共查询到20条相似文献,搜索用时 15 毫秒
1.
The S-302 experiment has benefited more than most from the non-geostationary nature of the GEOS-1 orbit in so far as additional regions of quite different thermal and suprathermal plasmas were made accessible. Electron and positive ion spectra from three regions, the plasmasphere, plasmatrough and boundary layer, are described in order to highlight the variety of thermal plasmas observed.We show how, even in the presence of the local photoelectron sheath and its associated electric potential, the thermal characteristics can be derived. The success of this technique during active periods is demonstrated by the observation of both a heating of the thermal population and the appearance of a second field aligned thermal component during a period of intense wave activity.The detailed structure of the boundary layer adjacent to the magnetopause as observed on the 2nd December, 1977 shows only slow systematic development over a period of more than an hour. Where the thermal plasma density peaks the suprathermal positive ions show considerable drift motion as well as non-Maxwellian characteristics. This region is identified from the thermal particle data as being very close to the magnetopause, however, whether in fact the magnetopause was crossed requires corroborative data from the magnetometer and other experiments. 相似文献
2.
H. Borg L. -A. Holmgren B. Hultovist F. Cambou H. Rème A. Bahnsen G. Kremser 《Space Science Reviews》1978,22(5):511-535
Some preliminary new results are presented of the keV plasma experiment on GEOS-1. Electrons and ions have been observed to stream along the magnetic field lines in the dayside magnetosphere from the ionospheric side of the satellite towards the equatorial plane during magnetic storms, with streaming velocities corresponding to a kinetic energy of the order of a keV. The opposite streaming velocity has also been seen, but primarily in the ions only and with a smaller flux ratio for the two opposite directions along the field lines. The transition between the two opposite streaming directions, as seen by the satellite, has been found to occur even in a fraction of a second.In magnetic storm conditions azimuthal asymmetries in ion fluxes corresponding to electric field intensities of several tens of millivolts per meter have been observed. 相似文献
3.
The relaxation sounder uses the characteristics of the propagation of radiowaves to sound the plasma surrounding the spacecraft. It determines, in particular, the plasma frequency, which gives the electron density.We have now measurements over the whole dayside of the magnetosphere, from the evening to the night sectors.The behaviour of the plasma resonance depends on local time, the nightime echoes being generally weaker.Density measurements thus obtained are shown and discussed in the context of what is presently known about the plasma distribution in the magnetosphere. In particular, the density around apogee is studied as a function of magnetic activity. On the dayside, it appears to vary between a few and a few tens of electrons per cubic centimeter. The evolution of the density profile for several consecutive days is studied and interpreted tracing back the drift of the particles. 相似文献
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P. J. Christiansen M. P. Gough G. Martelli J. J. Bloch N. Cornilleau J. Etcheto R. Gendrin C. Beghin P. Decreau D. Jones 《Space Science Reviews》1978,22(4):383-400
In this paper we describe and discuss the occurrence of natural wave emissions detected by GEOS-1 at frequencies above the electron gyrofrequency. The bulk of the data presented comes from the first six months of satellite operation and thus concerns mainly dayside phenomena. The paper is arranged as follows:After some general remarks, a classification of the wave phenomena is developed in Section 2, and experimental evidence and morphological information relevant to this classification are contained in Section 3. Section 4 includes some preliminary comments on nightside observations. The results are discussed in Section 5, where it is argued that they can be understood as manifestations of electron cyclotron harmonic (Bernstein) wave emission in a plasma parameter range which has only very recently received any theoretical examinations. This theme is further developed in a comparison paper (Ronnmark et al., 1978). 相似文献
6.
A. Pedersen R. Grard K. Knott D. Jones A. Gonpalone U. Fahleson 《Space Science Reviews》1978,22(4):333-346
Quasi-static electric fields have been measured with two spherical probes supported by cable booms providing a baseline of 42 m for the measurement. The performance of the experiment is outlined to demonstrate that electric fields can be measured with accuracies of ±0.7 mV m-1 and ±1.0 mV m-1 in the dawn-dusk and satellite-sun directions respectively. These uncertainties can be considerably reduced under favourable plasma conditions. Examples of typical observations are described.
