Multi-beam sounding ionograms in the polar cap region: Absorption induced by proton precipitations

The simulation of the multi-beam ionograms in the polar cap region, assessing absorption effect is performed. It is reasonable to distinguish among four different mechanisms responsible for absorption: regular absorption due to solar UV illumination, absorption associated with energetic particles precipitation, absorption connected with X-rays flare and additional absorption in Auroral oval area. In this paper the absorption attributed to proton precipitations is envisaged. The computational model of the high-latitude ionosphere with irregularities oriented to application for the high frequency wave propagation problem was elaborated (Zaalov et al., 2005). A number of the quasi-vertical ionograms in the polar cap region were simulated on the basis of this model. A well-known algorithm (Sauer and Wilkinson, 2008) is applied for the absorption effects calculation. The simulated high-latitude ionograms with the absorption effect and the measured ionograms exhibit quite a good resemblance. This paper illustrates the importance of the understanding and taking into account the absorption effect in the presence of the various structural features in the polar ionosphere (in particular, patches of enhanced electron density) in interpreting ionosonde data.     

SuperDARN cross polar cap potential dependence on the solar wind conditions and comparisons with models

In this study SuperDARN Cross Polar Cap Potentials (CPCPs), collected over the year 2000, are investigated with a goal to statistically assess its relationship with various parameters of the solar wind and Interplanetary Magnetic Field (IMF). We show that SuperDARN CPCPs tend to cluster around discrete values, prescribed by the statistical model, unless the amount of points on each convection map is above ∼300. By selecting CPCP data obtained with radar coverage of >300 points, we investigate the CPCP relationship with IMF B_z and B_y, IMF clock angle, solar wind speed and dynamic pressure, Alfven velocity, Alfven–Mach number, and interplanetary electric field. Some reported tendencies, such as dependence upon IMF B_z, were found to be consistent with measurements by other instruments. We demonstrate that SuperDARN CPCPs show consistency with several theories/empirical models (predicting the CPCP) in terms of a linear trend but, on average, the slopes of the dependencies are at least two times smaller. We also determine the coupling function, out of those published in literature, best correlating with SuperDARN CPCPs.     

High-resolution, coupled thermosphere–ionosphere models for space weather applications

Current first-principles global models of the coupled thermosphere–ionosphere (T–I) system use grids that are too coarse to simulate the mesoscale and small-scale structures that occur in this complex system. These small-scale and mesoscale structures have a great effect on global-scale neutral and plasma distributions and have important consequences for daily space weather. In this paper, we present a new first-principles, high-resolution, T–I nested grid (TING) polar cap model that incorporates multiple nesting levels and two-way interaction. The TING model simulation of the electron densities and temperatures demonstrates the importance of high spatial resolution. It is found that both the mid-latitude electron density trough and its associated dawn electron temperature peak are more pronounced and structured in the nested grid than in the coarse grid. Using the TING model to simulate ionospheric F₂ region electron density variations with geomagnetic activity and universal time (UT) is also discussed.     

带帽单桩力学性状研究

基于弹性理论和假定荷载传递函数形式。对带帽单桩桩土相互作用进行线性分析。根据文献的思路和方法。推导出沉降、竖向应力、侧摩阻力等与荷载水平、深度之间的控制微分方程。采用微分方程的近似解法,得到了相应的解析表达式。直接利用试桩成果的桩顶荷载沉降笑系作为已知条件进行求解,所得结果能够反映带帽单桩桩土相互作用力学性状的一般规律。     

CT5ATP在GTCP131-9BAPU管理中的作用

针对波音737NG机型GTCP131—9B辅助动力装置（APU）出现涡轮叶片移位的故障,分析了叶片移位对APU的影响,提出7CT5ATP方法．并结合南航的经验将其应用于GTCP131—9BAPU的管理中．确定了以CT5ATP作为启动值,结合修后使用时间（TSR）、孔探结论和后中心体盖裂纹检查作为完整性能监控的手段,为APU拆换提供了可信的实践依据,实现7APU单位维修成本的有效降低。     

