Science China Technological Sciences - Previous studies have shown that EMIC waves occur preferentially in the afternoon sector of the magnetosphere. Here we report obliquely propagating H+ and He+... 相似文献
The nightly mean mesospheric temperature profiles between 80 and 107 km,observed by Na lidar,over Fort Collins,Colorado(41°N,105°W)from 1990 to 2010,are employed to research the temporal and spatial variations and mesopause.We find that the maximum mean temperature is in summer months above 95 km,but reverse below 95 km,and there is a cooler region below 185 K around 97 km in August.The largest seasonal variation is 39.2 K at 81 km,and the minimum is 6.5 K at 96.5 km.The maximum standard derivation in spring and autumn months are larger than other seasons above 105 km,but the temperatures in March,June and September are lower than the other months between 82 km and 100 km where winter is the largest season.Moreover,the seasonal variations of the temperature are about 36,8 and 21 K at 85,95 and 105 km,respectively.winter is colder and summer is warmer above 97.5 km,but reverse below 92 km.The mesopause height is around 102 km in winter,but 84 km in summer,and the mean speed of decreasing or increasing of the mesopause height is about 5 km/month in spring and autumn months which are about 90 km.The lasting time of the mesopause in winter is near 6 months,longer than other seasons,and the mesopause temperature is about 165 K in cool summer,and 185 K in warm winter. 相似文献
Electromagnetic ion cyclotron (EMIC) emission is an efficient mechanism for scattering loss of energetic protons. Here, we report an event that provides both in-situ observation of energetic proton differential fluxes in the inner magnetosphere and precipitation of protons at ionospheric altitudes. During the 7–8 September 2015 geomagnetic storm the Van Allen Probes observed strong EMIC waves around L = 5 and a distinct decrement in fluxes of tens of keV protons around pitch angles 0°–45°. Meanwhile, precipitating protons at ionospheric altitudes were found to significantly enhanced (by several orders of magnitude), measured by NOAA 18 and 19 when they magnetically linked to the Van Allen Probe-A. By solving the Fokker-Planck diffusion equation, we show that EMIC waves can efficiently produce loss of energetic protons within about 2 h in the pitch angle range of ∼ 0°–45°, comparable to the satellite observations.
In this paper, we report two MC events observed by WIND spacecraft with good examples of field-aligned residual flow inside
the MC structure. For both events, the co-moving frames are determined through the deHoffman-Teller (HT) analysis and the
axial orientations are inferred by the newly developed minimal residue (MR) method. The nature coordinate system for both
events are constructed with velocity of the HT frame and the inferred MC axis, the field and flow remaining in the HT frame
are analyzed at this coordinate system. As a result, we find that the residual flows in the co-moving HT frame of the two
MC events are almost anti-parallel to the helical magnetic field. We speculate that the field-aligned residual flows are large
scale coherent hydrodynamic vortices co-moving with the MCs at the supersonic speed near 1 AU. Data analyses show that the
event in slow ambient solar wind is expanding at 1 AU and another one in fast solar wind does not show apparent expansion.
Proton behaviors for both events are quasi-isothermal. Accelerated HT analysis shows that both events have no suitable HT
frame with constant accelerations, which suggests that both events may be moving at the constant speed near 1 AU under the
assumptions of the HT analysis. For both events, the ratio of the dynamic pressure to the magnetic pressure is larger than
that of the thermal pressure to magnetic pressure, which suggests that the dynamic effects due to the plasma flows remaining
in the co-moving HT frame are more important than the thermal effects in the study of MC evolution and propagation.
Supported by the National Natural Science Foundation of China (Grant Nos. 40621003, 40804046, 40536029, 40674084 and 40523006),
the National Basic Research Program of China (“973” Project) (Grant No. 4902006CB806304), the Specialized Research Fund for
State Key Laboratories, and the Open Research Program of the State Key Laboratory of Space Weather, Chinese Academy of Sciences 相似文献
To prepare Carbon/Carbon (C/C) composites with advanced performance, the thermal gradient chemical vapor infiltration (TCVI)
process has been optimized by simulation. A 2D axisymmetric unstable model was built, which included convection, conduction,
diffusion, densification reactions in the pores and the evolution of the porous medium. The multi-physical field coupling
model was solved by finite element method (FEM) and iterative calculation. The time evolution of the fluid, temperature and
preform density field were obtained by the calculation. It is indicated that convection strongly affects the temperature field.
For the preform of carbon/carbon composites infiltrated for 100 h by TCVI, the radial average densities from simulation agrees
well with those from experiment. The model is validated to be reliable and the simulation has capability of forecasting the
process. 相似文献
Science China Technological Sciences - Non-adiabatic behaviour induced by the chorus-electron interaction is an important contributor to the radiation belt dynamics, and largely relies on wave... 相似文献
近年来,从传统中药中寻找活性成分成为研发新药的有效途径,而对中药分子作用机制的研究将显著提高筛选的准确性。本文在前期的研究基础上实现了中药成分的靶标预测、根据预测靶标构建成分-靶标网络、利用网络特征实现分子网络的筛选和分析等核心分析方法,设计了一种高效、易用的中药分子作用网络自动化分析系统。用户可以通过 web 的方式方便的获取中药成分数据,并利用本系统对所需的中药数据进行靶标预测和分子网络研究与分析。 相似文献