- The average electric field is always characterized by an irregular structure with time scales 0.5–5 min and with amplitudes of a few mV m-1.
- During substorms dawn-dusk electric fields up to 20–30 mV m-1 have been observed over intervals of 30–60 s.
- Oscillating electric fields with peak-to-peak amplitudes up to 10 mV m-1 and periods of 3–10 min have been observed following magnetospheric disturbances.
7.
Energetic ion measurements of GEOS-1 and ATS-6 are analysed for the period of geomagnetic activity following the arrival of a solar wind shock at 0027 UT on July 29, 1977. GEOS crossed the magnetopause at 6.9 R
E and 0027 UT (1312 LT). Although the difference in local time to ATS at 6.6 R
E is only 2 h ATS seems to remain well inside the magnetopause. During the second orbital pass on this day GEOS crossed the geostationary orbit at the onset time of a major substorm developing at 1120 UT. At this time the local time difference of GEOS and ATS was 12 h. The considerably different energy dispersions are discussed. An azimuthal anisotropy of approximately 20% observed in the GEOS data is interpreted to be the result of a particle density gradient.NOAA-SEL, Boulder, Colo., U.S.A. 相似文献
8.
刷式密封摩擦生热温度场数值计算及试验 总被引:3,自引:2,他引:1
在摩擦热热源条件下建立了CFD多孔介质数值计算模型,对某型航空发动机刷式密封摩擦生热温度场进行计算分析,开展了刷式密封装置全工况条件下摩擦生热试验研究,采用红外成像技术实现了刷式密封动态温度场实时监测。根据试验结果对摩擦生热温度场计算方法进行了修正,引入了刚度修正系数,并对刚度修正系数进行了确定及验证。总结出经过试验验证的航空发动机刷式密封摩擦生热温度场计算分析及试验方法,结果表明:与全工况试验结果相比,计算误差值从48.15%减少到10.67%。 相似文献
9.
Gold R.E. Krimigis S.M. Hawkins S.E. Haggerty D.K. Lohr D.A. Fiore E. Armstrong T.P. Holland G. Lanzerotti L.J. 《Space Science Reviews》1998,86(1-4):541-562
The Electron, Proton, and Alpha Monitor (EPAM) is designed to make measurements of ions and electrons over a broad range of
energy and intensity. Through five separate solid-state detector telescopes oriented so as to provide nearly full coverage
of the unit-sphere, EPAM can uniquely distinguish ions (Ei≳50 keV) and electrons (Ee≳40 keV) providing the context for the
measurements of the high sensitivity instruments on ACE. Using a ΔE×E telescope, the instrument can determine ion elemental
abundances (E≳0.5 MeV nucl−1). The large angular coverage and high time resolution will serve to alert the other instruments
on ACE of interesting anisotropic events. The experiment is controlled by a microprocessor-based data system, and the entire
instrument has been reconfigured from the HI-SCALE instrument on the Ulysses spacecraft. Inflight calibration is achieved
using a variety of radioactive sources mounted on the reclosable telescope covers. Besides the coarse (8 channel) ion and
(4 channel) electron energy spectra, the instrument is also capable of providing energy spectra with 32 logarithmically spaced
channels using a pulse-height-analyzer. The instrument, along with its mounting bracket and radiators weighs 11.8 kg and uses
about 4.0 W of power. To demonstrate some of the capabilities of the instrument, some initial performance data are included
from a solar energetic particle event in November 1997.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
10.
M. López-Puertas B. Funke T. Von Clarmann H. Fischer G. P. Stiller 《Space Science Reviews》2006,125(1-4):403-416
The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board ENVISAT, provided global (pole-to-pole, the
polar night winter regions) measurements of nearly all constituents of the NOy family (including NO, NO2, HNO3 and H2O5) from July 2002 to the end of March 2004 from the upper stratosphere up to the middle mesosphere. The inter-annual variability
of the NO2 and HNO3 abundances in the Arctic and Antarctic winters from September 2002 through March 2004 was enormous with tremendous hemispheric
asymmetry and extraordinary values in two winters. The origin of these variations and of the extreme measured values has been
analyzed on the basis of the changing atmospheric dynamics (using the CH4 tracer) and solar activity, including the extraordinary solar protons events of Oct–Nov 2003. 相似文献
11.
