基于磁桥路的钢丝绳LMA型损伤检测试验研究

基于磁桥路检测原理,建立了钢丝绳LMA型损伤等效磁路模型,分析了钢丝绳金属截面积与磁桥路的磁感应强度之间的关系,并推导出了两者的理论方程式;基于霍尔元件的霍尔效应原理,制作了磁桥路的磁感应强度检测器,通过试验,获得了不同钢丝绳金属截面积（即不同损伤）条件下的霍尔检测电压,由此,建立了钢丝绳金属截面积与霍尔检测电压的线性方程式,实现了钢丝绳LMA型损伤的定量检测.     

Solar wind entry via flux tube into magnetosphere observed by Cluster measurements at dayside magnetopause during southward IMF

By analyzing hot ion and electron parameters together with magnetic field measurements from Cluster, an event of magnetopause crossing of the spacecraft has been investigated. At the latitude of about 40° and magnetic local time (MLT) of 13:20 during the southward interplanetary magnetic field (IMF), a transition layer was observed, with the magnetospheric field configuration and cold dense plasma features of the magnetosheath. The particle energy-time spectrograms inside the layer were similar to but still...     

Reconstruction of plasmoid and traveling compression region in the near-Earth magnetotail

Cluster spacecraft observed an earthward flowing plasmoid along with a travelling compression region(TCR)structure in southern plasma sheet boundary layer(PSBL)at 21:09 UT of September 19,2001.We have reconstructed the two-dimensional topology of the magnetic field structure observed by C1 using Grad-Shafranov reconstruction method.Results show that C1passed through part of a plasmoid,which compressed the lobe magnetic field and formed a TCR.The size of the whole plasmoid structure in X direction is estimated to be about 3 RE.Furthermore,using multi-spacecraft observations,we have found some detailed information about this structure.First,C1 observed bi-streaming electron components,which supports our suggestion that the spacecraft passed through closed field lines.Second,a small magnetic field perturbation within this plasmoid accompanied by slight decrease in electron flux suggests that a flux rope core might exist at the center of the plasmoid.     

Key technique of a detection sensor for coal mine wire ropes

Wire ropes, employed extensively in coal mine hoists and transportation systems are subject to damage due to wear,corrosion and fatigue. The extent of damage and the carrying capacity of ropes are closely related to the sense of safety by staff and equipments. Magnetic flux leakage detection method (MFL), as an effective method, is these days widely used in detection of bro-ken strands of wire ropes. In order to improve the accuracy of detection of flaws in wire ropes by magnetic flux leakage (MFL), the effect of the distance between a sensor and the surface of a wire rope (i.e., lift-off) on detection by magnetic flux leakage was in-vestigated. An analysis of the main principles for the choice of lift-off is described by us and a new method that improves the struc-ture of the detector is proposed from the point of view of the design of a magnetic circuit, to restrain the impact of fluctuations of sensor lift-off. The effect of this kind of method is validated by simulation and computation. The results show that the detection sensitivity is markedly increased by this method. Furthermore, the signal-to-noise ratio (SNR) can be increased by over 28%. This method will lend itself to offer reliable scientific information to optimize the structure of excitation devices and improve the accu-racy of MFL detection.     

钢丝绳缺陷检测综合传感器的研究

利用漏磁场原理检测钢丝绳断丝,磁桥回路测量钢丝绳磨损信号,霍尔位移传感器检测钢丝绳直径变化,并实现在一个传感器中对上述诸多缺陷的综合检测．在信号处理方面,结合不同信号特征,设计了相应的电路和处理软件,实现了缺陷的定量检测．     

Microwave diagnostics of magnetic field strengths in solar flaring loops

We have performed microwave diagnostics of the magnetic field strengths in solar flaring loops based on the theory of gyrosynchrotron emission. From Nobeyama Radioheliograph observations of three flare events at 17 and 34 GHz, we obtained the degree of circular polarization and the spectral index of microwave flux density, which were then used to map the magnetic field strengths in post-flare loops. Our results show that the magnetic field strength typically decreases from ∼800 G near the loop footpoints to ∼100 G at a height of 10–25 Mm. Comparison of our results with magnetic field modeling using a flux rope insertion method is also discussed. Our study demonstrates the potential of microwave imaging observations, even at only two frequencies, in diagnosing the coronal magnetic field of flaring regions.

