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81.
A.N. Petrov O.R. GrigoryanM.I. Panasyuk 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(8):1269-1273
The results of proton energy (tens keV – several MeV) spectrum measurements near geomagnetic equator (L < 1.15) at low altitudes (<1000 km) are presented. We used data of experiments onboard ACTIVE, SAMPEX, NOAA TIROS-N satellites and SPRUT-VI (MIR station) and cover a time range of about 30 years (including previous measurements). It was found that the kappa-distribution function fits the experimental spectrum with the best correlation coefficient. A comparison of energy spectra of near-equatorial protons and ring-current protons was made. Using the estimation of the life time of near-equatorial protons we explain the difference in spectral indices of radiation belt and near-equatorial proton formation. We conclude that the ring current is the main source of the near-equatorial protons. 相似文献
82.
M.G.G.T. Taylor B. Lavraud C.P. Escoubet S.E. Milan K. Nykyri M.W. Dunlop J.A. Davies R.H.W. Friedel H. Frey Y.V. Bogdanova A. Åsnes H. Laakso P. Trávnı´cek A. Masson H. Opgenoorth C. Vallat A.N. Fazakerley A.D. Lahiff C.J. Owen F. Pitout Z. Pu C. Shen Q.G. Zong H. Rème J. Scudder T.L. Zhang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(10):1619-1629
During conditions of northward interplanetary magnetic field (IMF), the near-tail plasma sheet is known to become denser and cooler, and is described as the cold-dense plasma sheet (CDPS). While its source is likely the solar wind, the prominent penetration mechanisms are less clear. The two main candidates are solar wind direct capture via double high-latitude reconnection on the dayside and Kelvin–Helmholtz/diffusive processes at the flank magnetopause. This paper presents a case study on the formation of the CDPS utilizing a wide variety of space- and ground-based observations, but primarily from the Double Star and Polar spacecraft on December 5th, 2004. The pertinent observations can be summarized as follows: TC-1 observes quasi-periodic (∼2 min period) cold-dense boundary layer (compared to a hot-tenuous plasma sheet) signatures interspersed with magnetosheath plasma at the dusk flank magnetopause near the dawn-dusk terminator. Analysis of this region suggests the boundary to be Kelvin–Helmholtz unstable and that plasma transport is ongoing across the boundary. At the same time, IMAGE spacecraft and ground based SuperDARN measurements provide evidence of high-latitude reconnection in both hemispheres. The Polar spacecraft, located in the southern hemisphere afternoon sector, sunward of TC-1, observes a persistent boundary layer with no obvious signature of boundary waves. The plasma is of a similar appearance to that observed by TC-1 inside the boundary layer further down the dusk flank, and by TC-2 in the near-Earth magnetotail. We present comparisons of electron phase space distributions between the spacecraft. Although the dayside boundary layer at Polar is most likely formed via double high-altitude reconnection, and is somewhat comparable to the flank boundary layer at Double Star, some differences argue in favour of additional transport that augment solar wind plasma entry into the tail regions. 相似文献
83.
Michael A. Raadu 《Space Science Reviews》1994,68(1-4):29-38
A Double layer (DL) in a current carrying plasma sustains a localised net potential difference and acts as an impedance converting electrical energy to directed particle energy determined by the DL potential. DL's accelerate equal numbers of ions and electrons for relativistic energies, otherwise electron energisation predominates. Their time independent structure may be described as a BGK (Bernstein-Greene-Kruskal) state analogous to that for laminar shocks, and certain existence criteria must be satisfied. The generalised Langmuir criterion requires total particle pressure balance over the DL and may imply propagation in the plasma reference frame. The Bohm criteria require sufficiently large current densities and are closely related to the local stability condition at the edges of the DL. The DL potential must be sustained externally, for example by the release of stored magnetic energy. A steady state is also possible where (externally maintained) mass motions drive a dynamo region connected by currents to the DL which acts as an electrical load. 相似文献
84.
Pair creation in relativistic double layers in shown to have consequences for the charge density in the double layer and the current flowing through it. 相似文献
85.
86.
分析了碳单元的结构特征,推论出双基和改性双基推进剂的分解温度、表面温度不随压力和初温而改变,以及碳单元顶端温度相对稳定.依此讨论了燃速温度系数及其规律. 相似文献
87.
88.
建立了平面四杆机构连杆曲线的结点与原动件的角位移的六次方程式 ,对连杆曲线结点的类型、存在条件及识别方法进行了研究 ,提出了以曲线的结点、回转数、变曲点、曲率极大点等为基准的连杆曲线的综合法 ,验证了几何特征值用于解决复杂曲线综合问题的快速有效性。 相似文献
89.
In the past two years, many progresses have been made in magnetospheric physics by using the data of Double Star Program, Cluster, THEMIS and RBSP missions, or by computer simulations. This paper briefly reviews these works based on papers selected from the 126 publications from March 2012 to March 2014. The subjects cover various sub-branches of magnetospheric physics,including geomagnetic storm, magnetospheric substorm and magnetic reconnection. 相似文献
90.
轻合金双激光束双侧同步焊接(Double Laser-Beam Bilateral Synchronous Welding,DLBSW)技术是一项极具应用前景与发展潜力的先进技术,对实现航空航天壁板结构的轻量化与高效率制造具有重要意义。然而,由于轻合金本身的材料特性与DLBSW技术的特殊性,轻合金T型结构DLBSW技术仍然存在诸多细节问题有待深入探索。分析了轻合金T型结构DLBSW技术的焊接冶金特点与稳定性,重点研究了DLBSW接头中焊接缺陷的形成机理与抑制措施,考察了T型接头的力学性能与断裂机理。此外,探讨了轻合金T型结构DLBSW过程数值模拟研究的重要意义。 相似文献