Vertical Component Of Magnetic Field Research Articles

Simulating small-scale dynamo action in cool main-sequence stars

Context. The origin of the ubiquitous small-scale magnetic field observed on the solar surface can be attributed to the presence of a small-scale dynamo (SSD) operating in the sub-surface layers of the Sun. It is expected that a similar process could self-sustain a considerable amount of magnetic energy also in the near-surface layers of cool main-sequence stars other than the Sun. Aims. In this paper the properties of the magnetic field resulting from SSD action operating in the near-surface layers of four cool main-sequence stars and its self-organization into magnetic flux concentrations are investigated numerically. Methods. Three-dimensional radiative magnetohydrodynamic simulations of SSD action in the near-surface layers of four cool main-sequence stars of spectral types K8V, K2V, G2V, and F5V are carried out with the CO5BOLD code. The simulations are set up to have approximately the same Reynolds and magnetic Reynolds numbers, and to disentangle the impact of the effective temperature and the surface gravity on the SSD action from numerical effects. Results. It is found that the SSD growth rates in SI units differ for the four stellar models; the highest and lowest growth rate is for the K2V and F5V model, respectively. This is due to the different turnover times in the four simulations. Even so, the SSD field strengths reached in the saturation phases are similar in all models, with the same amount of kinetic energy converted into magnetic energy. If the magnetic energy that is pumped out from the computational domain across the bottom boundary is partially replenished from outside of the computational domain, we find that the SSD action leads to a sufficient reduction in the convective velocities to reduce the convective horizontal length scales in the convection zone by 5–10%, vanishing towards the optical depth unity level. In this case, strong kilogauss magnetic flux concentrations emerge at the surface, leading to magnetic bright features, which are more numerous and conspicuous for the K2V and G2V models than for the K8V and F5V models. Their vertical magnetic field component on the surface of optical depth unity increases from 1 kG to 1.6 kG with decreasing effective temperature from F5V to K8V. However, more than 90% of the magnetic flux through any of these stellar surfaces has a field strength of less than 1 kG.

Borehole transient electromagnetic response calculation and experimental study in coal mine tunnels

Water damage seriously threatens the safe production of coal mines, so it is necessary to carry out advanced detection to determine the hydrogeological situation, and the preliminary survey often involves the drilling of on-site drill holes in the tunnel. The use of directional drill holes, combined with advanced geophysical prospecting technology, enables advanced water disaster detection with long distance and high precision and is independent of the tunnel environment influence. The transient electromagnetic method (TEM) is highly sensitive to low-resistivity anomalies and plays a crucial role in water damage detection. To address the size limitation of borehole detection, in this study, a small rectangular multi-turn loop borehole advanced detection method was developed (borehole TEM, BTEM) to detect low-resistivity anomalies within 10 m of the borehole in the radial direction. To satisfy the size requirements for borehole detection and the detection distance, a small rectangular multi-turn loop device with a width of 6 cm and a length of 50 cm was designed. To resolve the issue of self-inductance and mutual inductance enhancement caused by multi-turn coils, a uniform full-space low-resistivity abnormal body model was established using the Ansys Maxwell software, and we analyzed the vertical magnetic field component of the rectangular multi-turn small loop at different time points and the transient electromagnetic response of the different turns. Then, we determined the appropriate parameters for the transmitting and receiving device. The developed method was applied to several different experimental scenarios to obtain the electrical distribution of the anomalous body in front of the device, and the measured data were inverted and interpreted to obtain the apparent resistivity-depth profile. The results demonstrate that the inversion results align well with the actual situation, confirming the effectiveness of the BTEM. This research offers a potential solution for borehole advance detection and provides a solid theoretical foundation for further studies.

Vertical stray field measurements using an electron beam in the MEPhIST-0 tokamak

In the MEPhIST-0 tokamak, toroidal magnetic coil system is implemented as a single continuous toroidal solenoid. This design ensures synchronized operation of each segment of the solenoid and requires only one power supply line to operate. However, this configuration has the downside of introducing stray vertical and radial magnetic field components, which result from the inclination of the solenoid segments. Such stray fields can be measured using an electron beam, as previously demonstrated in experiments on T-15, TEXTOR, KSTAR, and SST-1. This paper describes the parameters of the experiment and presents the main results obtained from the MEPhIST-0 tokamak. Two experimental techniques for measuring the vertical magnetic field are discussed: one with a change in the current direction in the toroidal solenoid and one without. The ratio of the stray vertical field to the toroidal field was found to be approximately 0.5%. The conducted experiments highlight the necessity of compensating for the stray vertical field using additional poloidal coils.

