Outflow of cold dense plasma associated with variation of convection in the outer magnetosphere

Cold dense plasma with the ionospheric origin is often observed in the outer magnetosphere with L values as large as 10. We have examined the electric field data accompanied by the cold dense plasma. The electric field data are obtained by the direct measurement of the drift motion of electrons released from electron guns. We get westward components of convection. In addition, there is an AC component of electric field in the ULF range larger than the DC component. If such a large variation of electric field exists in the vicinity of the stagnation point, the plasmaspheric plasma is expected to flow away to the outer magnetosphere. Then we have a test particle simulation by adding a potential variable in time. There is a particle outflow accompanied by the AC variation of electric field in the ULF range. If there are more complicated variations of electric field, it is possible that particles flow out frequently.     

关于人工源极低频电磁波发射源的讨论——均匀空间交流点电流源的解

大功率人工源极低频电磁波（Control Source of Extremely Low Frequency method, CSELF）技术中,辐射天线由布设在高大地电阻率区的接地长导线源构成,通过接地点向大地注入数百安培的强电流.目前有关强电流在大地中的流动特性和分布规律,尚未完全弄清楚.本文提出一个新思路,将CSELF发射天线分解为两部分:交变的接地长导线源和接地处的交流点电流源,二者响应的叠加构成总场.本文重点讨论了均匀空间下交流点电流源的求解,对比研究了交流点电流源响应、直流点电流源响应之间的差异.结果表明,在小范围内（场源距几十、几百米以内）,均匀空间下交流点电流源场和直流源场差别较小,可相互近似,但在大范围内,交流点电流场比直流场的衰减要快得多.由于CSELF辐射天线跨度上百公里,场源距很大,其电流分布规律遵循交变场规则,不能近似为直流场.     

基于探空火箭的朗缪尔探针方案设计

为研究中国低纬电离层垂直高度的精细结构,研发了一种以探空火箭为平台朗缪尔探针,用于就位测量电离层空间等离子体的特性参数及其扰动情况.本文分析了朗缪尔探针的任务需求和目标,并在朗缪尔探针基本测量原理的基础上,对朗缪尔探针基本测量方案进行了论证分析和设计,包括传感器形状、大小和表面镀层的选取设计,双探针的设计,扫描电压和工作模式的设计,及电子学测量电路的设计.本朗缪尔探针采用两路完全相同的球形探针,两路探针同步工作,各自独立完成测量.朗缪尔探针研制完成后,分别进行了信号模拟源测试和等离子体源测试:信号模拟源测试结果显示两路探针电子学工作状态良好,对微弱电流信号的响应具有很高的线性度;在等离子体模拟装置内对电子探针整机测试的初步结果表明该载荷可以正确测量等离子体的特性参数,能够满足科学探测的需求.     

测震台站智能隔离防雷系统的设计与实现

介绍一种测震台站智能隔离防雷系统的设计实现。其电源部分设计为步进电机控制双电瓶交换充电、放电,保证设备与交流市电完全隔离;信号传输部分设计为通过无线局域网(WLAN)将测震信号传输到网关,再通过有线网络进行数据传输。此设计的优点是使测震核心设备与市电和外线完全物理隔离以达到最好的防雷效果。同时制作先进的NEMS传感器用于检测空间电磁场的变化,根据相应算法判断当地是否发生雷电,在附近有雷电发生时可控制断开信号线、市电等达到保护相关仪器的目的。     

中国电磁监测试验卫星朗缪尔探针数据反演方法研究

朗缪尔探针是目前国际上广泛应用的一种空间等离子体环境就位探测技术.中国电磁监测试验卫星上搭载的朗缪尔探针,是我国首次将探针技术应用于星载平台.本文基于电磁监测试验卫星朗缪尔探针的观测原理及Irving Langmuir等提出的近似理论公式,针对朗缪尔探针的仪器特点,提出了等离子环境下朗缪尔探针观测数据的简化反演方法,并依据朗缪尔探针鉴定件的等离子体罐试验数据对该方法进行了比较验证.结果表明,该数据反演方法的效果较好,可以作为电磁监测试验卫星朗缪尔探针观测数据反演的基本方法,并为后续数据处理提供技术基础.      

Characteristics of low altitude ionospheric electric field over Hainan Island,China

A sounding rocket experiment undertaken by the Chinese Meridian Project from a low latitude station on Hainan Island(19.5°N,109.1°E),China,measured the DC electric field during 05:45-05:52 LT on April 5,2013.The data observed using a set of electric field double probes,as part of the rocket's scientific payload,revealed the special profile of how the vectors of the DC electric field vary with altitude between 130 and 190 km.During the experiment,the vertical electric field was downward,and the maximum vertical electric field was nearly 5.1 mV/m near the altitude of 176 km.The zonal electric field was eastward and slightly less than 0.6 mV/m.The plasma drift velocity was estimated from the E×B motion,and the zonal drift velocity was eastward and of the order of 100 m/s.The zonal wind velocity was also estimated using the drift velocity near the maximum density height in the F1-region,and it was found to be nearly 120 m/s.This work constituted the first in situ measurement of the DC electric field conducted within the Fl-region(between 130 and 190 km) in the East Asian Sector.     