Pauluhn A. Solanki S.K. Schühle U. Wilhelm K. Lang J. Thompson W.T. Rüedi I. Hollandt J. Huber M.C.E. 《Space Science Reviews》2001,97(1-4):63-66
Space Science Reviews - Since the beginning of the SOHO (Solar and Heliospheric Observatory) mission an intercalibration programme was carried out which included simultaneous observations of the... 相似文献
12.
We are discussing methods of stereoscopic 3D reconstruction of coronal loops structures. In our most sophisticated method
we fit loops observed with SOHO/EIT to a set of shape parameters including the internal twist of the loops field lines. We
define this twist as the number of turns of the field line around a torus axis between the footpoints of the loops. Twist
numbers of the order 0–2 are observed. We observe the emergence of an Active Region with twisted loops which detwist as they
expand. The same correlation between detwisting and expansion is observed with filaments in relation to CME formations. On
longer time scale, loops seem to accumulate twist, perhaps due to differential rotation. Rapid losses of twist temporarily
correlate with flares. From our analysis, we expect that the internal twist of coronal structures will play an important role
for the space weather forecast.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
水力脉冲射流特性室内实验和数值模拟 总被引:2,自引:0,他引:2
水力脉冲射流是提高深井机械钻速的一种经济有效的方法,在分析水力脉冲空化射流发生器调制脉冲射流机理的基础上,采用室内实验和数值模拟两种方法对水力脉冲空化射流发生器所产生的脉冲射流特性进行了研究。着重研究了入口流量和叶轮叶片结构对该工具产生的脉动压力振幅的影响。室内实验和数值模拟结果表明:在同一叶轮结构下,随着入口流量的增大,脉动压力振幅呈增大趋势。在同一排量下,采用3叶片叶轮结构的工具调制出脉冲射流的脉动压力振幅较大。因此建议在现场试验条件允许的情况下尽可能地增大泵的排量,并且重点对3叶片叶轮结构的工具进行现场试验研究。 相似文献
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某坦克电台采用螺旋天线以缩短天线的几何尺寸,提高安全性。由于该天线的输入阻抗随频率而变化,需要用一个宽带变负载阻抗匹配网络来实现天线与电台之间的匹配。首先从理论上分析论证了实现具有最平坦频率特性的变负载阻抗匹配网络的可能性。然后,根据实际要求进行了计算机辅助工程设计,并给出了相应的设计和仿真结果。 相似文献
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5月下旬,61岁的波音公司董事长、总裁兼首席执行官詹姆斯·迈克纳尼先生到华访问。他此行的主要目的是慰问员工,拜访中国政府部门的官员,与合作伙伴会面及向外界介绍新任波音中国总裁马爱伦(Bertrand-Marc Allen)先生。用迈克纳尼先生自己的话说,这是一次"常规的访问"。26日,迈克纳尼先生接受了媒体记者的采访。 相似文献
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燃油温度对离心喷嘴雾化特性影响的试验 总被引:2,自引:2,他引:0
对某中心分级燃烧室头部的三种型号离心喷嘴副油路燃油喷入静止大气中的雾化特性进行了试验研究,获得了不同进口燃油温度(-40~80 ℃)和供油压差对燃油雾化特性的影响规律。利用相位多普勒粒子测量技术(PDPA)测量了沿流向距离离心喷嘴出口30 mm平面上的油雾特性,并利用激光粒度分析仪对试验结果进行了进一步验证。研究结果表明:①离心喷嘴的流量数随燃油温度的升高而逐渐减少,且在低温段下降幅度更大;②测量平面上沿直径各处的Sauter平均直径(SMD)在低温段随燃油温度的升高而减小,且油锥中心处的SMD下降幅度更大;③利用激光粒度分析仪测得的油雾场粒径分布在一定程度上验证了PDPA测量结果的正确性,液滴特征直径和液滴尺寸分布系数随供油压差的增大而减小。 相似文献