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Characteristics of the boundary layer of magnetic clouds and a new definition of the cloud boundary

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Science China(Technological Sciences) 2003年第1期46卷 19-32页

作者：魏奉思刘睿范全林冯学尚 sigma Weather Group Laboratory for Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing 100080 China

Based on the analysis of the boundaries of 70 magnetic clouds from 1967 to 1998, and relatively complete spacercraft observations, it is indicated that the magnetic cloud boundaries are boundary layers formed through the interaction between the magnetic clouds and the ambient medium. Most of the outer boundaries of the layers, with relatively high proton temperature, density and plasma β, are magnetic reconnection boundaries, while the inner boundaries, with low proton temperature, proton density and plasma β, separate the main body of magnetic clouds, which has not been affected by the interaction, from the boundary layers. The average time scale of the front boundary layer is 1.7 h and that of the tail boundary layer 3.1 h. It is also found that the magnetic probability distribution function undergoes significant changes across the boundary layers. This new definition, supported by the preliminary numerical simulation in principle, could qualitatively explain the observations of interplanetary magnetic clouds, and could help resolve the controversy in identifying the boundaries of magnetic clouds. Our concept of the boundary layer may provide some understanding of what underlies the observations, and a fresh train of thought in the interplanetary dynamics research.

关键词： interplanetary, magnetic cloud boundary, magnetic reconnection.

Spatial Distribution and Anisotropy of Energetic Particles Accelerated by Shock Waves: Focused Transport Model

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Chinese Physics Letters 2013年第1期30卷 235-238页

作者： ZUO Ping-Bing FENG Xue-Shang sigma Weather Group State Key Laboratory of Space WeatherCenter for Space Science and Applied ResearchChinese Academy of SciencesBeijing 100190

The focused transport equation(FTE)contains the necessary physics of shock acceleration but avoids the limitation of small pitch-angle anisotropy inherent in the cosmic ray transport *** present a focused transport model based on FTE to investigate the spatial distribution and anisotropy of energetic particles accelerated by shock waves from pickup *** is found that in the upstream of the shock,the accelerated particles are highly anisotropic,but in the downstream it is approximately *** intensity spike is formed across the *** simulation results are qualitatively consistent with the observations of the termination shock particles by two Voyager spacecraft in the vicinity of the termination shock.

关键词： equation. shock anisotropy

Numerical study of successive CMEs during November 4―5, 1998

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Science China(Technological Sciences) 2008年第10期51卷 1600-1610页

作者： ZHOU YuFen & FENG XueShang sigma Weather Group, State Key Laboratory for Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190, China sigma Weather Group State Key Laboratory for Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing China

We present the solar-terrestrial transit process of three successive coronal mass ejections (CMEs) of November 4―5, 1998 originating from active region 8375 by using a time-dependent three-dimensional magnetohydrodynamics (MHD) simula-tion. These CMEs interacted with each other while they were propagating in inter-planetary space and finally formed a "complex ejecta". A newly developed SIP-CESE MHD model was applied to solve MHD equations numerically. The quiet solar wind was started from Parker-like 1D solar wind solution and the magnetic field map was calculated from the solar photospheric magnetic field data. In our simulation, the ejections were initiated using pulse in the real active region 8375. The interplanetary disturbance parameters, such as speed, direction and angular size of the expanding CME, were determined from the SOHO/LASCO data with the cone-model. We discussed the three-dimensional aspects of the propagation, in-teraction and merging of the three ejections. The simulated interplanetary shocks were compared with the nearby-Earth measurement. The results showed that our simulation could reproduce and explain some of the general features observed by satellite for the "complex ejecta".