Effect of suprathermal electrons on the intensity and Doppler frequency of electron plasma lines

In an incoherent scattering radar experiment, the spectral measurement of the so-called up- and downshifted electron plasma lines provides information about their intensity and their Doppler frequency. These two spectral lines correspond, in the backscatter geometry, to two Langmuir waves travelling towards and away from the radar. In the daytime ionosphere, the presence of a small percentage of photoelectrons produced by the solar EUV of the total electron population can excite or damp these Langmuir waves above the thermal equilibrium, resulting in an enhancement of the intensity of the lines above the thermal level. The presence of photo-electrons also modifies the dielectric response function of the plasma from the Maxwellian and thus influences the Doppler frequency of the plasma lines. In this paper, we present a high time-resolution plasma-line data set collected on the EISCAT VHF radar. The analysed data are compared with a model that includes the effect of a suprathermal electron population calculated by a transport code. By comparing the intensity of the analysed plasma lines data to our model, we show that two sharp peaks in the electron suprathermal distribution in the energy range 20–30 eV causes an increased Landau damping around 24.25 eV and 26.25 eV. We have identified these two sharp peaks as the effect of the photoionisation of N2 and O by the intense flux of monochromatic HeII radiation of wavelength 30.378 nm (40.812 eV) created in the chromospheric network and coronal holes. Furthermore, we see that what would have been interpreted as a mean Doppler drift veloCity for a Maxwellian plasma is actually a shift of the Doppler frequency of the plasma lines due to suprathermal electrons.     

Electric field variations measured continuously in free air over a conductive thin zone in the tilted Lias-epsilon black shales near Osnabrück,Northwest Germany

Common studies on the static electric field distribution over a conductivity anomaly use the self-potential method. However, this method is time consuming and requires nonpolarizable electrodes to be placed in the ground. Moreover, the information gained by this method is restricted to the horizontal variations of the electric field. To overcome the limitation in the self-potential technique, we conducted a field experiment using a non conventional technique to assess the static electric field over a conductivity anomaly. We use two metallic potential probes arranged on an insulated boom with a separation of 126 cm. When placed into the electric field of the free air, a surface charge will be induced on each probe trying to equalize with the potential of the surrounding atmosphere. The use of a plasma source at both probes facilitated continuous and quicker measurement of the electric field in the air. The present study shows first experimental measurements with a modified potential probe technique (MPP) along a 600-meter-long transect to demonstrate the general feasibility of this method for studying the static electric field distribution over shallow conductivity anomalies.Field measurements were carried out on a test site on top of the Bramsche Massif near Osnabrück (Northwest Germany) to benefit from a variety of available near surface data over an almost vertical conductivity anomaly. High resolution self-potential data served in a numerical analysis to estimate the expected individual components of the electric field vector.During the experiment we found more anomalies in the vertical and horizontal components of the electric field than self-potential anomalies. These contrasting findings are successfully cross-validated with conventional near surface geophysical methods. Among these methods, we used self-potential, radiomagnetotelluric, electric resistivity tomography and induced polarization data to derive 2D conductivity models of the subsurface in order to infer the geometrical properties and the origin of the conductivity anomaly in the survey area. The presented study demonstrates the feasibility of electric field measurements in free air to detect and study near surface conductivity anomalies. Variations in Ez correlate well with the conductivity distribution obtained from resistivity methods. Compared to the self-potential technique, continuously free air measurements of the electric field are more rapid and of better lateral resolution combined with the unique ability to analyze vertical components of the electric field which are of particular importance to detect lateral conductivity contrasts. Mapping Ez in free air is a good tool to precisely map lateral changes of the electric field distribution in areas where SP generation fails. MPP offers interesting application in other geophysical techniques e.g. in time domain electromagnetics, DC and IP.With this method we were able to reveal a ca. 150 m broad zone of enhanced electric field strength.     

Reorientation of three‐component borehole magnetic data

Three‐component borehole magnetics provide important additional information compared to total field or horizontal and vertical measurements. These data can be used for several tasks such as the localization of ferromagnetic objects, the determination of apparent polar wander curves and the computation of the magnetization of rock units. However, the crucial point in three‐component borehole magnetics is the reorientation of the measured data from the tool's frame to the geographic reference frame North, East and Downwards. For this purpose, our tool, the Göttinger Borehole Magnetometer, comprises three orthogonally aligned fibre optic gyros along with three fluxgate sensors. With these sensors, the vector of the magnetic field along with the tool rotation can be recorded continuously during the measurement. Using the high–precision gyro data, we can compute the vector of the magnetic anomaly with respect to the Earth's reference frame. Based on the comparison of several logs measured in the Outokumpu Deep Drill Hole (OKU R2500, Finland), the repeatability of the magnetic field vector is 0.8° in azimuthal direction, 0.08° in inclination and 71 nT in magnitude.     

