Induction Vector Research Articles

3-D inversion of MT data from the Sabalan geothermal field, Ardabil, Iran

Since the true Earth is 3-D in nature, a three-dimensional (3-D) inversion has clear advantages over lower dimensional inversions. We utilized a 3-D magnetotelluric (MT) inversion code, WSINV3DMT, to obtain a realistic resistivity model using a long period MT data set collected in the Northwest Sabalan geothermal field in Ardabil, Iran. The apparent resistivity and phase curves, the magnetic induction vectors, the impedance polar diagrams and the rotational invariant of impedance tensor, indicate a complex 3-D conductivity structure. After setting up the model parameters and designing the appropriate block discretization, we performed the 3-D inversions for two sets of observed data; one set includes the full MT impedance tensor and another set contains only off-diagonal elements of the MT impedance. The final model was selected according to the relative magnitude of the data misfit and the model norm with respect to various Lagrangian multipliers. The results of this study illustrate the 3-D inversion of the off-diagonal elements of MT impedance tensor is precisely enough to explain the structures related to the geothermal source. The obtained results were compared with the results of available 2-D models and they are then interpreted using all of the geological and drilling data of the area. The main outcome of this study is the precise delineation of the geometry of geothermal source that is located at the center of the study area with a surface coverage of about 7 km 2 . • Sabalan geothermal system in Iran is known to have very complex geology. • We apply 3-D MT inversion in this area. • This geothermal field is well detected and delineated by 3-D inversion results.

Multipole models of the geomagnetic field: Construction of the Nth approximation

The fact that the geomagnetic potential, as well as magnetic induction and its gradient, can be represented with an arbitrary accuracy in the scope of multipole models has been justified programmatically and analytically. The obtained expressions are brief and can be utilized in analytical and computer-based studies using methods of computer algebra and numerical computations. Previously unknown analytical expressions for the components of the first seven multipole tensors, expressed in terms of the Gaussian coefficients, have been obtained for applied problems of space dynamics. An algorithm that makes it possible to construct analytical expressions for the arbitrary-order multipole tensor and magnetic induction vector components in any finite approximation has been developed.

Variations of the induction vector in Japan

Variations of the induction vector in Japan

Performance analysis of the Faraday magnetic field point scanner

PurposeThe purpose of this paper is to discuss results of laboratory tests performed on a point type Faraday magnetic field scanner device designed for monitoring applications.Design/methodology/approachAutomated laboratory setup using a reference magnetic induction source was used to test key parameters such as spatial resolution and signal to noise ratio.FindingsVolume scans of magnitude of the magnetic field induction vector prove applicability of the sensor and demonstrate its advantages.Practical implicationsSensor is applicable for safe and accurate scanning of the magnetic induction spatial distribution.Originality/valueThe paper presents a novel test setup.

Precise centering and field characterization of magnetic quadrupole lenses

A setup to investigate fields of magnetic quadrupole lenses was designed and constructed. It allows the spatial position of the axis and the multipole structure of the field of a lens (or lenses) with aperture sizes from 11mm to be determined. The technique employed is based on the measurements of the radial component of the magnetic induction vector using a Hall probe at the points located on the three dimensional surface with subsequent data processing using the Laplace equation. The article presents design and performance characteristics of the setup as well as results from the accuracy evaluations in the measurements of the centers and parasitic multipole field components of the magnetic quadrupole lenses in the integrated doublet.

Annual and diurnal variations of induction vectors in relation to geodynamic processes

Recent results provide evidence for the existence of variations in induction vectors associated with geodynamic processes. Earthquakes (EQs) and volcanic eruption precursors have an aperiodic temporal regime and appear once or several times prior to their occurrence. The regular periodic variations of induction vector are also observed, and they are a new interesting geophysical phenomenon. These periodic variations must be considered as a background while looking for precursory signals associated with EQs and volcanic activities. Detailed discussion on the periodic variations of induction vectors is presented in the paper. Annual and diurnal variations obtained from the processing of synchronous data of three observatories in Southeastern Europe – Surlari, Nyzhnie Selysche and Dymer – are discussed for identifying precursory information.

