Dipolarization fronts in the magnetotail plasma sheet   总被引：1，自引：0，他引：1  

A. Runov  V. Angelopoulos  V.A. Sergeev  Y. Nishimura  H.U. Frey  D. Larson  K.-H. Glassmeier  M. Connors  C.T. Russell 《Planetary and Space Science》2011,59(7):517-525

We present a THEMIS study of a dipolarization front associated with a bursty bulk flow (BBF) that was observed in the central plasma sheet sequentially at X=−20.1, −16.7, and −11.0R_E. Simultaneously, the THEMIS ground network observed the formation of a north-south auroral form and intensification of westward auroral zone currents. Timing of the signatures in space suggests earthward propagation of the front at a velocity of 300 km/s. Spatial profiles of current and electron density on the front reveal a spatial scale of 500 km, comparable to an ion inertial length and an ion thermal gyroradius. This kinetic-scale structure traveled a macroscale distance of 10R_E in about 4 min without loss of coherence. The dipolarization front, therefore, is an example of space plasma cross-scale coupling. THEMIS observations at different geocentric distances are similar to recent particle-in-cell simulations demonstrating the appearance of dipolarization fronts on the leading edge of plasma fast flows in the vicinity of a reconnection site. Dipolarization fronts, therefore, may be interpreted as remote signatures of transient reconnection.  相似文献   

等离子体片离子分界线的模拟研究     

丁维贞  曹晋滨 《地理学报》2013,1(1):1505-1514

等离子体片离子向内磁层的渗透在亚暴和磁暴过程中都起到了重要作用.以往对于等离子体片离子向内磁层的渗透都是通过固定磁矩的磁层离子漂移轨道理论来进行的.本文将过去的(U,B)空间中固定磁矩的磁层离子漂移轨道理论扩展为固定能量的磁层离子漂移轨道理论,讨论了等离子体片质子在向地球输运过程中,不同能量的质子开放轨道和封闭轨道的分界线的特性,及其随Kp指数的变化.在高能端,随着能量的升高,等离子体片质子分界线地心距离逐渐增大,且分界线的晨侧地心距离远远大于昏侧的地心距离.在低能端,随着质子能量的降低,质子分界线地心距离逐渐增大,且其分界线的昏侧地心距离要大于晨侧的地心距离.模拟结果还显示随着Kp指数的增强,等离子体片中不同能量的质子分界线都向地球移动.但在低能端和高能端,质子分界线的行为是不一样的.在低能端,随着Kp指数的增大,质子内边界形状基本保持不变.但在高能端,随着Kp指数的增大,质子内边界形状也将发生变化.在E=20 keV,Kp=6和E=10 keV,Kp=3两种情况,质子分界线甚至出现了两个分离的区域,一个是环绕地球的封闭轨道区域,一个是晨侧孤立的锥型区域.等离子体片能量为E的质子的内边界就是具有不同磁矩的Alfven层上能量为E的点的连线.TC-1热离子谱仪对等离子体片离子内边界的观测显示模拟结果与观测结果符合得很好.  相似文献   

利用卫星和GPS观测研究低纬局部等离子体浓度增强现象   总被引：1，自引：0，他引：1       下载免费PDF全文

陈艳红  龚建村  马冠一  黄文耿  刘四清 《地球物理学报》2010,53(12):2787-2795

本文同时利用DMSP、ROCSAT-1卫星数据和地基的GPS观测数据,研究一种与低纬等离子体泡相伴随的局部等离子体浓度增强现象.地基GPS的观测表明电离层总电子含量(TEC)也能反映这种等离子体浓度增强.通过4个观测事例的详细分析表明:这种等离子体浓度增强主要出现在磁纬±10°～±20°的局部区域,有时在近磁赤道区和中纬地区的电离层顶部也能观测到;与等离子体泡的出现规律相似,这种等离子体浓度增强主要出现在地方时21∶00以后,并在午夜后也能观测到.当等离子体浓度增强和等离子体泡发生时,在午夜前一般对应着背景垂直速度明显向上的扰动,在午夜后一般处于等离子体垂直速度下降至反向前的时间段,表明东向电场对于低纬不规则体的产生有非常重要的作用.  相似文献   

