大尺度场向电流的控制因素

将ＩＳＥＥ－１和ＩＳＥＥ－２飞般测量的地球内磁层场向电流作为行星际磁场与极区地磁活动水平（由ＡＬ表征）的函数。发现大约７５％的场向电流发生在行星际磁场南向时,其余２５％发生在行星际磁场由南向转到北向的半小时内。而且,发生在ＡＬ〈－１５０ｎＴ的场向电流也大约是７５％。场向电流的强度和密度随行星际磁场南向分量及ＡＬ的负值增加而增大。由此而得出结论,内磁层场向电流的产生主要是由行星际磁场控制的,是太阳风     

Coronal plumes and fine scale structure in high speed solar wind streams

We present a solar wind model which takes into account the possible origin of fast solar wind streams in coronal plumes. We treat coronal holes as being made up of essentially 2 plasma species, denser, warmer coronal plumes embedded in a surrounding less dense and cooler medium. Pressure balance at the coronal base implies a smaller magnetic field within coronal plumes than without. Considering the total coronal hole areal expansion as given, we calculate the relative expansion of plumes and the ambient medium subject to transverse pressure balance as the wind accelerates. The magnetic flux is assumed to be conserved independently both within plumes and the surrounding coronal hole. Magnetic field curvature terms are neglected so the model is essentially one dimensional along the coronal plumes, which are treated as thin flux-tubes. We compare the results from this model with white-light photographs of the solar corona and in-situ measurements of the spaghetti-like fine-structure of high-speed winds.     

磁场强度对日冕定态结构的影响

以二维ＭＨＤ模型及时变方法为基础,内外边界完整的设影特征线边界条件,考察了太阳日冕大气的定态结构随偶极场强度的变化情况。模拟结果表明：随着偶极场强度的增加,磁场对太阳风的约束增强,低纬闭磁场打开程度减少,高纬与低纬区速度差增加,并且在阿尔文马赫数为１的点附近达到最大,速度过度区变陡;随着日心距离增加,低纬区宽度减小,速度过渡区变陡,可定性解释Ｕｌｙｓｓｅｓ飞船的新观测事实。     

地基单站GNSS的电离层VTEC高精度解算方法

利用IGS提供的双频GNSS观测数据,分析了Kalman方法解算电离层垂直总电子含量（Vertical Total Electron Content,VTEC）存在的问题,提出了Kriging-Kalman改进解算方法,并对两种方法解算的电离层VTEC进行分析和比较.结果表明：在低纬地区,当观测卫星数量发生改变时,Kalman方法解算的VTEC存在跳变异常,Kriging-Kalman方法解算的VTEC变化较为平稳,不存在跳变现象.对比分析耀斑期间两种方法解算VTEC的变化,发现Kalman方法解算的VTEC变化明显小于耀斑引起VTEC的增量;Kriging-Kalman方法解算结果与实际变化相一致.表明Kriging-Kalman方法计算精度更高,能够更精确计算耀斑等剧烈异常空间天气活动期间的VTEC及其变化,有利于电离层VTEC日常精确监测、研究和工程应用.     

A note on the relationship between sunspot numbers and active days

We have studied the relationship between three different versions of the sunspot number (Group, International and American Sunspot Number) and the number of active days (i.e., the number of days with spots on the solar disk). We have detected an approximately linear relationship for low solar activity conditions. However, this relationship for the International Sunspot Number is very different to the ones obtained with the other versions of the sunspot number. The discordant values correspond to older observations.     

Design concepts for the first 40 km a key step for the space elevator

The Marine Node for the Space Elevator Infrastructure is the base for all activities to load and unload the cargo and climbers. As the basic design of the space elevator power system is solar power only, the first 40 km is hazardous to operations and demands enclosed packaging of fragile tether climbers. A significant question is: how do we place a full-up tether climber, driven by solar power, above the atmosphere? Two approaches, starting at the Marine Node, allow the tether climber to initiate the climb with solar energy above the atmosphere. The third viable approach is to provide a platform at altitude for initiation of tether climb. These approaches would enable solar power to be the source of energy for climbing. The three approaches are:     

Manned exploration and exploitation of solar system: Passive and active shielding for protecting astronauts from ionizing radiation—A short overview

