A comparison of veloCity measurements from the CUTLASS Finland radar and the EISCAT UHF system   总被引：2，自引：0，他引：2  

J. A. Davies  M. Lester  S. E. Milan  T. K. Yeoman 《Annales Geophysicae》1999,17(7):892-902

The CUTLASS Finland radar, which comprises an integral part of the SuperDARN system of HF coherent radars, provides near continuous observations of high-latitude plasma irregularities within a field-of-view which extends over some four million square kilometres. Within the Finland radar field-of-view lie both the EISCAT mainland and EISCAT Svalbard incoherent scatter radar facilities. Since the CUTLASS Finland radar commenced operation, in February 1995, the mainland EISCAT UHF radar has been run in common programme 1 and 2 modes for a total duration exceeding 1000 h. Simultaneous and spatially coincident returns from these two radars over this period provide the basis for a comparison of irregularity drift veloCity and F-region ion veloCity. Initial comparison is limited to velocities from four intervals of simultaneous radar returns; intervals are selected such that they exhibit a variety of veloCity signatures including that characteristic of the convection reversal and a rapidly fluctuating veloCity feature. Subsequent comparison is on a statistical basis. The velocities measured by the two systems demonstrate reasonable correspondence over the veloCity regime encountered during the simultaneous occurrence of coherent and incoherent scatter; differences between the EISCAT UHF measurements of F-region ion drift and the irregularity drift velocities from the Finland radar are explained in terms of a number of contributing factors including contamination of the latter by E-region echoes, a factor which is investigated further, and the potentially deleterious effect of discrepant volume and time sampling intervals.  相似文献   

High-beta plasma blobs in the morningside plasma sheet   总被引：1，自引：0，他引：1  

G. Haerendel  W. Baumjohann  E. Georgescu  R. Nakamura  L. M. Kistler  B. Klecker  H. Kucharek  A. Vaivads  T. Mukai  S. Kokubun 《Annales Geophysicae》1999,17(12):1592-1601

Equator-S frequently encountered, i.e. on 30%0of the orbits between 1 March and 17 April 1998, strong variations of the magnetic field strength of typically 5–15-min duration outside about 9R_E during the late-night/early-morning hours. Very high-plasma beta values were found, varying between 1 and 10 or more. Close conjunctions between Equator-S and Geotail revealed the spatial structure of these “plasma blobs” and their lifetime. They are typically 5–10° wide in longitude and have an antisymmetric plasma or magnetic pressure distribution with respect to the equator, while being altogether low-latitude phenomena (<15°). They drift slowly sunward, exchange plasma across the equator and have a lifetime of at least 15–30 min. While their spatial structure may be due to some sort of mirror instability, little is known about the origin of the high-beta plasma. It is speculated that the morningside boundary layer somewhat further tailward may be the source of this plasma. This would be consistent with the preference of the plasma blobs to occur during quiet conditions, although they are also found during substorm periods. The relation to auroral phenomena in the morningside oval is uncertain. The energy deposition may be mostly too weak to generate a visible signature. However, patchy aurora remains a candidate for more disturbed periods.  相似文献   

电感耦合等离子体质谱法测定二氧化铀和八氧化三铀粉末中的杂质元素   总被引：4，自引：0，他引：4  

郭冬发  武朝辉  黄秋红  裴玲云  李振涛 《铀矿地质》1999,15(3):177-180

本文简述了等离子体质谱法测定二氧化铀和八氧化三铀粉末中的硼、钛、钒、钼、铬、锌、镉等７个痕量元素的方法。本方法采用ＴＢＰ萃取色层分离铀基体后,用高分辨等离子体质谱仪（ＩＣＰ－ＭＳ）测定多个痕量元素,测定下限达１×１０－９ｇ／ｇ,测定的相对标准偏差小于１５％。核工业１４个实验室比对试验结果表明,本方法结果准确可靠  相似文献   

Estimating biomass of phytoplankton in the Jiaozhou Bay Ⅰ.Phytoplankton biomass estimated from cell volume and plasma volume     

Sun Jun  Liu Dengyan  Qian Shuben 《海洋学报(英文版)》2000,19(2):97-110

Based on the data of the Jiaozbou Bay Ecosystem Dynamic Research,cell volume and surface area of 87 common phytoplankton species in China sea waters were calculated with assignment of the similar geometric form.The cell plasma volume,live weight,carbon mntent and nitrogen content were also calculated with the methods of Mullin et al.(1966),5trathmann(1967),Eppley et al.(1970),arid Taguchi(1976).After comparing these methods,we chose the method of Eppley et al.(1970) as the best method for calculating phytoplankton carbon content in China sea waters.  相似文献   