     

Coordinated Cluster/Double Star observations of dayside flux transfer events on 6 April 2004

With the Double Star Program TC1 in the equatorial orbit and Cluster tetrahedron in the high latitude polar orbit, a conjunct observation of FTEs on the dayside magnetopause (MP) on April 6, 2004 is presented in this study. The FTEs observed by TC1 at low latitudes are characterized to be generated in the subsolar region and the obtained flux tube axes orientate along the predicted low latitude component magnetic reconnection X-line, indicating that these FTEs were more likely to be generated through multiple X-line reconnection or single X-line bursty reconnection. During the same period, Cluster also encountered a series of magnetosheath FTEs with their axes pointing roughly along the interplanetary magnetic field. At last, the global FTE configuration is obtained from observations in different locations, which is in good agreement with the “elbow shape” model. Supported by the NSFC (Grant No. 40731056) and the Chinese Key Research Project (Grant No. 2006CB806300)     

Magnetic reconnection structures in the boundary layer of an interplanetary magnetic cloud

An interplanetary magnetic diffusion region was detected by WIND during 0735-0850 UT on May 15, 1997 when the front boundary layer of a magnetic cloud passed through the spacecraft about 190 earth radii upstream of the earth. The main signals of magnetic reconnection processes are: (i) Flow reversal was detected at about 0810 UT. The counter-streaming flows have the speeds of about 65 and 41 km/s, respectively, with an angle of about 140 degree between them. (ii) Hall magnetic field was detected. The Hall fields -By and +By, perpendicular to the X-Z plane, with their magnitude up to -7.0 nT, are superposed upon a guide field about 12 nT. (iii) Alfvenic fluctuations are obviously intensified inside the reconnection region; at the front boundary of the reconnection region, a slow-mode-like discontinuity was detected.(iv) Ions are heated intensively inside the reconnection region, with their temperature three times higher than that ahead of the boundary layer; electrons are also heated, with a little enhan     

Multiple magnetic topologies in flux transfer events: THEMIS measurements

Flux transfer events (FTEs) are local transient magnetic reconnections at the magnetopause (MP) that provide channels for transport of solar wind energy and plasma into the magnetosphere (MSP). All current theoretical models suggest that FTEs are open-flux ropes; however, global simulations show that they contain both open and closed magnetic fields. To clarify this topology, we analyzed 441 events observed by THEMIS and investigated their magnetic topologies. Only one type of open field line was detected in most magnetosheath (MSH) FTEs, independent of the polarity of the B_n bipolar signatures. Newly formed MSH field lines were also observed. In the all MP boundary layers FTEs and most MSP FTEs, multiple types of topologies were observed, irrelevant to the B_n bipolar polarity. Closed field lines were found in all MP boundary layers and MSP FTEs. Meanwhile very few boundary FTEs contained the newly formed MSH flux. In some situations, only closed field lines were seen in MSP FTEs, which are referred to as the fossil FTEs. These results, which largely differ from the traditional view, demonstrate the existence of complex magnetic topologies in FTEs. Based on these results, we propose a new 3D FTE picture to modify the current FTE models.     

Solar wind transport into magnetosphere caused by magnetic reconnection at high latitude magnetopause during northward IMF: Cluster-DSP conjunction observations

