RIKEN介观器件腔中粒子输运过程的混沌性质及分形自相似结构研究

研究了粒子在RIKEN介观器件中的输运性质, RIKEN器件的理论模型是二维Sinai台球的一种, 是研究粒子逃逸曲线混沌性质和分形规律的理想模型之一. 采用逃逸曲线定性比较和分形维数定量计算两种方法, 得到了开口宽度、腔长、拐角位置、圆弧半径等器件参数对逃逸曲线混沌区域分布的影响规律. 结果发现逃逸曲线中存在分形自相似结构, 揭示了粒子在RIKEN介观器件腔中输运过程存在的混沌性质, 并首次运用"眼式结构"分析和相似比比较等方法对分形自相似结构进行了验证. 关键词： 介观器件 混沌性质 分形自相似 分形维数     

北半球环流系统季节内及年际以上振荡信号的信息传输

利用NCEP/NCAR月平均高度场再分析资料,分别提取季节内和年际以上振荡的基本特征和形式,运用信息传输理论分析这两种振荡信号的信息在低纬度与中高纬度间的传输.发现季节内振荡信号信息损失率较年际以上的偏大,且在特定地区这两种振荡信号的信息具有反向传输的特征;空间传输的水平分布上,两种振荡信号均表现为纬向上低纬度信息损失率大且海陆分布差异显著;空间传输的垂直分布上,年际以上振荡信号的低纬度高空信息损失率较大,中高纬度从对流层至平流层底信息损失率都较小,而季节内振荡信号则是低空信息损失率大,高空信息损失率小. 关键词： 滤波 高度场 信息损失率     

太阳活动与地球的空间环境

 光辉的太阳是地球万物生长的天然能量源泉,它不断地向太空发射大量的光和热．观测表明,太阳光球及其以上的太阳较外层大气中,时常有较大尺度或局部区域的、缓慢的或爆发型的变化现象,诸如太阳黑子、日珥和耀斑等,太阳物理学家把这些现象统称为“太阳活动”．太阳活动现象非常复杂多变,可以说是相当的丰富多彩．太阳黑子数目的变化具有显著的周期性,太阳黑子大量出现的期间叫做太阳活动峰年,黑子极少的期间称为太阳活动谷年或低年,两个峰年之间的周期平均约１１年．随着２１世纪的来临,美国国家海洋和大气管理局的科学家发出警告说,２０００年太阳活动将进人极大年──即太阳活动高峰期,剧烈的太阳活动可能会扰乱近地空间环境.     

太阳活动第22周峰年和峰年联合观测

 众所周知,太阳的活动有着为期11年的周期性变化,目前太阳正处在第22活动周的峰年期间.那末,什么是太阳活动峰年?为什么要研究峰年太阳活动,这是当前人们颇为关心的话题.一、太阳活动周期太阳活动周期,也称为太阳黑子活动周期,它是根据日面黑子数的变化规律而确定的.1848年,德国天文学家沃尔夫提出了一种太阳黑子的计数方法:R=K(N+10g),式中g为日面上出现的黑子群的群数,N是日面上单个黑子的总数,K则是一种改正数.与观测时的仪器、方法、条件和观测人员的个人因素等有关.R称为黑子相对数或沃尔夫数,由于其简便有效,一直沿用至今,成为序列最长、最重要的一种太阳活动指数.     

二维logistic映射的动力学行为和奇怪吸引子的分形特征

研究了二维logistic映射的动力学行为和奇怪吸引子的分形特征.利用分岔图、相图和Lyapunov指数谱分析系统的分岔过程,研究系统通向混沌的道路并确定系统处于混沌运动的参数区间;采用G-P算法计算奇怪吸引子的关联维数和Kolmogorov熵,对奇怪吸引子的分形特征定量刻画;采用逃逸时间算法构造奇怪吸引子的彩色广义M-J集,对奇怪吸引子的分形特征定性表征.结果表明,这些分析方法的配合使用可以更全面、形象地描述奇怪吸引子的分形特征.     