Polarization sounding of the pulsar magnetosphere

AbstractThe possibility of a polarization sounding of the pulsar magnetosphere is examined, using intrinsic pulsar emission as a probe signal, for modern radio telescopes operating in the meter and decameter wavelength range. Different models of the pulsar magnetosphere at altitudes higher than a radius of critical polarization are used. The propagation medium besides magnetosphere is described by the stratified model, in which each layer has its own density of free electrons and vector of magnetic induction, as well as the spatial and temporal fluctuation scales of these parameters.The frequency dependence of the polarization parameters of the pulsar radio emission, obtained in the broad band for a selected pulse phase, will enable a sounding deep into the pulsar magnetosphere.

Variability of averaged annual impedances of the Earth and their spatial gradients in Europe

Secular variations of the Earth’s impedance for periods from several hours till month have been detected by two kinds of induction sounding methods. The analysis is based on the dynamic spectra of the 30-70 year data series observed at eight geomagnetic observatories in Central Europe. The apparent resistivities obtained by the generalized magnetovariation sounding method have been averaged for annual intensity taking into account coherence values. These annual variations are correlated with the intensity of the Sun activity. Besides, the Earth’s apparent resistivities have some quasi-linear trends. Five groups of observatories have been analyzed to estimate the lateral gradients of response functions. The most brightly changes of the induction vectors have been established for imaginary arrow C v near the years 1969-1972. The obtained results have been used to estimate possible variability of the Earth’s conductance. The peculiarities of this phenomenon are discussed.

Simulation of the Magnetic Induction Vector of a Magnetic Core to be Used in FFC NMR Relaxometry

This paper is a contribution for the assessment and comparison of magnet properties based on magnetic field characteristics particularly concerning the magnetic induction uniformity in the air gaps. For this aim, a solver was developed and implemented to determine the magnetic field of a magnetic core to be used in Fast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) relaxometry. The electromagnetic field computation is based on a 2D finite-element method (FEM) using both the scalar and the vector potential formulation. Results for the magnetic field lines and the magnetic induction vector in the air gap are presented. The target magnetic induction is 0.2 T, which is a typical requirement of the FFC NMR technique, which can be achieved with a magnetic core based on permanent magnets or coils. In addition, this application requires high magnetic induction uniformity. To achieve this goal, a solution including superconducting pieces is analyzed. Results are compared with a different FEM program.

Splines in the approximation of geomagnetic fields and their transforms at the Earth’s surface

SUMMARY Infinite 2-D splines of separated variables are a convenient tool to be used for approximation over a rectangle at the Earth’s surface of geomagnetic field components and transfer functions obtained from measurement data in unevenly distributed nodes. The spline approximation derived in this manner makes it possible to numerically calculate 2-D Hilbert transforms and hence to reconstruct the magnetic tensor from tippers (induction vectors) by solving a large system of linear equations. The proposed method was tested on synthetic data and applied to the Carpathian region with the use of archival induction vectors collection.

High-speed CMOS magnetic angle sensor based on miniaturized circular vertical Hall devices

We present a high-speed CMOS integrated magnetic angle sensor consisting of two 8-contact circular vertical Hall devices (CVHD). The biasing and sensing of the Hall voltage is rotated clockwise for the first device, and counter clockwise for the second one. The output voltages of the two devices are processed separately in two channels and they act as a reference signal one to another. The output of the sensor is a pulse width modulated signal whose width is proportional to twice the angle enclosed between the in-plane magnetic induction vector and the reference axis. The information on the angle is directly present in the pulse width modulated signal without the need for either arctg function implementation or complicated angle detection algorithms. The sensor's concept together with optimized interface and signal conditioning electronics allows for very high bandwidth. The measurement range of the sensor is 0–90°, with possibility for further extension. The sensor achieves tracking the angle of the in-plane magnetic vector oscillating at up to 200kHz (12,000,000rpm), or equivalently, having an angular speed of 628,000rad/s. To our knowledge, this is the highest bandwidth of a completely CMOS integrated magnetic angle sensor. The maximum absolute error for these speeds is ±4° without any calibration, the response time is 1μs, and the angular resolution is 0.5°.