高能电子爆发与绕月卫星表面电位大幅下降的联动效应   总被引：2，自引：0，他引：2       下载免费PDF全文

王馨悦  张爱兵  荆涛  H. Reme  孔令高  张珅毅  李春来 《地球物理学报》2016,59(10):3533-3542

"嫦娥"一号、二号绕月飞行经历地球磁尾边界层区域时,分别在2007年11月26日—2008年2月5日和2010年10月3日—2011年2月28日,发现了15次月球轨道0.1~2 MeV电子急剧增加(Bursts of 0.1~2 MeV Energetic Electrons,BEE),卫星周围等离子体离子加速的现象.统计研究表明,这类现象发生在稳定太阳风和弱行星际磁场条件下,且无显著空间环境扰动事件发生时,离子的加速滞后于高能电子爆发,离子能量的变化与高能电子通量的时间演化正相关,地球磁鞘内侧或边界层过渡区域是该类现象的高发区,离子能量增加时卫星表面电位大幅下降可达负几千伏.为了研究高能电子爆发与绕月卫星表面电位变化的关系及其对月球表面电位的影响,本文用电流平衡法建立绕月卫星和月球表面充电模型,并假设能量电子(2eV~2 MeV)满足幂律谱的分布,模拟急剧增加的能量电子对卫星和月球表面电位的影响.模拟结果表明,能量电子急剧增加使得绕月卫星和月球表面电位大幅下降;能量电子总流量1011 cm-2时,绕月卫星和月球表面充电电位可达负上千伏;月球充电到大的负电位的时间仅为卫星充电时间的1/10.鉴于高能电子急剧增加事件的高发生率(~125次/年),能量电子急剧增加使得绕月卫星表面电位大幅下降的发生率应大于实测等离子体离子加速现象的发生率(~25次/年).  相似文献   

Automated Determination of Sulfadiazine in Water,Fish Plasma and Muscle by HPLC with On‐Line Column‐Switching          下载免费PDF全文

Muhammet Altunok  Armin König  Waleed M.M. Mahmoud Ahmed  Tarek Haddad  Tibiriçá G. Vasconcelos  Klaus Kümmerer 《洁净——土壤、空气、水》2016,44(8):967-974

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Current and Future Applications of 3-D Global Earth-Ionosphere Models Based on the Full-Vector Maxwell’s Equations FDTD Method     

Jamesina J. Simpson 《Surveys in Geophysics》2009,30(2):105-130

Advances in computing technologies in recent decades have provided a means of generating and performing highly sophisticated computational simulations of electromagnetic phenomena. In particular, just after the turn of the twenty-first century, improvements to computing infrastructures provided for the first time the opportunity to conduct advanced, high-resolution three-dimensional full-vector Maxwell’s equations investigations of electromagnetic propagation throughout the global Earth-ionosphere spherical volume. These models, based on the finite-difference time-domain (FDTD) method, are capable of including such details as the Earth’s topography and bathymetry, as well as arbitrary horizontal/vertical geometrical and electrical inhomogeneities and anisotropies of the ionosphere, lithosphere, and oceans. Studies at this level of detail simply are not achievable using analytical methods. The goal of this paper is to provide an historical overview and future prospectus of global FDTD computational research for both natural and man-made electromagnetic phenomena around the world. Current and future applications of global FDTD models relating to lightning sources and radiation, Schumann resonances, hypothesized earthquake precursors, remote sensing, and space weather are discussed.