An event of Cluster-Double Star conjunction observations of magnetic reconnection at high latitude magnetopause nightside of both cusps and solar wind transport into magnetosphere caused by such reconnection process has been investigated. During northward IMF, Cluster/SC1 observed accelerated flows and ion heating associated with magnetic reconnection at high latitude magnetopause nightside of southern cusp. And Double Star observed cold dense solar wind plasma transported into dayside magnetosphere. The analysis on such conjunction observations shows that: (1) during northward IMF, magnetic reconnection occurs at high latitude nightside of southern cusp, accompanied by accelerated flows that are observed by Cluster/SC1; (2) the direction of the accelerated flows, with its sunward component V _x , dawnward component V _y , northward component V _z , is quite consistent with the theoretical anticipation under the condition of northward IMF with dawnward component B _y ; (3) reconnection can heat plasma more in parallel direction than in perpendicular direction, to a level of about 4 keV; (4) with reconnection taking place at high latitude magnetopause nightside of the southern cusp, TC-1 observed cold and dense plasma transported into magnetosphere; (5) by reconnection at high latitude magnetopause nightside of both cusps, solar wind flux tube can be captured by magnetosphere and pulled into dayside magnetosphere. This event presents further observational evidence for magnetic reconnection at high latitude magnetopause nightside of both cusps as an important mechanism of solar wind transport into magnetosphere. Supported by the Ministry of Science and Technology of China (Grant No. 2006CB806305), the National Natural Science Foundation of China (Grant Nos. 40621003, 40674094), and the Hundred Talents Program of the CAS     

Small interplanetary magnetic flux rope

Small interplanetary magnetic flux ropes (SIMFRs) are often detected by space satellites in the interplanetary space near 1 AU. These ropes can be fitted by a cylindrically symmetric magnetic model. The durations of SIMFRs are usually <12 h, and the diameters of SIMFRs are <0.20 AU and show power law distribution. Most SIMFRs are observed in the typically slow solar wind (<500 km/s), and only several events are observed with high speed (>700 km/s). Some SIMFRs demonstrate abnormal heavy ion compositions, such as abnormally high He abundance, abnormally high average iron ionization, and enhanced O7+ abundance. These SIMFRs originate from remarkably hot coronal origins. Approximately 74.5% SIMFRs exhibit counter-streaming suprathermal electron signatures. Given their flux rope configuration, SIMFRs are potentially more effective for substorms. SIMFRs and magnetic clouds have many similar observational properties but also show some different observations. These similar properties may indicate that SIMFRs are the interplanetary counterparts of small coronal mass ejections. Some direct bodies of evidence have confirmed that several SIMFRs are interplanetary counterparts of CMEs. However, their different properties may imply that some SIMFRs have interplanetary origins. Therefore, one of the main aims of future research on SIMFRs is to determine whether SIMFRs originate from two different sources, that is, some events are formed in the solar coronal atmosphere, whereas others originate from the interplanetary space. Finally, in this paper, we offer some prospects that should be addressed in the future.     

SuperDARN CUTLASS Finland radar observations of high-latitude magnetic reconnections under northward interplanetary magnetic field (IMF) conditions

A number of backscatter power enhancement events with "equatorward-moving radar auroral forms" in the high-latitude ionosphere were observed by SuperDARN CUTLASS Finland radar when the IMF was northward during 09:00 -10:00 UT on 26 March 2004. These events were also associated with sunward flow enhancements at each location in the Northern Hemisphere which were shown in ionospheric convections measured by the SuperDARN radars. These are typical features of high-latitude (lobe) magnetic reconnections. The durations of the velocity enhancements imply that the evolution time of the lobe reconnections is about 8-16 min from their origin at the reconnection site to their addition to the magnetotail lobe again. In additional, the Double Star TC-1 spacecraft was moving from magnetosheath into magnetosphere, and crossing the magnetopause near the subsolar region during this interval, and observed typical low-latitude magnetic reconnection signatures. This infers that the dayside high- and low-latitude reconnections may occur simultaneously.     

Shrinkage of magnetosphere observed by TC-1 satellite during the high-speed solar wind stream