Stability of the line preserving flows     

Przemysław Figura 《地球物理与天体物理流体动力学》2017,111(6):508-526

We examine the equations that are used to describe flows which preserve field lines. We study what happens if we introduce perturbations to the governing equations. The stability of the line preserving flows in the case of the magneto-fluids permeated by magnetic fields is strictly connected to the non-null magnetic reconnection processes. In most of our study we use the Euler potential representation of the external magnetic field. We provide general expressions for the perturbations of the Euler potentials that describe the magnetic field. Similarly, we provide expressions for the case of steady flow as well as we obtain certain conditions required for the stability of the flow. In addition, for steady flows we formulate conditions under which the perturbations of the external field are negligible and the field may be described by its initial unperturbed form. Then we consider the flow equation that transforms quantities from the laboratory coordinate system to the related external field coordinate system. We introduce perturbations to the equation and obtain its simplified versions for the case of a steady flow. For a given system, use of this method allows us to simplify the considerations provided that some part of the system may be described as a perturbation. Next, to study regions favourable for the magnetic reconnection to occur we introduce a deviation vector to the basic line preserving flows condition equation. We provide expressions of the vector for some simplifying cases. This method allows us to examine if given perturbations either stabilise the system or induce magnetic reconnection. To illustrate some of our results we study two examples, namely a simple laboratory plasma flow and a simple planetary magnetosphere model.  相似文献   

大尺度场向电流及其与单色极光电子的联系--Swarm卫星观测          下载免费PDF全文

张琬  蔡红涛  周康俊  张宏  高顺祖 《地球物理学报》2020,63(4):1262-1270

Swarm卫星A/C在480km左右高度伴飞,通过二者磁场观测数据,可在不需假设无限大垂直电流片的情况下更加真实地计算出场向电流(FAC).本文利用最新的Swarm观测数据,研究了大尺度场向电流的时空分布特征,及其对行星际条件的依赖;结合极光沉降粒子时空分布信息,探究了场向电流可能载流子及其源区.分析发现:(1)IMF Bz分量主要控制FAC的强度大小,By分量主要改变FAC的结构与分布,最为明显的是0区FAC;(2)昏侧1区上行FAC与单色极光电子的高发区域具有较高的重合度,且在不同行星际条件下均表现出相类似的纬度分布;(3)在上述区域内,FAC密度与单色极光电子能通量表现出较好的相关性.这表明单色极光电子对昏侧1区上行电流起着重要贡献.  相似文献   

用粒子模拟方法研究离子声波     

黄宇  宋其武 《天文学报》2019,60(5):22-33

<正>向传播朗缪尔波被离子声波散射是太阳射电Ⅲ型暴基波和谐波激发的重要过程.使用粒子模拟方法对电子束流激发朗缪尔波的过程进行了模拟,同时对产生的反向朗缪尔波、朗缪尔波2次谐波和朗缪尔波通过非线性过程产生的离子声波的性质进行了分析研究.为了更好地研究离子声波,模拟时单独计算了由离子扰动引起的电场.模拟计算了不同初始参数下产生的离子声波强度,发现离子的温度和质量对离子声波的产生有重要作用,验证了反向朗缪尔波与离子声波的相关性.同时在模拟中验证了朗缪尔波的衰变过程,确认了离子声波对反向朗缪尔波的放大作用.  相似文献   

Nonlinear acoustic waves in a collisional self-gravitating dusty plasma     

郭志荣  杨增强  殷保祥  孙茂珠 《海洋学报(英文版)》2010,29(11)

Using the reductive perturbation method, we investigate the small amplitude nonlinear acoustic wave in a collisional self-gravitating dusty plasma. The result shows that the small amplitude dust acoustic wave can be expressed by a modified Korteweg-de Vries equation, and the nonlinear wave is instable because of the collisions between the neutral gas molecules and the charged particles.  相似文献   

基于等离子体增强化学气相沉积技术的光电子器件多层抗反膜的设计和制作     

袁贺  孙长征  徐建明  武庆  熊兵  罗毅 《海洋学报》2010,32(10):7239-7244

针对光电子器件端面抗反镀膜的要求,研究了基于等离子体增强化学气相沉积(PECVD)技术的多层抗反膜的设计和制作.首先,对影响SiN_x折射率的因素进行了实验研究,确定了具有大折射率差的SiO₂/SiN_x材料的PECVD沉积条件.根据理论计算分析,设计了四层SiO₂/SiN_x抗反膜结构,能够在70 nm的波长范围内实现低于10^-4的反射率  相似文献   

强场和弱场侧超声分子束注入对加料的影响     

焦一鸣  姚良骅  冯北滨  陈程远  周艳  石中兵  董家齐  段旭如 《海洋学报》2010,32(10):7191-7197

报道了HL-2A装置最新的实验结果,讨论并研究了超声分子束的注入位置对分子束在等离子体中的消融和穿透的影响,其中包括电离后的分子束粒子在磁场梯度作用和 E × B 漂移下的加速或减速及由此形成的冷通道效应.研究结果表明,磁场梯度和 E × B 漂移对于超声分子束的加料效果、消融和穿透有着重要的作用.强场侧注入可使电离后的电子和离子更深地进入等离子体芯部.这些研究对于更好地理解超声分子束与等离子体的相互作用和优化设计加料系统有一定作用.  相似文献