高精度长寿命固体润滑滚动轴承弹性加载方式

文中讨论了空间飞行器高精度、长寿命、高可靠性活动部件——固体润滑滚动轴承的一种预加轴向载荷的方式。实验证明经过良好的设计和装调,采用转移膜润滑工艺,加以准确合适的均匀的轴向预载,可以使轴承保持低且较稳定的摩擦力矩、高的旋转精度和较长的寿命。     

日冕膨胀和太阳角动量向行星际空间的转移

本文讨论了日冕膨胀中的角动量问题。利用大量I型彗尾资料的计算,证实了日冕膨胀中方位分量的存在;它不仅是随机量,而是具有大小为9.8km/s的定常量。太阳演化到主序星阶段以来,由于日冕膨胀丢失了80％的角动量,太阳自转角速度正以指数律下降。因此,这将对太阳动力演化起到很大的影响。     

非晶态(Fe_(0.5)Ni_(0.5))_(80-x)Cr_xP_(14)B_6合金薄带的磁场敏感特性的研究

本文对非晶态(Fe_(0.5)Ni_(0.5))_(80-x)Cr_xP_(14)B_6(x=0,1,2,3,4,6,10)合金薄带样品的室温直流磁场敏感特性进行了测量。结果表明,在几十个A/m范围的外磁场内,样品具有开关型磁场敏感特性。对影响开关特性的三个因素进行了一些讨论。     

磁壳参数L与磁暴Dst指数和行星际条件的关系

用磁坐标L-/A来描述地球近地空间粒子特性和卫星位置是近年来空间物理探测研究和数据分析中的一个新趋势.利用T96磁场模型计算了L值,并比较了在地球磁层剧烈活动期间和不同行星际条件下,用偶极子模型,国际参照磁场(IGRF)模型,和T96磁场模型这三种方式计算得到的地球表面L-A磁坐标之间的区别.在地磁纬度大于30°时偶极子近似和IGRF磁场模型计算得到的L值差别开始增大.在地磁纬度大于50°时,用IGRF磁场模型和T96磁场模型计算得到的L值差别开始增大.由于T96磁场模型引入了行星际磁场南北和东西分量,计算的L值包含了行星际条件的影响,并具有了随地方时变化的特性.本工作对于辐射带粒子动态模式的建立,以及正确理解卫星磁坐标位置等具有重要意义.     

关于IMF北向分量特强时的太阳风－磁层－电离层耦合

关于ＩＭＦ北向分量特强时的太阳风－磁层－电离层耦合沈长寿，资民筠（北京大学地球物理系，１００８７１）（中国艺术研究院，北京）关键词行星际磁场，太阳风－磁层能量耦合函数为检验Ａｋａｓｏｆｕ提出的能量融合函数“’在ＢＺ强北向时能否反映太阳风与磁层扰动间的...     

Coupling of the interstellar and interplanetary magnetic fields at the heliospheric interface: The effect of neutral hydrogen atoms

We present numerical results showing the effect of neutral hydrogen atoms on the solar wind (SW) interaction with the local interstellar medium (LISM), where the interstellar magnetic field (ISMF) is coupled to the interplanetary magnetic field (IMF) at the surface of the heliopause. The IMF on the inner boundary surrounding the Sun is specified in the form of a Parker spiral and self-consistently develops in accordance with the SW motion inside the heliopause. The model of the SW–LISM interaction involves both plasma and neutral components which are treated as fluids. The configuration is chosen where the ISMF is orthogonal to the LISM velocity and tilted 60° to the ecliptic plane. This orientation of the magnetic field is a possible explanation of the 2–3 kHz emission data which is believed to originate ahead of the heliopause. It is shown that the topology of the heliospheric current sheet is substantially affected by the ISMF. The interaction pattern dependence on the neutral hydrogen density is analyzed.     

What is the role of magnetic null points in large flares?

We have performed the analysis of the magnetic topology of active region NOAA 10486 before two large flares occurring on October 26 and 28, 2003. The 3D extrapolation of the photospheric magnetic field shows the existence of magnetic null points when using two different methods. We use TRACE 1600 Å and 195 Å brightenings as tracers of the energy release due to magnetic reconnections. We conclude on the three following points:

1. The small events observed before the flares are related to low lying null points. They are long lasting and associated with low energy release. They are not triggering the large flares.

2. On October 26, a high altitude null point is found. We look for bright patches that could correspond to the signatures of coronal reconnection at the null point in TRACE 1600 Å images. However, such bright patches are not observed before the main flare, they are only observed after it.

3. On October 28, four ribbons are observed in TRACE images before the X17 flare. We interpret them as due to a magnetic breakout reconnection in a quadrupolar configuration. There is no magnetic null point related to these four ribbons, and this reconnection rather occurs at quasi-separatrix layers (QSLs).

We conclude that the existence of a null point in the corona is neither a sufficient nor a necessary condition to give rise to large flares.     

Influence of Fast Global Variations of Solar Magnetic Fields on Space Weather in Cycle 23

It is established that the large-scale and global magnetic fields in the Sun's atmosphere do not change smoothly, and long-lasting periods of gradual variations are superseded by fast structural changes of the global magnetic field. Periods of fast global changes on the Sun are accompanied by anomalous manifestations in the interplanetary space and in the geomagnetic field. There is a regular recurrence of these periods in each cycle of solar activity, and the periods are characterized by enhanced flaring activity that reflects fast changes in magnetic structures. Is demonstrated, that the fast changes have essential influencing on a condition of space weather, as most strong geophysical disturbances are connected to sporadic phenomena on the Sun. An explanation has been offered for the origin of anomalous geomagnetic disturbances that are unidentifiable in traditionally used solar activity indices. Is shown, main physical mechanism that leads to fast variations of the magnetic fields in the Sun's atmosphere is the reconnection process.     

RCD箝位正激变换器的分析研究

正激变换器因电路简单而广泛应用于中小功率变换场合。但是它的一个固有缺陷是功率晶体管截止期间变压器必须磁复位，因而需要采用附加的复位电路。本文详细介绍了ＲＣＤ箝位正激变换器的工作原理，给出了ＲＣＤ箝位网络的设计准则和步骤。实验结果证实了理论分析的正确性。     

磁悬挂天平的数字控制技术(磁悬挂天平技术研究之三)

本文研究磁悬挂天平的数字控制技术。在 φ60mm 单分力天平装置上,配置了以8031单片计算机为核心的控制系统,不仅实现了飞行器模型的稳定悬挂,而且在外力作用下模型悬挂点保持不变。反馈控制律的设计分三步进行:首先对电磁铁特性进行补偿,使其阶次降低,简化后续的设计工作;然后采用比例微分控制达到系统的稳定最后在系统稳定的基础上,设计了位置积分环节,使系统在常值外力作用吋,能实现模型的悬挂点不发生偏离。这种三段设计法在实验调试时具有实用意义。文中具体介绍了控制系统的实现技术,包括 PWM 功率放大器,单片机硬件和软件。