Magnetic field fossilization and tail reconfiguration in Titan's plasma environment during a magnetopause passage: 3D adaptive hybrid code simulations     

Joachim Müller  Sven Simon  Karl-Heinz Glassmeier  Joachim Saur  Gavin J. Pringle 《Planetary and Space Science》2010,58(12):1526-1546

We present a hybrid simulation study (kinetic ions, fluid electrons) of Titan's plasma interaction during an excursion of this moon from Saturn's magnetosphere into its magnetosheath, as observed for the first time during Cassini's T32 flyby on 13 June 2007. In contrast to earlier simulations of Titan's plasma environment under non-stationary upstream conditions, our model considers a difference in the flow directions of magnetospheric and magnetosheath plasma. Two complementary scenarios are investigated, with the flow directions of the impinging magnetospheric/magnetosheath plasmas being (A) antiparallel and (B) parallel. In both cases, our simulations show that due to the drastically reduced convection speed in the slow and dense heavy ion plasma near Titan, the satellite carries a bundle of “fossilized” magnetic field lines from the magnetosphere in the magnetosheath. Furthermore, the passage through Saturn's magnetopause goes along with a disruption of Titan's pick-up tail. Although the tail is not detached from the satellite, large clouds of heavy ion plasma are stripped of its outer flank, featuring a wave-like pattern. Whereas in case (B) under parallel flow conditions there is only a small retardation of about 5 min between the passage of Titan through the magnetopause and the reconfiguration of the pick-up tail, the tail reconfiguration in the case (A) scenario is completed not until 25 min after the magnetopause passage. The lifetime of fossil fields in the moon's ionosphere is approximately 25 min, regardless of whether parallel or antiparallel flow conditions are applied.  相似文献   

Seas under ice: Stability of liquid-water oceans within icy worlds     

Javier Ruiz  Alberto G. Fairén 《Earth, Moon, and Planets》2005,97(1-2):79-90

The present-day existence of internal oceans under the outer ice shell of several icy satellites of the Solar System has been recently proposed. The presence of antifreeze substances decreasing ice’s melting point (and tidal heating in Europa’s case) has been generally believed to allow the stability of such oceans; limited cooling of the water (ice plus liquid) layer, due to stability against convection or to stagnant lid convection in the icy shell, have been also considered. Here we propose that even pure liquid-water oceans could survive today within several icy worlds, and we consider some factors affecting thermal modeling in these bodies. So, the existence of such oceans would be a natural consequence of the physical properties of water ice, independently from the addition of antifreeze substances or any other special conditions. The inclusion of these substances would contribute to expand the conditions for water to stay liquid and to increase ocean’s volume.  相似文献   

内蒙小松山基性－超基性岩体的岩石谱系单位划分     

李厚民  李伍平  赵东宏 《地球科学与环境学报》1995,(3)

本文对贺兰山北部以小松山为主的基性－超基性岩体进行了岩石谱系单位划分，建立了小松山基性岩超单元和超基性岩超单元。  相似文献   

凤凰山矿田成矿地质体三维结构与控矿地质因素分析   总被引：2，自引：0，他引：2  

毛先成  唐艳华  赖健清  邹艳红  陈进  彭省临  邵拥军 《地质学报》2011,85(9):1507-1518

安徽铜陵凤凰山铜矿正面临资源保有程度严重不足的问题,建立凤凰山矿田成矿地质体三维结构和控矿地质因素模型,开展矿田深部隐伏矿体立体定位预测具有重要的现实意义.凤凰山矿田矿床矿体的定位主要受接触带和断裂构造的复合控制,新屋里岩体与围岩呈侵入接触,局部地段超覆于围岩之上,接触带的形态和产状控制了矿体的空间分布.在分析矿田地质...  相似文献   

扎龙湿地水体遥感提取过程中云阴影去除方法研究   总被引：2，自引：1，他引：1  

郑晓燕  张艳红  刘万崧 《湿地科学》2010,8(1):21-27

以扎龙湿地为研究区,利用空间分辨率高、纹理信息丰富、定位精度高和购买价格相对低廉的ALOS遥感影像,测定了研究区水体等5种典型地物和云阴影的波谱亮度值;根据水体和云阴影的光谱特征,利用阈值法对近红外波段ALOS影像进行阈值处理,将包含云阴影信息的水体信息提取出来;基于ALOS彩色影像,再采用决策树方法自动提取湿地水体信息,同时将云阴影信息去除,并再补充提取因去除云阴影而损失的水体信息;与目视解译结果相比,用本研究方法得到的研究区湿地水体信息精度高于85%。近红外波段阈值法和彩色影像决策树法相结合的方法是一种能有效去除云阴影而高精度获取湿地水体信息的方法。  相似文献   

