Comparison of mesopause region meteor radar winds,medium frequency radar winds and low frequency drifts over Germany

During 2004 and 2005 measurements of mesospheric/lower thermospheric (80–100 km) winds have been carried out in Germany using three different ground-based systems, namely a meteor radar (36.2 MHz) at the Collm Observatory (51.3°N, 13°E), a MF radar (3.18 MHz) at Juliusruh (54.6°N, 13.4°E) and the LF D1 measurements using a transmitter (177 kHz) at Zehlendorf near Berlin and receivers at Collm with the reflection point at 52.1°N, 13.2°E. This provides the possibility of comparing the results of different radar systems in nearly the same measuring volume. Meteor radar winds are generally stronger than the winds observed by MF and especially by LF radars. This difference is small near 80 km but increases with height. The difference between meteor radar and medium frequency radar winds is larger during winter than during summer, which might indicate an indirect influence of gravity waves on spaced antenna measurements.     

Determination of an instantaneous Laplace plane for Mercury’s rotation

Mercury is the target of two space missions: MESSENGER, which carried out its first and second flybys of Mercury on January 14, 2008 and October 6, 2008, and the ESA/JAXA space mission BepiColombo, scheduled to arrive at Mercury in 2020. The preparation of these missions requires a good knowledge of the rotation of Mercury.     

关于对喷水室热工计算公式的分析及修正

通过分析喷水室内水和空气之间的热质交换过程，指出目前采用的热工计算公式的不足，并在此基础上推导出喷水室热平衡方程新公式，对理论教学起到一定的指导作用。     

叉流管－管型换热器二维温度场的数值分析

建立并导出叉流管－管型换热器传热过程的二维数学模型及相应的差分格式。对比实验数据和性能计算结果，表明数值方法是有效可行的，据此编制的计算机程序已成功地用于组合发动机空气预冷换热器工作过程的预测。     

某型卫星测试转台俯仰翻转丝杠动力学分析

以某型卫星测试转台俯仰机构为研究对象,在ADAMS中建立了虚拟样机,得到了在翻转过程中丝杠轴向力曲线,并将仿真结果与理论计算结果及试验结果进行比较,验证了虚拟样机建模的合理性;研究结果为同类物理样机设计中滚珠丝杠的选用校核,台体框架的设计校核以及机电联合仿真提供有利数据支撑。     

Dynamics and Composition of Rings

Planetary rings are found around all four giant planets of our solar system. These collisional and highly flattened disks exhibit a whole wealth of physical processes involving dust grains up to meter-sized boulders. These processes, together with ring composition, can help understand better the formation and evolution of proto-satellite and proto-planetary disks in the early solar system. The present chapter reviews some fundamental aspects of ring dynamics and composition. The forthcoming exploration of the Saturn system by the Cassini mission will bring both high resolution and time-dependent information on Saturn’s rings.     

PC-index fluctuations and intermittency of the magnetospheric dynamics

One minute resolution Polar Cap (PC) index was used for the analysis of magnetospheric dynamics. The 1995–2000 time series analysis revealed that the power spectrum of the PC-index fluctuations is a power law in a wide range of frequencies. However, the obtained exponents differ for low and high frequency regions. The probability distribution functions of the PC-index fluctuations show a strong non-gaussian shape, depending on the time of increment. This indicates that the PC-index exhibits intermittency, previously detected in solar wind and auroral electrojet index fluctuations. The PC-index probability distribution functions were fitted by the functional form proposed by Castaing et al. [Velocity probability density functions of high Reynolds number turbulence. Physica D. 46, 177–200, 1990] to describe intermittency phenomena in ordinary turbulent fluid flows. The agreement between the fitting parameters obtained for the PC index and those reported before for solar wind magnetic field fluctuations is within 30%; which is noticeably less than the difference between the same parameters of solar wind and the AE-index fluctuations. This fact indicates that the PC index reflects the solar wind influence on the high-latitude magnetosphere, especially during the summer.     

Modeling Multifractality of the Solar Wind

The question of multifractality is of great importance because it allows us to investigate interplanetary hydromagnetic turbulence. The multifractal spectrum has been investigated with Voyager (magnetic field) data in the outer heliosphere and with Helios (plasma) data in the inner heliosphere. We use the Grassberger and Procaccia method that allows calculation of the generalized dimensions of the solar wind attractor in the phase space directly from the cleaned experimental signal. We analyze time series of plasma parameters of the low-speed streams of the solar wind measured in situ by Helios in the inner heliosphere. The resulting spectrum of dimensions shows a multifractal structure of the solar wind attractor. In order to quantify that multifractality, we use a simple analytical model of the dynamical system. Namely, we consider the generalized self-similar baker’s map with two parameters describing uniform compression and natural invariant measure on the attractor of the system. The action of this map exhibits stretching and folding properties leading to sensitive dependence on initial conditions. The obtained solar wind singularity spectrum is consistent with that for the multifractal measure on the weighted baker’s map.     

A Thermodynamic Approach to the Magnetospheric Complexity: The Role of Fluctuations

Recent studies evidenced that the magnetotail dynamics looks like the one of an avalanching system. This fact has been related with a near criticality dynamics and modelled by singular diffusion and transport equations. Here, we discuss some features of the Earth’s magnetotail dynamics using a thermodynamic approach. In detail we discuss the role played by fluctuations in singular diffusion and relaxation processes from a non-equilibrium thermodynamics point of view. Moreover, the emergence of non-Gaussian statistics is discussed in the framework of the thermodynamics of composite systems.