Solar Wind Control of the Magnetospheric and Auroral Dynamics

A dependence of the polar cap magnetic flux on the interplanetary magnetic field and on the solar wind dynamic pressure is studied. The model calculations of the polar cap and auroral oval magnetic fluxes at the ionospheric level are presented. The obtained functions are based on the paraboloid magnetospheric model calculations. The scaling law for the polar cap diameter changing for different subsolar distances is demonstrated. Quiet conditions are used to compare theoretical results with the UV images of the Earth’s polar region obtained onboard the Polar and IMAGE spacecrafts. The model calculations enable finding not only the average polar cap magnetic flux but also the extreme values of the polar cap and auroral oval magnetic fluxes. These values can be attained in the course of the severe magnetic storm. Spectacular aurora often can be seen at midlatitude during severe magnetic storm. In particularly, the Bastille Day storm of July 15–16, 2000, was a severe magnetic storm when auroral displays were reported at midlatitudes. Enhancement of global magnetospheric current systems (ring current and tail current) and corresponding reconstruction of the magnetospheric structure is a reason for the equatorward displacement of the auroral zone. But at the start of the studied event the contracted polar cap and auroral oval were observed. In this case, the sudden solar wind pressure pulse was associated with a simultaneous northward IMF turning. Such IMF and solar wind pressure behavior is a cause of the observed aurora dynamics.     

A statistical analysis of low frequency geomagnetic field pulsations at two Antarctic geomagnetic observatories in the polar cap region

The aim of this study is to investigate the characteristics of low frequency (∼0.5–5 mHz) geomagnetic field fluctuations as recorded at two Antarctic stations within the polar cap: the Italian observatory Mario Zucchelli Station (TNB) and the French–Italian observatory Dome C (DMC) in order to investigate the spatial extension and propagation characteristics of the phenomena observed at very high latitude. The stations have approximately the same geographic latitude, but a very different corrected geomagnetic latitude, being DMC close to the geomagnetic pole and TNB closer to the auroral oval.     

MY-9易碎材料在武器系统上的应用

介绍了MY-9易碎材料在武器系统上的成功应用。文中以实物和试验数据阐述了MY-9材料的易碎、密封、承压、耐侯和工艺等特性以及在研制导弹发射筒易碎盖和管路密封盖方面的经验。     

正交各向异性多层圆底扁薄球壳在均布载荷作用下的非线性稳定问题

本文导出了正交对称铺层多层圆底扁薄球壳在均布载荷作用下非线性稳定问题的基本方程,用修正迭代法求解,给出了解析表达式,並绘制了载荷-中心挠度曲线,取得了良好的结果,可供工程设计人员参考。     

Multi-instrument observations of large-scale atmospheric gravity waves/traveling ionospheric disturbances associated with enhanced auroral activity over Svalbard

This study reports on observations of large-scale atmospheric gravity waves/traveling ionospheric disturbances (AGWs/TIDs) using Global Positioning System (GPS) total electron content (TEC) and Fabry–Perot Interferometer’s (FPI’s) intensity of oxygen red line emission at 630?nm measurements over Svalbard on the night of 6 January 2014. TEC large-scale TIDs have primary periods ranging between 29 and 65?min and propagate at a mean horizontal velocity of $～$749–761?m/s with azimuth of $～$345–347$°$ (which corresponds to poleward propagation direction). On the other hand, FPI large-scale AGWs have larger periods of $～$42–142?min. These large-scale AGWs/TIDs were linked to enhanced auroral activity identified from co-located all-sky camera and IMAGE magnetometers. Similar periods, speed and poleward propagation were found for the all-sky camera ($～$60–97?min and $～$823?m/s) and the IMAGE magnetometers ($～$32–53?min and $～$708?m/s) observations. Joule heating or/and particle precipitation as a result of auroral energy injection were identified as likely generation mechanisms for these disturbances.