronomy Nanjing UniversityNanjing 210093China Department of Space and Earth Sciences University of Science and Technology of ChinaHefei 230026China

A class of pseudo-reconnections caused by a shifted mesh in magnetohydrodynamics(MHD) simulations is reported. In terms of this mesh system, some non-physical results may be obtained in certain circumstances, e.g. mag... 详细信息

关键词： magnetohydrodynamics (MHD) numerical simulation magnetic reconnection.

Anisotropic propagation of flare-induced shocks

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Chinese Science Bulletin 1998年第5期43卷 402-404页

作者： hu youqiu University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230026, China Chinese Academy of Sciences University of Science and Technology of China Hefei China

It is demonstrated that the fastest propagation direction of a flare-induced shock deviates eastwards by about 4° at 1 AU relative to the flare normal if the shock introduced at 0.1 AU propagates along the local magnetic field, whereas it deviates westwards by about 1° if the introduced shock propagates in the radial direction instead.

关键词： solar flare MHD shock interplanetary dynamics.

Magnetohydrodynamics (MHD) numerical simulations on the interaction of the solar wind with the magnetosphere: A review

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Science China Earth Sciences 2013年第7期56卷 1141-1157页

作者： WANG Chi GUO XiaoCheng PENG Zhong TANG BinBin SUN TianRan LI WenYa hu youqiu State Key Laboratory of Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences School of Earth and Space Sciences University of Science and Technology of China

The magnetosphere is the outermost layer of the geospace, and the interaction of the solar wind with the magnetosphere is the key element of the space weather cause-and-effect chain process from the Sun to Earth, which is one of the most challenging scientific problems in the geospace weather study. The nonlinearity, multiple component, and time-dependent nature of the geospace make it very difficult to describe the physical process in geospace using traditional analytic analysis approach. Numerical simulations, a new research tool developed in recent decades, have a deep impact on the theory and application of the geospace. MHD simulations started at the end of the 1970s, and the initial study was limited to two-dimensional (2D) cases. Due to the intrinsic three-dimensional (3D) characteristics of the geospace, 3D MHD simulations emerged in the 1980s, in an attempt to model the large-scale structures and fundamental physical processes in the magnetosphere. They started to combine with the space exploration missions in the 1990s and make comparisons with observations. Physics-based space weather forecast models started to be developed in the 21st century. Currently only a few space-power countries such as USA and Japan have developed 3D magnetospheric MHD models. With the rapid advance of space science in China, we have developed a new global MHD model, namely PPMLR-MHD, which has high order spatial accuracy and low numerical dissipation. In this review, we will briefly introduce the global 3D MHD modeling, especially the PPMLR-MHD code, and summarize our recent work based on the PPMLR-MHD model, with an emphasis on the interaction of interplanetary shocks with the magnetosphere, large-scale current systems, reconnection voltage and transpolar potential drop, and Kelvin-Helmholtz (K-H) instability at the magnetopause.

关键词： solar wind magnetosphere MHD simulations

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部分开放多极磁场中的日冕磁绳灾变

空间科学学报 2005年第2期25卷 81-85页

作者：彭忠胡友秋中国科学技术大学地球与空间科学学院合肥230026

采用球坐标下二维三分量理想MHD模型,研究部分开放多极背景磁场中日冕磁绳的灾变现象.背景磁场由含3个闭合双极场的冕流和带赤道中性电流片的开放场构成,磁绳位于中心双极场的下方,其特性由环向磁通和轴向磁通表征.对给定的环向磁通,... 详细信息

采用球坐标下二维三分量理想MHD模型,研究部分开放多极背景磁场中日冕磁绳的灾变现象.背景磁场由含3个闭合双极场的冕流和带赤道中性电流片的开放场构成,磁绳位于中心双极场的下方,其特性由环向磁通和轴向磁通表征.对给定的环向磁通,存在轴向磁通的一个临界值;对给定的轴向磁通,也存在环向磁通的一个临界值.在该临界值以下,磁绳附着于太阳表面,系统处于平衡状态;该临界值一旦被超越,磁绳将脱离太阳表面向上喷发,说明部分开放多极背景磁场中的日冕磁绳系统存在灾变现象.本文算例表明,灾变点对应的磁能阈值超过对应部分开放场(中心双极场开放,两侧的双极场仍维持闭合)能量约15％,其超过部分可为日冕物质抛射一类太阳爆发提供能源.