空基和地基近直流电场观测数据背景特征的相关性

研究空基和地基电磁观测数据各自的特点和规律,并探索两者之间变化的相关性,对将空基和地基观测资料综合应用于地震监测研究具有重要的科学意义.本文利用法国DEMETER卫星的电场观测数据和我国甘肃天祝前兆科学试验台阵红沙湾地震台的水平地电场和垂直地电场、四川省地震局成都地震台的水平地电场的观测资料,重点对卫星和地面探测的近直流频段信号进行了综合分析.研究结果表明:(1)卫星直接观测记录的ULF电场观测值没有呈现明显的年变化趋势,但日侧和夜侧的E_z向(卫星运行速度的切线方向)观测数据呈现了一种长期的周期性特征,与地电场观测资料无相关性和同步性;(2)去掉卫星运行切割磁力线所造成的附加电场后所得的电离层电场与地面记录的地电场数据数量级相当,均集中在10^-1～10^-2 mV/m左右,两者具有可比性;(3)去掉卫星运行切割磁力线所造成的附加电场后,夜侧E_y(卫星轨道平面的法线方向)和E_z(卫星运行速度的切线方向)向的电离层电场数据均具有比较清晰的季节性变化趋势,呈现出较为稳定的年变周期,这与水平地电场的年变趋势一致.电离层电场和水平地电场在数量级和年变趋势上都呈现出明显的一致性.     

Removal of DC power-line magnetic-field effects from airborne total magnetic-field measurements

Power lines carrying DC current can strongly affect total magnetic-field measurements. A simple algorithm using Biot–Savart's law was made to remove magnetic-field components due to a DC power line from airborne total magnetic-field measurements in the Gävle area, Sweden. The power-line location was estimated from observed data and then split into short line segments. The magnetic-field components due to each segment were calculated and summed together to give the total magnetic effect due to the power line at each observation point. The corrected total magnetic field was calculated by subtracting the power-line magnetic-field vector, projected on to the direction of the main field, from the measured total field. The results show a successful removal of the power-line magnetic effect from the total magnetic-field measurements. However, an error in the estimation of the power-line location can result in a magnetic-field residual after correction. A non-linear median filtering was used to remove this residual when needed.     

Polar ionic conductivity profile in fair weather conditions. Terrestrial test of the Huygens/Hasi-PWA instrument aboard the Comas Sola balloon

The permittivity wave and altimetry (PWA) instrument is a part of the CASSINI/HUYGENS HASI experiment and was designed to determine the electrical parameters of the atmosphere of Titan in 2004. In December 1995, a balloon campaign was conducted in León, Spain, to test the HASI onboard hardware and software using a HUYGENS probe mock-up in an electromagnetic-disturbance-free environment (mainly from power emission lines at 50 Hz). This work is concerned with the measurements of small ion polar conductivities and DC fields using the PWA relaxation probes (RP). The two RP electrodes were periodically set to ±5 V relative to the conductive surface of the mock-up and allowed to discharge in the surrounding atmosphere. The polar components of conductivity are calculated from the discharge time, and the DC field from the floating potential differences once the electrodes reach equilibrium. In spite of some observed effects, such as mock-up charging or oscillations in the measurement of potential, the conductivity measurements are coherent and in good agreement with the obtained results in other experiments. The conductivity data were collected in ‘fair-weather’ conditions, up to 30 km during a 4-h flight, every 72 s, giving an altitude resolution better than 400 m. We also discuss the DC field data that do not lead, in presence of charging effects, to a straightforward measurement of the natural DC field. The Comas Solá balloon flight, first real test of the PWA experiment in the terrestrial atmosphere, confirmed the validity of the ionic conductivity measurements but raised the problem of a reliable interpretation of the DC field.     