输油管道压力时间序列混沌特性研究

输油管道压力波动的内在动态特征,采用非线性的分析方法探讨了实测输油管道压力波动中存在混沌动态特性的可能性. 以6个典型的输油管道压力实测数据集为研究对象,重构相空间、求得了分形维数和Lyapunov指数谱、验证了数据的平稳性和非线性. 通过对所得结果的分析,从理论上证明了输油管道压力信号具有严格混沌动态特性. 为基于输油管道压力时间序列的研究提供了混沌理论基础. 关键词： 压力时间序列 Lyapunov指数 分形维数 混沌     

二维Hénon-Heiles势及其变形势体系逃逸率与分形维数的研究

采用Chin和Chen的动力学算法追踪粒子在体系中的运动情况, 首次研究并对比了粒子在Hénon-Heiles体系与变形Hénon-Heiles六边形体系中的混沌逃逸规律, 在Hénon-Heiles体系中, 对于不同能量范围, 分形维数与逃逸率随能量而改变, 但在变形Hénon-Heiles六边形体系中, 仅在低能区分形维数与逃逸率随能量的改变而变化, 而高能区逃逸率和分形维数趋于稳定值. 并且得到普遍规律, 即不同混沌体系中粒子的混沌逃逸率和粒子逃逸的分形维数呈现较强的线性相关性. 因而分形维数可以作为工具研究混沌体系中粒子的逃逸规律, 在介观器件设计中可以通过研究混沌电子器件的分形维数来表征粒子在器件中的传输行为.     

海杂波背景下的目标检测新方法

提出了一种基于分形布朗运动模型的S波段雷达海杂波分形维数提取方法.分析了基于记忆库混沌时间序列预测方法，引入一种改进核函数的支持向量机分类器.在此基础上，提出了一种新的海杂波背景下目标检测方法.应用S波段雷达实测海杂波数据，计算得到了该信号的分形维数与Lyapunov指数，验证了S波段雷达海杂波的混沌分形特性.仿真实验结果验证了该方法具有较强的检测能力和抗杂波性能. 关键词： 分形布朗运动 分形维数 记忆库预测方法 支持向量机分类器     

不平静的太阳

太阳是地球上光和热的源泉、对于人类来说,光辉的太阳无疑是宇宙中最重要的恒星.在古代,太阳一直是人们顶礼膜拜的对象、早在几千年前,中国甲骨文或一些古籍上就有对日食和太阳黑子现象的记载.1609年,伽利略率先用天文望远镜观测太阳黑子,1666年牛顿用棱镜发现了太阳可见光光谱。19世纪以来,随着观测的全面深入,科学家们发现了许多太阳活动现象,以及太阳活动与地球气候的变迁以及日地空间物理现象有着密切的关系、20世纪中,进入空间时代以来,科学家们利用一切手段,开始全波段观测太阳,并深入研究太阳活动及其对地球的影响.     

浅谈分形

 复杂的生命现象,暄闹的都市生活,蜿蜒曲折的海岸线,坑坑洼洼的地面等等,都表现出了客观世界极为丰富的现象。但基于古典的欧几里得几何学的各门自然科学总是把研究对象想象成一个个规则的形体,而我们生活的世界实际上却是不规则和支离破碎的,与欧几里得几何图形相比,拥有完全不同层次的复杂性。分形几何则提供了一种描述这种不规则复杂现象中的秩序和结构的新方法。通俗地说,分形几何就是研究无限复杂但具有一定意义下的自相似图形和结构的几何学。     

Predicting solar cycle 24 with a solar dynamo model

Whether or not the upcoming cycle 24 of solar activity will be strong is being hotly debated. The solar cycle is produced by a complex dynamo mechanism. We model the last few solar cycles by "feeding" observational data of the Sun's polar magnetic field into our solar dynamo model. Our results fit the observed sunspot numbers of cycles 21-23 reasonably well and predict that cycle 24 will be about 35% weaker than cycle 23.     

Millennium-scale sunspot number reconstruction: evidence for an unusually active sun since the 1940s

The extension of the sunspot number series backward in time is of considerable interest for dynamo theory, solar, stellar, and climate research. We have used records of the (10)Be concentration in polar ice to reconstruct the average sunspot activity level for the period between the year 850 to the present. Our method uses physical models for processes connecting the (10)Be concentration with the sunspot number. The reconstruction shows reliably that the period of high solar activity during the last 60 years is unique throughout the past 1150 years. This nearly triples the time interval for which such a statement could be made previously.     

Phase asynchrony between flare index and sunspot activity

In this paper,the relative phase relationship between flare index and sunspot activity(sunspot numbers and sunspot areas) is investigated.It is found that(i) the flare index and sunspot activity are asynchronous in phase space at all period scales,and the former lags behind the latter,which implies our results are supported for the integral response model;(ii) their diferent definitions and physical meanings may be a major reason for their phase asynchrony between them,and the solar flare activity favor to be related to the magnetic complex rather than magnetic strength.     