关键词：磁流体力学灾变现象 MHD数值模拟开放多极磁场

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无力磁场的稳定性

天体物理学报 1991年第1期11卷 58-65页

作者：胡友秋中国科学技术大学地球和空间科学系

无力场被广泛用来模拟太阳活动区的强磁场,本文从Bernstein能量原理出发,导出了无力场能量原理的普遍形式,并给出了若干稳定性的充分条件,它们可方便而有效地对无力场进行稳定性判断。

关键词：无力场磁场稳定性太阳磁流体

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磁通量消失所形成的中性电流片

Chinese Journal of Astronomy and Astrophysics 1984年第1期 14-24页

作者：胡友秋中国科学技术大学地球和空间科学系

在与太阳耀斑有关的活动区中,一般呈现各种复杂多变的磁场结构,其中特别是光球层表面局部地区磁通量的出现和消失.在无限电导率的假定下,上述两种现象都会在日冕中产生中性电流片;通常人们认为这正是耀斑前一种可能的贮能机制.Tur和Pri... 详细信息

在与太阳耀斑有关的活动区中,一般呈现各种复杂多变的磁场结构,其中特别是光球层表面局部地区磁通量的出现和消失.在无限电导率的假定下,上述两种现象都会在日冕中产生中性电流片;通常人们认为这正是耀斑前一种可能的贮能机制.Tur和Priest通过两个特例讨论了新磁通量的出现所形成的电流片的特征,这两个例子的背景磁场分别取为双极场和均匀场.本文采用同样的背景场,讨论磁通量消失所形成的电流片,并指出和纠正文[2]对第二个例子的分析中的一些原则错误.

关键词：电流片几何形式自由能电流分布热力学势热力学性质磁场冻结磁通量太阳耀斑偶极子场磁场位形末态日冕太阳大气

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磁通量喷发的大气响应Ⅱ.太阳附近的慢激波

天体物理学报 1991年第2期11卷 188-193页

作者：胡友秋郑惠南中国科学技术大学地球和空间科学系

日冕物质喷射的观测速度常低于阿尔芬波速的估计值而高于背景日冕声速,这说明日冕物质喷射可能在日冕中形成慢激波。本文取带赤道电流片的冕流结构作为背景,用冕流底部的磁通量喷发作为驱动机制,对日冕物质喷射触发的慢激波进行数值模... 详细信息

日冕物质喷射的观测速度常低于阿尔芬波速的估计值而高于背景日冕声速,这说明日冕物质喷射可能在日冕中形成慢激波。本文取带赤道电流片的冕流结构作为背景,用冕流底部的磁通量喷发作为驱动机制,对日冕物质喷射触发的慢激波进行数值模拟。结果表明,电流片对激波结构有着重要影响。慢激波只出现在电流片的外部,在电流片中逐渐过渡为快激波,慢激波前方的背景磁场在快磁声波的作用下显著偏转,背景密度下降超过10％。慢激波的纬度范围有限,从电流片的外沿大约延伸到±20°,且具有凹向上方的外形。

关键词：太阳磁场慢激波

磁通量喷发的大气响应——Ⅲ.太阳附近激波的演化

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天体物理学报 1992年第1期12卷 54-62页

作者：胡友秋王赤郑惠南中国科学技术大学地球和空间科学系合肥230026

作为本系列的最后一篇,本文研究日冕大气中的激波演化.结果表明,日冕背景大气和磁场的非均匀性对激波结构和演化起着决定作用。太阳附近形成的慢激波-快磁声波系统,将在向外传播的过程中演变为以中间激波作为必要组成部分的混合激波。... 详细信息

作为本系列的最后一篇,本文研究日冕大气中的激波演化.结果表明,日冕背景大气和磁场的非均匀性对激波结构和演化起着决定作用。太阳附近形成的慢激波-快磁声波系统,将在向外传播的过程中演变为以中间激波作为必要组成部分的混合激波。该混合激波在沿电流片传播时能继续维持,而在沿单极开放磁场传播时则进一步演变为纯快激波。

关键词：太阳磁场混合激波磁通量喷发

Photo‑Energized MoS_(2)/CNT Cathode for High‑Performance Li–CO_(2)Batteries in a Wide‑Temperature Range

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Nano-Micro Letters 2025年第1期17卷 160-175页

作者： Tingsong hu Wenyi Lian Kang hu Qiuju Li Xueliang Cui Tengyu Yao Laifa Shen Jiangsu Key Laboratory of Materials and Technologies for Energy Storage College of Materials Science and TechnologyNanjing University of Aeronautics and AstronauticsNanjing 210016People’s Republic of China

Li–CO_(2) batteries are considered promising energy storage systems in extreme environments such as Mars;however,severe performance degradation will occur at a subzero temperature owning to the sluggish reaction ***,a photo-energized strategy adopting sustainable solar energy in wide working temperature range Li–CO_(2) battery was achieved with a binder-free MoS_(2)/carbon nanotube(CNT)photo-electrode as *** unique layered structure and excellent photoelectric properties of MoS_(2) facilitate the abundant generation and rapid transfer of photo-excited carriers,which accelerate the CO_(2) reduction and Li_(2)CO_(3) decomposition upon *** illuminated battery at room temperature exhibited high discharge voltage of 2.95 V and mitigated charge voltage of 3.27 V,attaining superior energy efficiency of 90.2%and excellent cycling stability of over 120 *** at an extremely low temperature of−30℃,the battery with same electrolyte can still deliver a small polarization of 0.45 V by the photoelectric and photothermal synergistic mechanism of MoS_(2)/CNT *** work demonstrates the promising potential of the photo-energized wide working temperature range Li–CO_(2) battery in addressing the obstacle of charge overpotential and energy efficiency.

关键词： Li-CO_(2)batteries Photo-energized Wide operation-temperature Kinetics MoS_(2)