Jamesina J. SimpsonEmail:

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地球磁尾中重联产生的磁流通管的运动   总被引：1，自引：1，他引：0       下载免费PDF全文

杨亚芬  陈出新 《地球物理学报》2009,52(5):1131-1137

本文通过MHD理论研究了细磁流通管在二维静止平衡介质中的运动.用地球磁尾中的一维细丝来表示流通管,通过数值模拟可以得到细丝随时间变化的一些性质.重联产生的细丝磁场比周围磁场偶极性更强,运动时表现出了很强的地向流.结果还显示了阿尔芬波、慢激波等MHD波从磁层的赤道面传播到地球电离层上并部分地反射回来.细丝在电离层上的足点的赤道向运动滞后于赤道面上的地向运动.虽然在模拟中细丝的初始等离子体压强低于周围压强,但是当它开始迅速向地球方向运动时,它的等离子体压强很快上升到与周围压强相当,甚至有时候大于周围压强的值.  相似文献   

The role of critical velocity ionization phenomena in the atmosphere of Io     

Prasad C. Debi 《Earth, Moon, and Planets》1995,71(1-2):65-71

The Alfvén's critical ionization velocity (CIV) have been observed in a number of laboratory and space experiments. In the Io-torus system, relative velocity of the plasma species in the torus with respect to the neutral species in the Io's atmosphere and neutral cloud exceeds the critical velocity required for CIV. Townsand condition is satisfied up to 6r _io , in the neutral cloud when Io passes through the torus. In this paper it is shown that during the passage of Io through the plasma torus, apart from critical velocity and Townsand condition, a number of other requirements are also satisfied. Therefore, it is concluded that, the CIV mechanism must play an important role in ionizing the neutral cloud and enriching the plasma torus.  相似文献   

EISCAT雷达观测到的极区电离层等离子体反常对流          下载免费PDF全文

马淑英  刘鹏  刘会欣  徐继生  K Schlegel 《地球物理学报》2001,44(4):446-453,T001

综合分析EISCAT雷达与卫星当地测量数据,并利用磁层磁场模式对磁力线进行追踪,研究了发生在极光椭圆朝极盖边界附近电离层中,一例反常的背离太阳流动的强等离子体对流事件,及相关的太阳风-磁层-电离层耦合过程.结果表明,磁暴期间IMFBz指向南时观测到这一反常高速对流,及其相应的等离子体性态特征,很可能是向阳侧磁层顶磁重联过程在电离层中的印记.  相似文献   

A model cosmology based on gravity-electromagnetism unification     

John E. Brandenburg 《Astrophysics and Space Science》1995,227(1-2):133-144

In this article the GEM (Brandenburg, 1992; Brandenburg, 1988) theory is applied to the problem of the cosmos in which most of the matter is hydrogen, spacetime is flat, and a Cosmic Background Radiation CBR field exists. Using the two postulates of the GEM theory: 1. That gravity fields are equivalent to an array ofE ×B drifts or a spacially varying Poynting field, such that spacetime is determined by EM fields so that the stress tensor of ultrastrong fields is self-canceling; 2. That EM and gravity fields and protons and electrons are unified at the Planck scale of lengths and energies and split apart to form distinct fields and separate particles at the Mesoscale of normal particle rest energies and classical radii. A new derivation is made of the formula forG found previously:G =e ²/(m _p m _e ) exp(-2R ^1/2) = 6.668 × 10^–8 dynes cm² g^–2wherem _p andm _e are the proton and electron masses respectively,R =m _p /m _e and is the fine structure constant, shows that quantum processes may occur which make the vacuum unstable to appearance of hydrogen thus allowing matter creation and a steady state universe to occur. The value for the Hubble Time calculated from this model isT _o = (3/((2)(R ^1/2)⁴))^1/3(r _e /c)(e ²/Gm _p m _e )= 19 Gyr wherer _e =e ² / (m _e c ²)and follows the form first hypothesized by Dirac(1937). The CBR is traced to this process of matter creation and its temperature is calculated as beingT _CBR = ((3/4)Gm _e ² c/( ² _o ))^1/4 = 2.66K where is the Thomson cross section of the electron and _o is the Stefan-Boltzman constant.  相似文献