During the interval 06:14–07:30 UT on August 24, 2005, since the Earth’s magnetopause was suddenly compressed by the persistent high-speed solar wind stream with the southward component of the interplanetary magnetic field (IMF), the magnetopause moved inward for about 3.1 R_E. Meanwhile, TC-1 satellite shifted from northern plasma sheet to the northern lobe/mantle region, although it kept inward flying during the interval 06:00–07:30UT. The shift of TC-1 from the plasma sheet to the lobe/mantle is caused by the simultaneous inward displacements of the plasma sheet and near-Earth lobe/mantle region, and their inward movement velocity is larger than the inward motion velocity of TC-1. The joint inward displacements of the magnetopause, the lobe/mantle region and the plasma sheet indicate that the whole magnetosphere shrinks inward due to the magnetospheric compression by the high-speed solar wind stream, and the magnetospheric ions are attached to the magnetic field lines (i.e. ‘frozen’ in magnetic field) and move inward in the shrinking process of magnetosphere. The large shrinkage of magnetosphere indicates that the near-Earth magnetotail compression caused by the strong solar wind dynamic pressure is much larger than its thickening caused by the southward component of the IMF, and the locations of magnetospheric regions with different plasmas vary remarkably with the variation of the solar wind dynamic pressure. Supported by the National Natural Science Foundation of China (Grant Nos. 40604018, 40523006), CSSAR (Grant No. O72114AA4S), Scientific Research Start-up Foundation for President Prize of CAS, 973 Program of China (Grant No. 2006CB806305) and the Specialized Research Fund for State Key Laboratories     

使用两根钢丝绳承载时的安全性能分析

单根钢丝绳的承载安全性能取决于其所受到的载荷及自身的特性,对此已有多项研究［１］。而在钢丝绳实际应用中,通常为多根钢丝绳同时使用。这种情况下的承载安全还取决于载荷在各根钢丝绳中的分布;同时还应考虑当其中一根钢丝绳被拉断时,其余钢丝绳因此受冲击。本文将通过两根相同钢丝绳的承载安全性能分析,即分析当其中一根钢丝绳被拉断时,另一根钢丝绳仍能可能可靠工作的概率,为考虑多根丝绳系统承载安全性能奠定基础。     

Numerical study of asymmetric driven reconnection at dayside magnetopause

A two-dimensional compressible MHD code has been used to numerically study the asymmetric driven reconnection processes in the vicinity of the magnetopause. The initial magnetic field configuration is assumed to be in a mechanical equilibrium state. The cases with identical temperatures ( Tm0/ Ts0 = 1 .0) and four different ratios of magnetic field strength ( Q = Bm0/Bs0 = 1.0, 1.5, 2.0, 2.5), and the case with Tm0/ Ts0 = 2.0 and O = 1.5 are investigated ( Bm0, Tm0 and B, Ts0 are the initial magnetic strength and temperature outside the current sheet on the magnetosphere and the mag-netosheath, respectively ). When the magnetic field on the magnetosheath side is set as southward, a recurrent formation of multiple magnetic bubbles with various scales occurs under the action of the inward plasma flow imposed at the left and right boundaries. In the simulation, some bubbles coalesce into a bigger one and then it is convected out of the simulation domain; the others are convected through the top boundary all     

Adsorption Capacity of Kaolinite for Copper （Ⅱ） under Magnetic Field

The adsorption of Cu^2 on kaolinite under magnetic field was studied at 25℃.The magnetic effects were investigated by designing the variation of exposure time, rnagnetie flux density and the method of magnetic exposure. The results from these study show that the magnetic treatment significaatly enhance the fraction of adsorption of Cu^2 ,the adsorption of Cu^2 by kaolinite increases with the increase of pH value from 2 to 6. Both the magnetic exposure time and the magnetic flux density promote the fruetion of adsorption Cu^2 on kaolinite.     

Statistical study of magnetotail flux ropes near the lunar orbit

Flux-rope/TCR events near the magnetotail lunar orbit(-67R_E GSM X* -39RE) were studied using magnetic-field and plasma data measured by THEMIS B and C between January 2011 and March 2012. The aberrant coordinate GSM*, where the X* axis is rotated 4° relative to GSM-X, was used to count the occurrence rate. The number ratio of earthward to tailward events was about 3:5. Moreover, the event occurrence rate distribution showed a clear dawn-dusk asymmetry distribution, with dusk-side events accounting for 57.98%. A superposed epoch analysis of the flux-rope events showed that earthward events had a shorter duration in the leading than in the trailing part. Earthward events also displayed a lower temperature and a lower flow speed than tailward events. We studied the relationship between the event occurrence rate and geomagnetic activity level even further. The occurrence rate of tailward flux-rope/TCR events increases with increasing AE-index, whereas earthward events occur mainly in the relatively quiet period of geomagnetic activity(AE ~ 100–300 n T). Flux-rope/TCR events identified within a 10 mm time frame were treated as belonging to a single reconnection event. By comparing the occurrence rates of earthward and tailward events along X*, we estimated the most likely location of the near-Earth reconnection site as X* = -36R_E.     

