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581.
给出了1997年1月6—11日日地连接事件的太阳风和行星际扰动及由此产生的地磁扰动特征.利用这些资料对磁暴-环电流-对流电场的分析表明,磁暴主相(或环电流)的开始主要是IMF南向分量形成的对流电场直接驱动的结果;对流电场在磁暴主相的形成中有极为重要的作用;但在主相发展的不同阶段作用不同  相似文献   
582.
The data presented in this work describes the diurnal and seasonal variation in hmF2, NmF2, and the electrojet current strength over an African equatorial station during a period of low solar activity. The F2 region horizontal magnetic element H revealed that the Solar quiet Sq(H) daily variation rises from early morning period to maximum around local noon and falls to lower values towards evening. The F2 ionospheric current responsible for the magnetic field variations is inferred to build up at the early morning hours, attaining maximum strength around 1200 LT. The Sq variation across the entire months was higher during the daytime than nighttime. This is ascribed to the variability of the ionospheric parameters like conductivity and winds structure in this region. Seasonal daytime electrojet (EEJ) current strength for June solstice, March and September equinoxes, respectively had peak values ranging within 27–35 nT (at 1400 LT) , 30–40 nT (at 1200 LT) and 35–45 nT (at 1500 LT). The different peak periods of the EEJ strength were attributed to the combined effects of the peak electron density and electric field. Lastly, the EEJ strength was observed to be higher during the equinoxes than the solstice period.  相似文献   
583.
We present the results of three years of continuous operations and the principal characteristics of our new 3He neutron monitors installed in the Chilean Network of Cosmic-Ray Observatories. During the years 2004 and 2005, we began the construction of this International Geophysical Year (IGY)-type 3He neutron monitor, with the intention of replacing the older proportional tubes of the BF3. These new monitors are installed in stations at locations ranging from the near-equatorial zone to the Antarctic zone. As a reference system, we used our own BF3 neutron monitors and previously complemented the collected data with a Monte Carlo simulation for the proton-yield function response of the Putre neutron monitor. Herein, we present for the first time the data obtained from our new high-mountain observatory located in the Altiplanic zone.  相似文献   
584.
In this paper, we have improved the capabilities of a low dimensional nonlinear dynamical model called WINDMI to determine the state of the global magnetosphere by employing the magnetotail (MT) index as a measurement constraint during large geomagnetic storms. The MT index is derived from particle precipitation measurements made by the NOAA/POES satellites. This index indicates the location of the nightside ion isotropic boundary, which is then used as a proxy for the strength of the magnetotail current in the magnetosphere. In Asikainen et al. (2010), the contribution of the tail current to the Dst index is estimated from an empirical relationship based on the MT index. Here the WINDMI model is used as a substitute to arrive at the tail current and ring current contribution to the Dst index, for comparison purposes. We run the WINDMI model on 7 large geomagnetic storms, while optimizing the model state variables against the Dst index, the MT index, and the AL index simultaneously. Our results show that the contribution from the geotail current produced by the WINDMI model and the MT index are strongly correlated, except during some periods when storm time substorms are observed. The inclusion of the MT index as an optimization constraint in turn increases our confidence that the ring current contribution to the Dst index calculated by the WINDMI model is correct during large geomagnetic storms.  相似文献   
585.
由于传统提供附加磁场的液冷铜线圈存在体积大、质量大、电耗大等显著缺点,因此电流密度高、体积小、损耗低的高温超导(HTS)磁体在附加场磁等离子发动机(AF MPDT)上的应用受到了广泛的关注。然而由于超导材料的临界特性,HTS磁体容易受到外部磁场的影响而发生失超。文章通过对MPDT放电回路的简化,采用仿真和试验的方法来分析简化回路通电时激发的磁场,并研究其对外围HTS磁体的影响程度。仿真结果表明,MPDT放电室内部磁场以周向磁场为主,且由于阳极壁面电流对内部磁场的屏蔽作用,使得外部几乎没有磁场分布。试验结果和仿真也取得了良好的一致性,因此在设计超导磁喷管时几乎可以不考虑来自MPDT放电室磁场的影响。该研究为HTS磁体在AF MPDT上的应用提供了参考。  相似文献   
586.
二总线火灾报警系统是由内一些生产厂家近年推出的一种高新技术产品,相对一般三总线、四总线火灾报警系统来说,它给工程设计,安装及使用带来极大方便,但也存在单回路带栽能力普遍低于三总线和四总线的缺点。本文从尽可能地减少探测器的工作电流入手,来提高二总线火灾报警系统的带载能力,达到了预期的效果。  相似文献   
587.
从工程应用角度出发,分析了振幅误差和相位误差对雷达性能的影响。为了简化起见,只考虑地杂波和单频干扰,且不考虑接收机的热噪声,文中讨论了单脉冲测角精度,时间域中滤波器抑制杂波的能力和空间域中滤波器抑制有源干扰的能力等6个有关雷达设计中的具体问题,结论简明,并给出了曲线提供参考。  相似文献   
588.
罗五美 《飞行力学》1995,13(3):84-89
介绍对一架带有纵向数字飞控系统的K8飞机自由飞模型进行的放宽静稳定度的试验研究,获取利用模型进行此种试验的可行性和实施方法,模型采用了四种重心构型;正常重心,中立重心,后移2%bA和后移4%ba。模型上加装了控制增稳装置,进行了控制律设计,取得较为满意的试验结果,地面仿真试验结果与飞行试验也是基本一致的,试验达到预期的目的。  相似文献   
589.
《中国航空学报》2023,36(1):152-165
Numerous investigations have been conducted to understand the wall effects on rotors. The purpose of this study is to further investigate the aerodynamic performance of revolving wings, especially when it is very close to the ground and ceiling (i.e., less than half the wingspan) at low Reynolds numbers. Hence, the ground and ceiling effect for hovering micro revolving wings at low Reynolds numbers are investigated by improving the theoretical models. The theoretical model for the ground effect is established based on the wall-jet assumption, and that for the ceiling effect is improved by considering the uneven spanwise distribution of induced velocity. These two models are validated by comparing the results of experiments and CFD simulations with the Lattice-Boltzmann Method (LBM). Both ground and ceiling effects are found helpful to enhance the thrust, especially with small wing-wall distances, by making a difference to the induced velocity and the pressure distribution. By comparing the thrust generation and aerodynamic efficiency between the ground and ceiling effects, the former is found more helpful to the thrust augmentation, and the latter is more beneficial for the aerodynamic efficiency promotion.  相似文献   
590.
运载火箭新型地面测试发控系统构想   总被引:4,自引:0,他引:4  
张晨光  杨华  杨军 《宇航学报》2005,26(3):249-252
为了提高我国地面测试发控系统整体水平,在借鉴和继承国内外成熟型号地面测试发控系统优秀设计思想的基础上,结合现代运载火箭技术需求,通过对总体设计、任务和功能分析、框架组建等方面的分析和论述,提出了新型运载火箭地面测试发控系统方案构想。此方案在总体设计思想、系统框架结构设计、应用模式上提出新的思路,对于适应未来运载火箭发射要求提供了技术途径。  相似文献   
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