Теоретические основы для определения магнитной проницаемости металла труб, используемых при нефтедобыче

Background Pipeline transportation of oil and gas fluids is widely used in the system of recovery, collection and transport of well flowstream in oil industry. In some cases long operating pipes are used (old fund). Accounting that effective and ecologically safe operating of such pipes requires the periodic control system. The electromagnetic methods are widely used as pipe inner diagnostics. So that magnetic permeability determination basing on electromagnetic field measuring is an important scientific and practical problem. It is necessary to calculate the magnetic permeability in spite of specific electric conduction as it is known from the pulse borehole crack and thickness detector operating experience. Realization of this project needs non-grounded spherical contour with the direct current as a source of magnetic field. Electric permeability does not influence the magnetic field of such source, thus, pipe becomes a paramagnetic characterized by magnetic permeability and geometrical parameters. Theoretical basis of such approach is a set of algorithms and calculating formulas, allowing the calculation of magnetic induction vector components (direct problem) and accurate determination of magnetic permability. Aims and Objectives To consider the ability of accurate determination of magnetic permeability and to derive all necessary formulas. Results The work deals with the basic theory of numerical evaluation of the ability to determine the magnetic permeability. There was developed the examples of its practical application using the axial component of magnetic induction vector. This theoretical basis allows to specify the results of interpretation of borehole crack detector, and could be used as a basis for investigation of oil product pipeline facilities.

Direct observation of dynamics of single spinning dust grains in weakly magnetized complex plasma

The rotational dynamics of single dust grains in a weak magnetic field is investigated on a kinetic level. Experiments reveal spin-up of spherical dust grains and alignment of their magnetic moments parallel to the magnetic induction vector. The angular velocity of spinning prolate grains varies as magnetic induction increases to 250 G. Spinning dust grains are found to flip over only when the magnetic field magnitude is changing. The results demonstrate that dusty plasma has paramagnetic properties. Qualitative interpretations are proposed to explain newly discovered phenomena.

Self Magnetic Field and Current-loop of Electron with Five Different Radii and Intrinsic Properties

With the rotation of charge in a circular path current-loop is generated. This results in the production of magnetic fields in a charged body. This self (internal) magnetic field is treated here with five different radii of electron. Closed loop line integral of magnetic induction vector or the integral form of the Ampere's circuital law is expressed in terms intrinsic properties of electron.

Conductivity distribution beneath Lascar volcano (Northern Chile) and the Puna, inferred from magnetotelluric data

During two field campaigns in 2007 and 2010, long-period and broadband magnetotelluric measurements were conducted in the Central Andes of northern Chile and northwestern Argentina at a latitude of 23.7°S. The study area spans from the Precordillera over the active volcanic arc of the Western Cordillera until the western part of the Puna. A special focus was on Lascar, a subduction related stratovolcano with an historical activity characterized by fumarolic emissions and occasional sub-plinian eruptions, like the one occurred on 1993. The broadband instruments, covering a period range between T=0.005s and 1000s, were installed in the proximities of Lascar volcano, while the long-period devices (T=10s–10,000s) were installed on a profile slightly south of Lascar, crossing the Salar de Atacama basin, the volcanic arc and reaching the western border of the Puna.Remote reference and robust techniques were used for data processing. Induction vectors, phase tensor ellipses and strike direction of the conductivity distribution were calculated, showing some 3-D behavior for the Lascar sites at shallower depths, with induction vectors close to the edifice influenced partially by the topography. 3-D modeling and inversion revealed conductive anomalies beneath Lascar volcano, but also beneath the Puntas Negras volcanic chain. For the long-period transect, the behavior is closer to a 2-D case, with more stable strike direction coherent with induction vectors and phase tensor ellipses. The major result of 2-D inversion is a vast high-conductivity zone in the backarc crust, which seems to be the southern extension of a large highly conductive anomaly observed in prior studies beneath the Altiplano.