Electron dynamics and wave activities associated with mirror mode structures in the near-Earth magnetotail

We report the observation of mirror mode structures by Cluster spacecraft at around X~-16 RE in the Earth’s magnetotail.The wavelength of the mirror structure is larger than 7000 km,corresponding to tens of ion gyroradii.Features of the mirror structures are similar to those detected in the magnetosheath:the anti-correlation between the magnetic field strength and plasma density,zero phase velocity in the plasma rest frame and linear polarization.The structures were observed in a region bounded by two dipolarizations during a substorm intensification.Thus,the dipolarization process may provide a plasma condition facilitating the growth of the mirror mode structures.Another interesting feature is the electron dynamics within the mirror structures.Thermal electron energy flux has an enhancement at 0°and 180°pitch angles inside the magnetic dips of the first three mirror structures and an enhancement at 90°pitch angle inside the magnetic dip of the last structure.The different electron distribution inside the mirror structures might be a result of different evolution stages of the mirror wave.The last structure may be in the nonlinear stage of the mirror instability,whereas the three others with quasi-sinusoidal waveforms may be in the linear stage.In addition,we found that intense whistler waves were confined within the magnetic dips.We conjecture that whistler waves observed in the first three dips were generated in a remote region,then they were trapped in the mirror mode troughs and transported toward the spacecraft;while the whistler wave detected in the last dip was excited locally by the electron anisotropy instability.     

两种管径比的绕流热柱体旋涡信号比较

在考虑壁面热效应的情况下,当雷诺数为0.6×104~5.0×104,分别对管径比为0.4和0.24两种工况下的柱体尾迹旋涡脱落的流动情况进行实验.结果表明:加热使得旋涡流动发生明显变化,其影响表现在旋涡脱落信号傅里叶变换峰值的改变上;这种影响随雷诺数的变化有一临界值ReL,加热在ReL两侧对旋涡所起作用相反,并且ReL随管径比的不同而不同.通过对不同管径比工况的分析比较,发现同等加热强度下小管径比的壁面热效应对旋涡流动影响更明显.     

The electromagnetic wave experiment for CSES mission: Search coil magnetometer

The seismic activities on the Earth can produce a disturbance of the electromagnetic field and particles in the ionosphere. The search coil magnetometer(SCM) mounted on China Seismo-Electromagnetic satellite(CSES) is designed to measure the magnetic field fluctuation of low frequency electromagnetic waves in the frequency range of 10 Hz–20 k Hz. The SCM comprises a three-axis search coil sensor mounted on a 4.5 m boom and an electronic box inside satellite module. The sampling rate of the SCM is 51.2 k Hz and the time resolution of the power spectrum density(PSD) is 2 s. The frequency resolution is 12.5 Hz.There are three operation modes: survey, detailed survey and calibration. In the survey mode, the SCM can provide a PSD in the whole frequency range of 10 Hz–20 k Hz and wave forms in the low frequency range below 2 k Hz while in the detailed survey mode the SCM can provide both PSD and wave forms in the whole frequency range of 10 Hz–20 k Hz. The sensitivity of the SCM instrument is 5.0×10~(-4) n T Hz~(-1/2) at 10 Hz, 5.0×10~(–5) n T Hz~(-1/2) at 200 Hz, 3.4×10~(-5) n T Hz~(-1/2) at 2 k Hz and 1.1×10~(-4) n T Hz~(-1/2) at 20 k Hz. The telemetry rate is ~0.85 Mbps in the survey mode and ~3.0 Mbps in the detailed survey mode. The phase difference between three axes can be made generally with a precision of less than 1.0°. The dynamic range of the SCM instrument is over 100 d B. The orthogonality of three mechanical axes of search coil senor is better than 0.13°. The performance of SCM can satisfy the requirement of scientific objectives of CSES mission.