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排序方式: 共有4092条查询结果,搜索用时 31 毫秒
1.
Baolin Tan Haisheng Ji Guangli Huang Tuanhui Zhou Qiwu Song Yu Huang 《Solar physics》2006,239(1-2):137-148
Using one-minute cadence vector magnetograms from Big Bear Solar Observatory (BBSO), we analyze the temporal behavior of derived
longitudinal electric currents associated with two flares on July 26, 2002. One of the events is an M1.0 flare which occurred
in active region NOAA 10044, while the other is an M8.7 flare in the adjacent region 10039. Rapid changes of magnetic fields
in the form of flux emergence are found to be associated with both of these events. However, the temporal behavior of electric
currents are very different. For the M1.0 flare, the longitudinal electric current density drops rapidly near the flaring
neutral line; while for the M8.7 flare, the current density rapidly increases, confirming the picture of the current-carrying
flux emergence. We offer a possible explanation for such a difference: magnetic reconnection at different heights for the
two events, near the photosphere for the M1.0 flare, and higher up for the M8.7 flare. 相似文献
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γ射线暴的研究进展(Ⅳ:特强γ射线暴和软γ重复暴 总被引:2,自引:0,他引:2
最近CGRO上的仪器观测到了两个迄今为止发现的最强的λ暴GB930131和GB940217,其光子最高能量均达GeV量级;GB930131的峰值计数率达2×10~6个光子s~(-1);而GB940217的持续时间竟长达90min。另外沉寂了多年的软重复暴源SGR1900 14和SGR1806-20的再次爆发也由BATSE发现。一系列的观测还发现这些软重复暴均与X射线源对应且与超新星遗迹成协。文中对特强暴和软重暴(SGR)的性质及研究进展作了较为详细的评述。 相似文献
4.
V. Majerník 《Astrophysics and Space Science》1996,240(1):133-139
Using the heuristic arguments of quantum physics we describe a new mechanism of the creation of short-living particles from the virtual ones in a stationary gravitation field. The mass of these particles is a function of the intensity of gravitation field. We suppose that the particles created in the gravitation field form a part of the non-baryonic dark matter. Having the intensity of gravitation field in a galaxy we can calculate the density of dark matter created in it by the vacuum quantum fluctuation. We calculate the distribution of this dark matter in a model galaxy and show that its total mass is comparable with the visible mass of the galaxy. 相似文献
5.
A new species,Clathrocorys gracilis nov. spec. of Tripocyrtidae (Radiolarians: Nassellaria) from surface water in northern South China Sea, is described in this
paper. The new species has four radial beams arising from the cephalic base centre, each foot with cup-shaped structure and
ramified bar in the proximal section (near cephalic base), and each wing with a large mesh in the middle, a medium mesh and
a small mesh on each side respectively.
Project supported by the NSFC (No. 40276044) and the Chinese Academy of Sciences (No. KSCX2-SW-101B). 相似文献
6.
Hui-Rong Ji Qi-Jun Pu Yi-Hua Yan Yu-Ying Liu Zhi-Jun Chen Cheng-Ming Tan Cong-Ling Cheng De-Bang Lao Shu-Ke Li Zhi-Qiang Wang Min-Hong Yu Jian-Nong Liu Li-Kang Zhang Ji-Yong Gao National Astronomical Observatories Chinese Academy of Sciences Beijing Hebei Semiconductor Research Institute Shijiazhuang 《中国天文和天体物理学报》2005,5(4):433-441
An improved Solar Radio Spectrometer working at 1.10-2.06 GHz with much improved spectral and temporal resolution, has been accomplished by the National Astronomical Observatories and Hebei Semiconductor Research Institute, based on an old spectrometer at 1-2 GHz. The new spectrometer has a spectral resolution of 4 MHz and a temporal resolution of 5ms, with an instantaneous detectable range from 0.02 to 10 times of the quiet Sun flux. It can measure both left and right circular polarization with an accuracy of 10% in degree of polarization. Some results of preliminary observations that could not be recorded by the old spectrometer at 1-2 GHz are presented. 相似文献
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The paper presents a simple approximate analytical solution of the remote stresses that cause the collapse of a borehole or other circular cylindrical cavity in an infinite elastic space. Regions of parallel equidistant splitting cracks are assumed to form on the sides of the cavity. Their boundary is assumed to be an ellipse of a growing horizontal axis, the other axis remaining equal to the borehole diameter. The slabs of rock between the splitting cracks are assumed to buckle as slender columns, and their post-critical stress is considered as the residual stress in the cracked rock. The buckling of these slab columns is assumed to be resisted not only by their elastic bending stiffness but also shear stresses produced on rough crack faces by relative shear displacements. The energy release from the infinite medium caused by the growth of the elliptical cracking region is evaluated according to Eschelby's theorem. This release is set equal to the energy dissipated by the formation of all the splitting cracks, which is calculated under the assumption of constant fracture energy. This yields the collapse stress as a function of the elastic moduli, fracture energy, ratio of the remote principal stresses, crack shear resistance characteristic and borehole diameter. The collapse stress as a function of crack spacing is found to have a minimum, and the correct crack spacing is determined from this minimum. For small enough diameters, the crack spacing increases as the (4/5)-power of the borehole diameter, while for large enough diameters a constant spacing is approached. In contrast to plastic solutions, the breakout stress exhibits a size effect, such that for small enough diameters the breakout stress decreases as the (? 2/5)-power of the borehole diameter, while for large enough diameters a constant limiting value is approached. Finally, some numerical estimates are given and the validity of various simplifying assumptions made is discussed. 相似文献