关键词： complex ejecta three-dimensional MHD simulation SIP-CESE MHD model

Testing a solar coronal magnetic field extrapolation code with the Titov–Dmoulin magnetic flux rope model

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Research in Astronomy and Astrophysics 2016年第1期16卷 129-134页

作者： Chao-Wei Jiang Xue-Shang Feng sigma Weather Group State Key Laboratory for Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing 100190 China

In the solar corona, the magnetic flux rope is believed to be a fundamental structure that accounts for magnetic free energy storage and solar eruptions. Up to the present, the extrapolation of the magnetic field from boundary data has been the primary way to obtain fully three-dimensional magnetic information about the corona. As a result, the ability to reliably recover the coronal magnetic flux rope is important for coronal field extrapolation. In this paper, our coronal field extrapolation code is examined with an analytical magnetic flux rope model proposed by Titov ＆ D6moulin, which consists of a bipolar magnetic configuration holding a semi-circular line-tied flux rope in force-free equilibrium. By only using the vector field at the bottom boundary as input, we test our code with the model in a representative range of parameter space and find that the model field can be reconstructed with high accuracy. In particular, the magnetic topological interfaces formed between the flux rope and the surrounding arcade, i.e., the ＂hyperbolic flux tube＂ and ＂bald patch separatrix surface,＂ are also reliably reproduced. By this test, we demonstrate that our CESE-MHD-NLFFF code can be applied to recovering the magnetic flux rope in the solar corona as long as the vector magnetogram satisfies the force-free constraints.

关键词： magnetic fields -- magnetohydrodynamics (MHD) -- methods: numerical -- Sun: corona

Clear cell hepatocellular carcinoma: origin,metabolic traits and fate of glycogenotic clear and ground glass cells

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Hepatobiliary & Pancreatic Diseases International 2017年第6期16卷 570-594页

作者： Peter Bannasch Silvia Ribback Qin Su Doris Mayer German Cancer Research Center HeidelbergGermany Institut fur Pathologie Universitatsmedizin Greifswald Greifswald Germany Cell Marque Millipore-Sigma Rocklin USA

Clear cell hepatocellular carcinoma(CCHCC)has hitherto been considered an uncommon, highly differentiated variant of hepatocellular carcinoma(HCC) with a relatively favorable prognosis. CCHCC is composed of mixtures of clear and/or acidophilic ground glass hepatocytes with excessive glycogen and/or fat and shares histology, clinical features and etiology with common HCCs. Studies in animal models of chemical, hormonal and viral hepatocarcinogenesis and observations in patients with chronic liver diseases prone to develop HCC have shown that the majority of HCCs are preceded by, or associated with, focal or diffuse excessive storage of glycogen(glycogenosis) which later may be replaced by fat(lipidosis/steatosis). In ground glass cells, the glycogenosis is accompanied by proliferation of the smooth endoplasmic reticulum, which is closely related to glycogen particles and frequently harbors the hepatitis B surface antigen(HBs Ag).From the findings in animal models a sequence of changes has been established, commencing with preneoplastic glycogenotic liver lesions, often containing ground glass cells, and progressing to glycogen-poor neoplasms via various intermediate stages, including glycogenotic/lipidotic clear cell foci, clear cell hepatocellular adenomas(CCHCA) rich in glycogen and/or fat, and CCHCC. A similar process seems to take place in humans, with clear cells frequently persisting in CCHCC and steatohepatitic HCC, which presumably represent intermediate stages in the development rather than particular variants of HCC. During the progression of the preneoplastic lesions,the clear and ground glass cells transform into cells characteristic of common HCC. The sequential cellular changes are associated with metabolic aberrations, which start with an activation of the insulin signaling cascade resulting in preneoplastic hepatic glycogenosis. The molecular and metabolic changes underlying the glycogenosis/lipidosis are apparently responsible for the dramatic metabo

关键词： clear cell hepatocellular carcinoma phenotypic heterogeneity glycogenosis lipidosis preneoplastic glycogenosis progression metabolic aberrations

Recent progress in MHD simulations of the solar-terrestrial connection

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Science China(Technological Sciences) 2015年第12期58卷 2212-2213页

作者： FENG XueShang ZUO PingBing sigma Weather Group State Key Laboratory of Space Weather National Space Science CenterChinese Academy of Sciences

In recent years,considerable efforts on Magnetohydrodynamic(MHD)simulation have been made to better understand the solar-terrestrial connection,*** propagation and evolution of solar wind and solar storm as well as their effects on terrestrial *** paper briefly reviews these works based on the selected publications during 2013–2014 that cover the solar and solar wind model,solar windMoon interaction model,solar wind-magnetosphere coupling model,and magnetospheric model,etc.

