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151.
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The forecast of the terrestrial ring current as a major contributor to the stormtime Dst index and a predictor of geomagnetic storms is of central interest to ‘space weather’ programs. We thus discuss the dynamical
coupling of the solar wind to the Earth's magnetosphere during several geomagnetic storms using our ring current-atmosphere
interactions model and coordinated space-borne data sets. Our model calculates the temporal and spatial evolution of H+, O+, and He+ ion distribution functions considering time-dependent inflow from the magnetotail, adiabatic drifts, and outflow from the
dayside magnetopause. Losses due to charge exchange, Coulomb collisions, and scattering by EMIC waves are included as well.
As initial and boundary conditions we use complementary data sets from spacecraft located at key regions in the inner magnetosphere,
Polar and the geosynchronous LANL satellites. We present recent model simulations of the stormtime ring current energization
due to the enhanced large-scale convection electric field, which show the transition from an asymmetric to a symmetric ring
current during the storm and challenge the standard theories of (a) substorm-driven, and (b) symmetric ring current. Near
minimum Dst there is a factor of ∼ 10 variation in the intensity of the dominant ring current ion specie with magnetic local time, its
energy density reaching maximum in the premidnight to postmidnight region. We find that the O+ content of the ring current increases after interplanetary shocks and reaches largest values near Dst minimum; ∼ 60% of the total ring current energy was carried by O+ during the main phase of the 15 July 2000 storm. The effects of magnetospheric convection and losses due to collisions and
wave-particle interactions on the global ring current energy balance are calculated during different storm phases and intercompared.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
153.
根据国外有关参考资料,对直升机丧尾桨推力导致意想不右偏航进行了讨论分析,简单介绍了直升机飞行时的四种飞行特性,(风标稳定性、尾桨涡环状态、主旋翼桨盘旋涡影响,丧失前飞升力)在意外右偏航中的作用和特点,以及改出方法和实施改出的应急措施,为飞行人员保证飞行安全提供了参考依据。 相似文献
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155.
由稳态飞行确定纵向气动导数 总被引:1,自引:0,他引:1
研究了从稳态对称飞行数据估计气动导数的一种方法,要估计的导数是纵向静稳定性和操纵性导数,尾翼产生的阻尼导数、速度对升力和俯仰力矩系数影响的导数,其方法是基于扩展的纵向静稳定性和操纵性理论以及相应的飞行试验数据表示方法,对于大多数气导数,假设飞行测量数据是以平衡曲线和CL(α)曲线形式给出的,导数估计表达式是由已知常数,直接或非直接测量量的代数关系式构成,估计精度用结果标准误差或系统误差带表示。所研 相似文献
156.
为抑制叶片-盘耦合振动,设计了一种适应整体叶盘结构的环形摩擦阻尼器。拓展了1阶谐波平衡法和整体-局部统一滑动模型在带环形摩擦阻尼器的循环对称结构叶盘减振分析中的应用。使用该方法对实际发动机叶盘在简谐激励下的振动响应进行了仿真计算,结果表明:环形摩擦阻尼器对于某发动机叶盘的0节径4阶危险模态振动有明显抑制作用,且减振效果与阻尼器的质量、安装位置有关,在选定的安装位置最高可使振幅降低75%。在阻尼器结构确定的情况下,利用仿真结果给出了最优的设计方案,包括阻尼器的质量和安装设计。 相似文献
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159.
Jia Luo Han Wang Xiaohua Xu Fangfang Sun 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(10):3088-3101
GPS radio occultation (RO) ionospheric products obtained by Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission during the year of 2014 and the observations from 3 digisonde stations which are located at different latitudes are used to study the influence of different time and space collocation windows on the comparisons of the ionospheric characteristic parameters (ICPs), including the peak density and peak height, derived from the two techniques. The results show that the correlation coefficients (CC) and the standard deviation of the absolute biases (SDAB) between the ICPs derived from the two techniques vary distinctly under different spatial and time collocation windows. Generally, the CC (SDAB) of the ICPs decrease (increase) as the size of the collocation window increases in time dimension or in space dimension. The rate of change of the statistic parameters with the increase in the size of the collocation window in time dimension and space dimension is analyzed for each digisonde station. It is found that within the collocation window of , the influence of the increase of in the space window on the statistical comparison is much more significant than that of the increase of 1?min in the time window, and it is suggested that there can be appropriate relaxation on the time window within the threshold of 60?min to get a balance between the quality of the comparison results and the number of the matched pairs. In addition, it is found that the same variations in the longitude window and in the latitude window may have different influences on the comparison results when the horizontal gradients in electron density are distinctly different along different directions at the digisonde station, and strict space collocation window is preferred when comparing the observations from COSMIC RO with those from the digisonde station in such cases. 相似文献
160.