Magnetic inspection of fatigue degradation of a high-carbon pearlitic steel

The effect of high-cycle fatigue loading of U10 steel specimens with a fine-lamellar pearlite structure that were a annealed for a short time on the character of variations of the tangential component of the magnetic induction vector of specimens in a residual-magnetization state has been studied. It was found that fatigue loading up to major fatigue-crack formation leads to an increase in the tangential component of the magnetic induction vector and to nonuniformity of the magnetic induction distribution along the length of a specimen. This is due to the spheroidization of cementite plates, which occurs in U10 steel specimens under a fatigue load. Major fatigue-crack formation is accompanied by the appearance of a clearly pronounced peak in the distribution of the tangential component of the magnetic induction vector. The magnetic measurement technique that was used allows us to record both structural changes and cracks that result from the fatigue degradation of high-carbon-pearlitic steel.

Rotational Magnetization in Transformer Cores—A Review

Usually, rotational magnetization (RM) is associated with rotating machine cores. However, in more restricted ways, it also arises in three-phase transformer cores. Modern designs of T-joint yield detours of flux, as a source of RM in the T-joint, the middle limb ends, as well as in the yokes. Simulation of RM is possible by means of so-called rotational single sheet testers which should consider the large grains of highly grain oriented materials. Their high effective anisotropy yields induction patterns of rhombic or lancet-like type with maximum values of axis ratio a up to 0.5, and very high angular velocity round the materials hard directions. Compared to elliptic RM-as arising in non-oriented materials-the corresponding losses are lower due to restricted induction in the hard direction. But they show strong increase with (i) rising a and (ii) rising angular velocity of the induction vector. The magnetostrictive strain shows a pronounced (negative) maximum in the rolling direction with values up to 10 ppm, the transverse direction and normal direction exhibiting positive maxima of lower extent. With respect to industrial relevance, significant RM effects are restricted to the vicinities of T-joints. They represent the location of maximum core loss and also of maximum magnetostrictive strain as a source of audible core noise.

Deep resistivity cross section of the intraplate Atlas Mountains (NW Africa): New evidence of anomalous mantle and related Quaternary volcanism

The Atlas Mountains are characterized by high elevations and Quaternary volcanism. Long period magnetotelluric data acquired along a NNW‐SSE transect reveal the presence of a conductive anomalous mantle below the High Atlas. Data dimensionality analyses show a preferent N80°E strike of the deep resistivity structure in agreement with the induction vector alignment at long periods. Accordingly, a 2D inversion of the data set was carried out. Large resistive bodies at the crustal basement most likely correspond to batholiths emplaced in more conductive metapelites. They are covered by outcropping conductive sedimentary detritic and carbonate rocks. Lithospheric thinning producing anomalous mantle and basin development in the Atlas probably started during Triassic‐Jurassic rifting. Inversion tectonics since the Oligocene produced low shortening on previous lithospheric weak zones, with thrusting of the Atlas above the stable African plate. Melting at the top of the anomalous mantle is connected with Quaternary basaltic volcanism in the Middle Atlas.

ГЕОДИНАМІКА

Temporal variations of induction vectors in the Transcarpathian active seismic zone were investigated. Analyses of long-term series of magnetic-variation observations let’s to made a conclusion about correlations of Wise vectors variations with seismic processes in the crust and, also, about perspectives of a method’s implementation in detection of local earthquakes precursors (with M>3 magnitude) in the geological-geophysics conditions of the Transcarpathians trough.

Control over heat exchange and deceleration of a “magnetized” body in a rarefied plasma flow

The rotation of the induction vector of a self-magnetic field with respect to the velocity vector of an incident plasma flux is shown to be an efficient mean for controlling convective heat exchange and the aerodynamic quality of a magnetized dielectric axisymmetric body.