数字化地震遥测台网不间断供电系统研制

本文介绍一种适用于数字化遥测地震台网的不间断供电系统，它具有交直流不间断切换，输出满足数据采集系统及数据传输设备所需的各种电压要求，并能对备份蓄电池自动恒流、恒压转换充电及过放电保护，冗余量大、可靠性高。解决了无人值守遥测地震台的供电问题。对其它数字设备也有广泛的应用价值。     

2022年1月8日青海门源6.9级地震前电离层异常特征分析

利用张衡一号电磁卫星朗缪尔探针观测的原位电子密度数据和等离子体分析仪观测的原位氧离子密度数据,针对2022年1月8日青海门源M_S6.9地震,分析震前电子密度和氧离子密度异常特征,并总结以往震例。结果显示,在门源M_S6.9地震前11天出现电子密度和氧离子密度高值异常;对电离层异常进行震例统计分析,发现大多数地震前6天以内出现电离层异常,且走滑型地震和逆冲型地震震前居多,讨论异常产生的机理可能为大气声重波机制和电场机制。     

Field Test of the In Situ Permeable Ground Water Flow Sensor

Two in situ permeable flow sensors, recently developed at Sandia National Laboratories, were field tested at the Brazos River Hydrologic Field Site near College Station, Texas. The flow sensors use a thermal perturbation technique to quantify the magnitude and direction of ground water flow in three dimensions. Two aquifer pumping tests lasting eight and 13 days were used to field test the flow sensors. Components of ground water flow as determined from piezometer gradient measurements were compared with ground water flow components derived from the 3-D flow sensors. The changes in velocity magnitude and direction of ground water flow induced by the pump were evaluated using flow sensor data and piezometric analyses. Flow sensor performance closely matched piezometric analysis results. Ground water flow direction (azimuth), as measured by the flow sensors and derived in the piezometric analysis, predicted the position of the pumping well accurately. Ground water flow velocities measured by the flow sensors compared well to velocities derived in the piezometric analysis. A significant delay in flow sensor response to relatively rapid changes in ground water flow was observed. Preliminary tests indicate that the in situ permeable flow sensor provides accurate and timely information on the velocity magnitude and direction of ground water flow.     

Magnetic mapping for the detection and characterization of UXO: Use of multi-sensor fluxgate 3-axis magnetometers and methods of interpretation

Fluxgate vector magnetometers can be powerful instruments in magnetic mapping and in the detection of unexploded ordnance (UXO). Being lightweight and having low power requirements, they allow the development of multi-sensor use. The main problems in using fluxgate magnetometers arise from calibration errors and drift but these can be overcome using a quick and simple method of calibration in the field. This method also has the advantage of compensating permanent and induced magnetic fields generated by magnetized objects carried with the sensors. Measurement accuracy is similar to that obtained with scalar magnetometers. Multi-magnetometer profiling allows direct inversion of raw magnetic data along profiles in order to locate and characterize dipoles typically generated by UXO. The method used is a non-linear inverse procedure that estimates the three coordinates and magnetization vector of the dipole. Application of the technique to both a synthetic case and a field example illustrates the advantages of the method compared with the use of the analytic signal.     

主动空间试验中空间电荷波向电磁波的转换

本文理论分析了电子束沿地磁场穿越均匀、磁化等离子体密度跃变区域时，在弱磁场近似、哨声波激发、低频近似等几种典型情况下电子束流空间电荷波（Space charge wave）向电磁波的转换.先运用小信号假设求得电子束入射进均匀各向异性冷等离子体之后的色散关系和空间电荷波波数，然后借助于电磁波分量和电子束速度的边界条件，求解电子束在等离子浓度发生变化区域激发的波振幅，在几种典型情形下推导出空间电荷波转换为电磁波之间转换系数的近似解，给出了相应波辐射的坡印亭(Poynting)矢量表达式.结果表明，在渡越辐射（Transition radiation）情形下电子束可以在空间等离子体中激发出阿尔芬波（Alfven wave）和哨声波（Whistler wave）.所得结论可用于对主动空间试验结果的分析.     

Observations of flux rope – associated particle bursts with GEOTAIL in the distant tail

Geotail energetic particle, magnetic field data and plasma observations (EPIC, MGF and CPI experiments) have been examined for a number of energetic particle bursts in the distant tail (120Re < |X_GSM| < 130 Re), associated with moving magnetic field structures, following substorm onsets. The features obtained from this data analysis are consistent with the distant magnetotail dynamics determined first by ISEE3 observations and explained in terms of the neutral line model. At the onset of the bursts, before plasma sheet entrance, energetic electrons appear as a field-aligned beam flowing in the tailward direction, followed by anisotro-pic ions. Within the flux rope region, suprathermal ions exhibit a convective anisotropy, which allows determination of the plasma flow velocity, assuming that the anisotropy arises from the Compton-Getting effect. The velocities thus determined in the plasma sheet are estimated to be 200–650 km/s, and compare favourably with the velocities derived from the CPI electron and proton experiment. The estimated length of magnetic field structures varies between 28 and 56 Re and depends on the strength of the westward electrojet intensification. Finally, the three structures reported here show clear magnetic field signatures of flux rope topology. The existence of a strong magnetic field aligned approximately along the Y-axis and centred on the north-to-south excursion of the field, and the bipolar signature in both By and/or Bz components, is consistent with the existence of closed field lines extending from Earth and wrapping around the core of the flux rope structure.