On the new prolonged solar activity minimum

The current 24th solar activity cycle started in 2008 and continuing to the present is anomalous in comparison with previous cycles. Its unusual properties include a low sunspot number R _z for a long time, a weak interplanetary magnetic field, a weak polar photospheric field in the Sun, and others. Beginning in 1000 to the present, five prolonged solar activity minima took place. These minima occurred in time intervals, when the distance between the center of mass of the solar system and the Sun center changed several times from maximum to minimum values for 40–70 years. Since the beginning of the new millennium, exactly such a period started and it can be assumed that we entered a new prolonged minimum which will last for several decades. In the current 24th and subsequent 2–3 solar activity cycles, annual average sunspot numbers will be low, R _zmax ≤ (50–70).     

Investigation of the helicity of magnetic fields on the Sun within the Parker dynamo model

Construction of the butterfly diagrams for the magnetic helicity in several approximations of a Parker dynamo has been carried out. The diagrams are constructed both for the cases of efficient generation of the magnetic field (large dynamo numbers) and for the weak generation (a small dynamo number). The corresponding asymptotic solution to the solar dynamo is used in the first case. The butterfly diagrams for different values of the meridional circulation were studied due to this solution. The butterfly diagrams are constructed and based on the few-mode approximation, which is valid for moderate dynamo numbers. The issue of which butterfly diagram features are common in all these approximations and can be compared with observational data is discussed.     

Magnetic field propagation in a stellar dynamo

Numerical simulations of stellar dynamos are reviewed. Dynamic dynamo models solve the nonlinear, three-dimensional, time-dependent, magnetohydrodynamic equations for the convective velocity, the thermodynamic variables, and the generated magnetic field in a rotating, spherical shell of ionized gas. When the dynamo operates in the convection zone, the simulated magnetic fields propagate away from the equator in the opposite direction inferred from the solar butterfly diagram. When simulated at the base of the convection zone, the fields propagate in the right direction at roughly the right speed. However, owing to the numerical difficulty, a full magnetic cycle has not been simulated in this region. As a result, it is still uncertain where and how the solar dynamo operates.     

基于混沌理论的太阳黑子数平滑月均值预报

太阳黑子活动长期预报对航天、通讯、防灾等具有重要的指导意义. 针对加权一阶局域法在多步预测时存在累积误差效应, 建立了基于相空间重构技术的径向基函数神经网络预测模型. 用该模型对第22, 23 太阳周黑子数平滑月均值进行逐月预报, 并与实测值进行比较. 结果表明, 预报的绝对误差可以控制在15.00 以内, 平均绝对误差分别为5.47, 2.83, 相对误差控制在15.00%以内, 平均相对误差分别为5.45%, 4.60%, 验证了该模型在预测太阳黑子数时具有较高的精度. 将该预测模型用于第24 太阳周黑子数平滑月均值预报, 做出了自2009 年1月到2019年12月共132 个月的黑子数平滑月均值的预报, 指出黑子数平滑月均值的最大值为104.77, 将出现的时间为2013年1月.     

Self-sustaining nonlinear dynamo process in Keplerian shear flows

A three-dimensional nonlinear dynamo process is identified in rotating plane Couette flow in the Keplerian regime. It is analogous to the hydrodynamic self-sustaining process in nonrotating shear flows and relies on the magnetorotational instability of a toroidal magnetic field. Steady nonlinear solutions are computed numerically for a wide range of magnetic Reynolds numbers but are restricted to low Reynolds numbers. This process may be important to explain the sustenance of coherent fields and turbulent motions in Keplerian accretion disks, where all its basic ingredients are present.     

Kinetic helicity,magnetic helicity and fast dynamo action

The influence of the flow helicity on kinematic fast dynamo action is considered. Three different flows are studied, possessing identical chaotic properties but very different distributions of helicity (maximal helicity, zero net helicity and zero helicity density). All three flows provide strong evidence of fast dynamo action, indicating that helicity is not a crucial feature of fast dynamo flows. Comparisons are made between the magnetic fields generated by the three flows and it is established how certain key quantities scale with the magnetic Reynolds number. In particular, it is shown that the relative magnetic helicity tends to zero as the magnetic Reynolds number tends to infinity.