采场结构体回采可移动性分析     

陈庆发  牛文静 《岩土力学》2016,37(5):1458-1466

采场范围内存在的结构体严重影响地下矿山安全生产,分析不同回采顺序下采场结构体可移动性具有重要意义。以块体理论为基础,结合空场法开采的采场空间属性,分析了结构体在采场内的一般嵌套模式。运用GeneralBlock程序建立了采场结构体模型,对采场内结构体的类型、体积和位置等元素进行了解构。利用矢量方法分析了不同回采顺序下采场结构体可移动性,并利用力学方法分析了考虑岩桥破坏时的矢量不可动结构体的回采移动性,推导了结构体破坏岩桥移动的条件公式。以铜坑矿锌多金属矿体1#矿块采场为样本,进行了回采可移动性实例分析,结果表明：一端至另一端后退回采时,4个结构体滑动;中间至两端后退回采时,7个结构体滑动,1个结构体破坏岩桥后滑动;上向水平分层回采时,4个结构体滑动,2个结构体掉落。研究成果可为地下矿山裂隙矿岩空场法回采顺序的合理选择及采场安全管理提供技术指导。  相似文献   

鲁东文登地区文登型(超单元)花岗岩体的SHRIMP锆石年代学   总被引：1，自引：0，他引：1       下载免费PDF全文

王世进  万渝生  宋志勇  王伟  董春艳  张贵丽 《山东国土资源》2012,28(2):1-5,10

文登岩体主要岩性为不同粒度的二长花岗岩,原划为三叠纪。根据新测的锆石SHRIMP U-Pb年龄为(167±3)Ma,(167±2)Ma,(157.1±1.4)Ma,结合野外接触关系改划为侏罗纪。文登花岗岩体属侏罗纪钙碱系列的侵入体,主要显示长英质陆壳深熔花岗岩的特征。推断其形成于中下地壳深度,可能来源于加厚陆壳的部分熔融,是加厚下地壳的拆沉作用的产物,而且可能标志着中国东部岩石圈减薄的开始。  相似文献   

流域生态补偿研究现状及关键问题剖析   总被引：3，自引：0，他引：3  

乔旭宁  杨永菊  杨德刚 《地理科学进展》2012,31(4):395-402

在流域,因竞争性用水导致上下游之间、人类发展与生态环境之间的矛盾日益尖锐,急需建立健全流域生态补偿机制.通过对国内外流域生态补偿研究进展进行梳理,发现流域生态补偿研究主要集中在流域尺度的补偿计划实施评价、补偿尺度的选择、补偿标准的测算、生态补偿与减少贫困关系、流域生态补偿的空间差异性等方面,其关键问题在于生态补偿主体和对象的确定以及补偿标准的制定;研究认为通过流域断面水量水质及相关利益分析方法来确定补偿主体和对象;而补偿标准则以流域上下游生态损益、机会成本、居民支付意愿分别作为补偿上限、参考值和下限来综合确定.以此为基础,构建流域多种生态要素、多元主体间的流域生态补偿机制研究框架.最后,就流域生态补偿机制构建过程中有待解决的科学问题进行了讨论.  相似文献   

The relativistic factor in the orbital dynamics of point masses     

Federico Benitez  Tabaré Gallardo 《Celestial Mechanics and Dynamical Astronomy》2008,101(3):289-307

There is a growing population of relativistically relevant minor bodies in the Solar System and a growing population of massive extrasolar planets with orbits very close to the central star where relativistic effects should have some signature. Our purpose is to review how general relativity affects the orbital dynamics of the planetary systems and to define a suitable relativistic correction for Solar System orbital studies when only point masses are considered. Using relativistic formulae for the N body problem suited for a planetary system given in the literature we present a series of numerical orbital integrations designed to test the relevance of the effects due to the general theory of relativity in the case of our Solar System. Comparison between different algorithms for accounting for the relativistic corrections are performed. Relativistic effects generated by the Sun or by the central star are the most relevant ones and produce evident modifications in the secular dynamics of the inner Solar System. The Kozai mechanism, for example, is modified due to the relativistic effects on the argument of the perihelion. Relativistic effects generated by planets instead are of very low relevance but detectable in numerical simulations.  相似文献   

吉南太古宙岩群中的大型构造置换及其对BIF矿体的控制   总被引：5，自引：2，他引：3       下载免费PDF全文

刘如琦 《地质科学》2004,39(3):407-415

以吉林省白山市板石沟铁矿区为典型实例,系统地论述了太古宙岩群中广泛发育的大型和区域性构造置换的几何特征和对BIF矿体的控制规律。本区构造置换主要表现为:在紧闭同斜褶皱发育的持续变形过程中形成S₁≈S₀,并伴有钩状褶皱、石香肠构造和各类型线理的生成。按照主构造面均匀性法则,划分了构造均匀区段,并对其中8个区段(Ⅰ～Ⅷ)进行了详细的SFLπ组构分析。基于构造置换规律研究,提出本区褶皱轴与包络线双向找矿的理论与方法,经工程验证,取得显著的经济效益。  相似文献