The effects of the solar magnetic polarity and the solar wind velocity on Bz-component of the interplanetary magnetic field

We have studied the effect of both solar magnetic polarity and the solar wind velocity on the Bz-component of the interplanetary magnetic field, IMFBz, for the minimum activity of the solar cycles 21, 22, 23 and 24. We made a statistical study of IMFBz in the first section which is considered as an extension of Lyatsky et al. (2003). They made a statistical study of IMFBz for two periods of minimum solar activity 22 and 23 related to 1985–1987 and 1995–1997 when the solar magnetic field had opposite polarity. Our results seem to be consistent with the results obtained by Lyatsky et al. (2003). We found that there is a dependence of IMFBz on the IMFBx and the solar magnetic polarity for the minimum periods of the selected four solar cycles. In addition, we found that there is a dependence of IMFBz on the solar wind velocity.     

水气动量交换的实验研究

在风浪槽中进行水气动量交换实验，测量了不同风速和风区下的波浪及空气湍流流场。测量数据表明水面上风速分布符合对数律，水气界面附近在小范围的动量交换常通量层。阻力系数ＣＤ随风速增加线性增长，随波龄增加而减小。这一趋向与理论分析及外海帝测结果一致。对风浪发展过程中波浪和空气湍流谱结构的分析证明了水气运动的耦合关系。     

椭球台高杆灯风荷载的实验研究

通过风洞实验研究了多钝体高杆灯在不同水平风向角和竖向风向角下的力与力矩系数。实验结果表明在一定的风向角下，法向阻力系数Cdmax=1.030,法向弯曲力矩系数Cmmax=-0.940,轴向力系数Camax=0.504和Camin=-0．600。     

Solar cycle variation of “killer” electrons at geosynchronous orbit and electron flux correlation with the solar wind parameters and ULF waves intensity

To construct models for hazard prediction from radiation belt particles to satellite electronics, one should know temporal behavior of the particle fluxes. We analyzed 11-year variation in relativistic electron flux (E>2 MeV) at geosynchronous orbit using measurements made by GOES satellites during the 23rd sunspot cycle. As it is believed that electron flux enhancements are connected with the high-speed solar wind streams and ULF or/and VLF activity in the magnetosphere, we studied also solar cycle changes in rank order cross-correlation of the outer radiation belt electron flux with the solar wind speed and both interplanetary and on-ground wave intensity. Data from magnetometers and plasma sensors onboard the spacecraft ACE and WIND, as well as magnetic measurements at two mid-latitude diametrically opposite INTERMAGNET observatories were used. Results obtained show that average value of relativistic electron flux at the decay and minimum phases of solar activity is one order higher than the flux during maximum sunspot activity. Of all solar wind parameters, only solar wind speed variation has significant correlation with changes in relativistic electron flux, taking the lead over the latter by 2 days. Variations in ULF amplitude advance changes in electron flux by 3 days. Results of the above study may be of interest for model makers developing forecast algorithms.     

A Parallel Adaptive 3D MHD Scheme for Modeling Coronal and Solar Wind Plasma Flows

A parallel adaptive mesh refinement (AMR) scheme is described for solving the governing equations of ideal magnetohydrodynamics (MHD) in three space dimensions. This solution algorithm makes use of modern finite-volume numerical methodology to provide a combination of high solution accuracy and computational robustness. Efficient and scalable implementations of the method have been developed for massively parallel computer architectures and high performance achieved. Numerical results are discussed for a simplified model of the initiation and evolution of coronal mass ejections (CMEs) in the inner heliosphere. The results demonstrate the potential of this numerical tool for enhancing our understanding of coronal and solar wind plasma processes. This revised version was published online in June 2006 with corrections to the Cover Date.     

不同型线结构船艏表面压力特性对比实验研究

为优选船艏结构型线方案,在风洞中针对三个在结构型线上仅有细微差别的船艏方案进行表面压力特性对比测试。实验获得了各型线方案模型表面压力空间分布特性和压力脉动特性,并通过表面压力特性的综合对比进行了结构型线评估,为船艏的结构型线设计提供直接的技术依据。     

Self-similar stochastic processes in solar wind turbulence

Solar wind data is used to estimate the autocorrelation function for the stochastic process x(τ) = y(t + τ) − y(t), considered as a function of τ, where y(t) is any one of the quantities B²(t), n_p(t)V²(t), or n_p(t). This process has stationary increments and a variance that increases like a power law τ^2γ where γ is the scaling exponent. For the kinetic energy density and the proton density the scaling exponent is close to the Kolmogorov value γ = 1/3, for the magnetic energy density it is slightly larger. In all three cases, it is shown that the autocorrelation function estimated from the data agrees with the theoretical autocorrelation function for a self-similar stochastic process with stationary increments and finite variance. This is far from proof, but it suggests that these stochastic processes may be self-similar for time scales in the small scale inertial range of the turbulence, that is, from approximately 10 to 10³ s.     

Geomagnetic activity associated with magnetic clouds,magnetic cloud-like structures and interplanetary shocks for the period 1995–2003

Using nine years (1995–2003) of solar wind plasma and magnetic field data, solar sunspot number, and geomagnetic activity data, we investigated the geomagnetic activity associated with magnetic clouds (MCs), magnetic cloud-like structures (MCLs), and interplanetary shock waves. Eighty-two MCs and one hundred and twenty-two MCLs were identified by using solar wind and magnetic field data from the WIND mission, and two hundred and sixty-one interplanetary shocks were identified over the period of 1995–2003 in the vicinity of Earth. It is found that MCs are typically more geoeffective than MCLs or interplanetary shocks. The occurrence frequency of MCs is not well correlated with sunspot number. By contrast, both occurrence frequency of MCLs and sudden storm commencements (SSCs) are well correlated with sunspot number.     

Element Separation in the Chromosphere Ionization-Diffusion Models for the FIP-Effect

Ionization-diffusion mechanisms to understand the first ionization potential (FIP) fractionation as observed in the solar corona and the solar wind are reviewed. The enrichment of the low-FIP elements (<10 eV) compared to the high-FIP elements, seen in e.g. slow and fast wind or polar plumes, is explained. The behaviour of the heavy noble gases becomes understandable. The absolute fractionation, i.e. in relation to hydrogen, can be calculated and fits well to the measurements. The theoretical velocity-dependence of the fractionation will with used to determine the velocities of the solar wind in the chromosphere. This revised version was published online in June 2006 with corrections to the Cover Date.     

Numerical prediction and wind tunnel experiment for a pitching unmanned combat air vehicle

The low-speed flowfield for a generic unmanned combat air vehicle (UCAV) is investigated both experimentally and numerically. A wind tunnel experiment was conducted with the Boeing 1301 UCAV at a variety of angles of attack up to 70 degrees, both statically and with various frequencies of pitch oscillation (0.5, 1.0, and 2.0 Hz). In addition, pitching was performed about three longitudinal locations on the configuration (the nose, 35% MAC, and the tail). Solutions to the unsteady, laminar, compressible Navier–Stokes equations were obtained on an unstructured mesh to match results from the static and dynamic experiments. The computational results are compared with experimental results for both static and pitching cases. Details about the flowfield, including vortex formation and interaction, are shown and discussed, including the non-linear aerodynamic characteristics of the vehicle.