关键词： MHD数值模拟太阳风暴地球系统连线磁流体动力学交互模型耦合模型太阳能

An asynchronous and parallel time-marching method: Application to three-dimensional MHD simulation of solar wind

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Science China(Technological Sciences) 2009年第10期52卷 2895-2902页

作者： SHEN Fang FENG XueShang SONG WenBin sigma Weather Group State Key Laboratory for Space WeatherCenter for Space Science and Applied ResearchChinese Academy of SciencesBeijing 100190China

An asynchronous and parallel time-marching method for three-dimensional (3D) time-dependent magnetohydrodynamic (MHD) simulation is used for large-scale solar wind simulation. It uses different local time steps in the corona and the heliosphere according to the local Courant-Friedrichs-Levy (CFL) conditions. The solar wind background with observed solar photospheric magnetic field as input is first presented. The simulation time for the background solar wind by using the asynchronous method is <1/6 of that by using the normal synchronous time-marching method with the same computation precision. Then, we choose the coronal mass ejection (CME) event of 13 November, 2003 as a test case. The time-dependent variations of the pressure and the velocity configured from a CME model at the inner boundary are applied to generate transient structures in order to study the dynamical interaction of a CME with the background solar wind flow between 1 and 230 Rs. This time-marching method is very effective in terms of computation time for large-scale 3D time-dependent numerical MHD problem. In this validation study, we find that this 3D MHD model, with the asynchronous and parallel time-marching method, provides a relatively satisfactory comparison with the ACE spacecraft obser- vations at L1 point.

关键词： asynchronous parallel MHD simulation CME

The heating of the solar transition region

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Research in Astronomy and Astrophysics 2010年第6期10卷 529-532页

作者： Wen-Bin Song Xue-Shang Feng Fang Shen sigma Weather Group State Key Laboratory of Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing 100190 China

The temperature curve in the solar chromosphere has puzzled astronomers for a long time. Referring to the structure of supergranular cells, we propose an inductive heating model. It mainly includes the following three steps. （1） A small-scale dynamo exists in the supergranulation and produces alternating small-scale magnetic fluxes; （2） The supergranular flow distributes these small-scale fluxes according to a regular pattern; （3） A skin effect occurs in the alternating and regularly-distributed magnetic fields. The induced current is concentrated near the transition region and heats it by resistive dissipation.

关键词： Sun transition region -- Sun granulation

NGD Analysis of Defected Ground and SIW-Matched Structure

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Chinese Journal of Electronics 2023年第2期32卷 343-352页

作者： GU Taochen WAN Fayu GE Junxiang Lalléchère Sébastien Rahajandraibe Wenceslas Ravelo Blaise Nanjing University of Information Science & Technology (NUIST) Université Clermont Auvergne (UCA) CNRS SIGMA Clermont Aix-Marseille University CNRS University of Toulon

A bandpass negative group delay(NGD)passive circuit based on defect ground structure(DGS)and substrate integrated waveguide(SIW)-matched is developed in the paper. The NGD DGS topology is originally built with notched cells associated with self-matched substrate waveguide elements. The DGS design method is introduced as a function of the geometrical notched and SIW via elements. Then, parametric analyses based on full wave 3-D electromagnetic S-parameter simulations were considered to investigate the influence of DGS physical size effects. The design method feasibility study is validated with fully distributed microstrip circuit prototype. Significant bandpass NGD function performances were validated with 3-D simulations and measurements with-1.69 ns negative group delay value around 2 GHz center frequency over 33.7 MHz NGD bandwidth. Insertion loss is 4.37 d B, and reflection loss reaches 41.5 d B.

关键词： Solid modeling Prototypes Electromagnetic waveguides Reflection Passive circuits Delays Frequency measurement