In deep space manned missions for the exploration and exploitation of celestial bodies of Solar System astronauts are not shielded by the terrestrial magnetic field and must be protected against the action of Solar Cosmic Rays (SCRs) and Galactic Cosmic Rays (GCRs). SCRs are sporadically emitted, and in very rare but possible events, their fluence can be so high to be lethal to a unprotected crew. Their relatively low energy allows us to conceive fully passive shields, also if active systems can somewhat reduce the needed mass penalty. GCRs continuously flow without intensity peaks, and are dangerous to the health and operability of the crew in long duration (>1year) missions. Their very high energy excludes the possible use of passive systems, so that recourse must be made to electromagnetic fields for preventing ionizing particles to reach the habitat where astronauts spend most of their living and working time. A short overview is presented of the many ideas developed in last decades of last century; ideas are mainly based on very intense electrostatic shields, flowing plasma bubbles, or enormous superconducting coil systems for producing high magnetic fields. In the first decade of this century the problem began to be afforded in more realistic scenarios, taking into account the present and foreseeable possibilities of launchers (payload mass, diameter and length of the shroud of the rocket, etc.) and of assembling and/or inflating structures in space. Driving parameters are the volume of the habitat to be protected and the level of mitigation of the radiation dose to be guaranteed to the crew. Superconducting magnet systems based on multi-solenoid complexes or on one huge magnetic torus surrounding the habitat are being evaluated for defining the needed parameters: masses, mechanical structures for supporting the huge magnetic forces, needed equipments and safety systems. Technological tests are in preparation or planned for improving density of the current, lightness and stability, to increase working temperature of superconducting cables, and for finding light supporting structures and suitable safety architectures, delineating a possible development program for affording this difficult problem.     

Sandwich module prototype progress for space solar power

Space solar power (SSP) has been broadly defined as the collection of solar energy in space and its wireless transmission for use on earth. This approach potentially gives the benefit of provision of baseload power while avoiding the losses due to the day/night cycle and tropospheric effects that are associated with terrestrial solar power. Proponents have contended that the implementation of such systems could offer energy security, environmental, and technological advantages to those who would undertake their development. Among recent implementations commonly proposed for SSP, the modular symmetrical concentrator (MSC) and other modular concepts have received considerable attention. Each employs an array of modules for performing conversion of concentrated sunlight into microwaves or laser beams for transmission to earth. While prototypes of such modules have been designed and developed previously by several groups, none have been subjected to the challenging conditions inherent to the space environment and the possible solar concentration levels in which an array of modules might be required to operate. The research described herein details our team's efforts in the development of photovoltaic arrays, power electronics, microwave conversion electronics, and antennas for microwave-based “sandwich” module prototypes. The implementation status and testing results of the prototypes are reviewed.     

磁悬浮飞轮转子系统的现场动平衡方法

针对磁悬浮飞轮的转子平衡后转动效果不理想、转子平衡过程复杂等问题,提出了一种基于磁轴承系统特性的现场动平衡检测方法。该方法通过考虑电磁力的影响,进行转子系统的整体动平衡,而非转子本身的动平衡。通过分别检测转子平动的最大位移和相位、转子转动的最大位移和相位,分别得到等效力/力偶不平衡质量的大小和相位,实现了整体不平衡量的现场检测和飞轮转子系统的高精度平衡。试验结果表明,该方法能有效提高飞轮转子系统的平衡精度,转子的跳动量、磁轴承的控制电流以及飞轮轮体的振动量显著减小。     

一种用于电磁轴承特性可控的弹性备用轴承

 为了提高电磁轴承备用轴承的性能,基于动力特性可控的径向电涡流阻尼器、弹性支撑以及滚动型或衬套型备用轴承提出了一种动力特性可控的弹性备用轴承新结构。介绍了这种新型备用轴承的结构和工作原理,在不同的转速和转子不平衡量下测量了电磁轴承失效后转子坠落在新型弹性备用轴承上的瞬态响应,分析了新型备用轴承对转子坠落在备用轴承上的瞬态冲击响应的抑制作用。结果表明：这种新型弹性备用轴承不仅具有结构简单、无工作介质、动力特性易于进行控制等特点,而且还能够显著减小电磁轴承失效后转子坠落在备用轴承上的瞬态冲击响应,使转子的振动很快得以衰减,减小了转子对备用轴承的冲击作用,是一种具有良好发展和应用前景的主动电磁轴承备用轴承结构。