The Whole-Space Modeling of the Hazardous Geological Body ahead of the Tunnel Face by the Transient Electromagnetic Method

Karst caves are widely distributed in southwest China, causing difficulties and disasters for tunnel construction. To better detect the krast caves in front of the tunnels under construction using the transient electromagnetic method, in this paper we propose a 3-D finite element method to simulate the multi-parameter transient electromagnetic response of unfavorable geological bodies in a whole-space. First, the models of vertical water-filled faults, water-filled caves and complex geological bodies in front of the tunnel face are established. The horizontal electric field component and the vertical magnetic field component at different time in the whole-space are researched. Secondly, the electromagnetic response features of the caves with different resistivity, buried depths and scales are studied. We found that the resistivity of the target body is 10 times larger than that of the surrounding rocks, and the anomaly amplitude increases obviously with the growing distance from the target body. The deeper the buried depth, the later the anomaly appears and the smaller the anomaly amplitude. The larger the target size, the longer the transient electromagnetic response delay and the larger the anomaly amplitude. We arranged a measuring line on the tunnel face. The full-time apparent resistivity section shows the position and characteristics of the low-resistivity anomalous body, indicating that the transient electromagnetic method (TEM) has obvious advantages in detecting the low-resistivity body in front of the tunnel face. Finally, the TEM is successfully applied to the advanced detection of a karst tunnel to get the electrical distribution of the surrounding rocks in front of the tunnel face. According to the geological conditions of the excavated tunnel, the validity of the TEM in the tunnel advanced prediction is verified.

About 4-Day Rhythm of Proliferative Activity of L-929 Cells in Culture Correlates with the Intensity of Secondary Cosmic Radiation Fluctuations.

The dynamics of proliferative activity of the L-929 cell culture of mouse fibroblast-like cells in the phase of logarithmic growth was compared with some heliogeophysical parameters (Ap and ULF indexes of geomagnetic activity, vertical component of the interplanetary magnetic field, and intensity of fluctuations of secondary cosmic radiation estimated by the neutron monitoring near the Earth's surface). Among the considered heliogeophysical parameters, only the magnitude of fluctuations of minute-to-minute changes in the neutron monitor indicator reliably and negatively correlates with the rate of cell culture reproduction. Considering that the amplitude of secondary cosmic fluctuations is about 5%, which is 0.1% of the total ray flux, and proliferative activity varies in the range of 30-50%, the probability of a direct biotrophic effect of this physical factor is extremely low. It seems likely that proliferative activity of L-929 cell culture is directly affected by another environmental factor, the marker of which is the intensity of neutron counting rate fluctuations.

Improved and Interpretable Solar Flare Predictions With Spatial and Topological Features of the Polarity Inversion Line Masked Magnetograms

AbstractMany current research efforts undertake the solar flare classification task using the Space‐weather HMI Active Region Patch (SHARP) parameters as the predictors. The SHARP parameters are scalar quantities based on spatial average or integration of physical quantities derived from the vector magnetic field, which loses information of the two‐dimensional spatial distribution of the field and related quantities. In this paper, we construct two new sets of spatial features to expand the feature set used for the flare classification task. The first set uses the idea of topological data analysis to summarize the geometric information of the distributions of various SHARP quantities across active regions. The second set utilizes tools coming from spatial statistics to analyze the vertical magnetic field component Br and summarize its spatial variations and clustering patterns. All features are constructed within regions near the polarity inversion lines (PILs) and classification performances using the new features are compared against those using SHARP parameters (also along the PIL). We found that using the new features can improve the skill scores of the flare classification model and new features tend to have higher feature importance, especially the spatial statistics features. This potentially suggests that even using a single magnetic field component, Br, instead of all SHARP parameters, one can still derive strongly predictive features for flare classification.

Characterization of magneto-convection in sunspots

Context. Observations have shown that in stable sunspots, the umbral boundary is outlined by a critical value of the vertical magnetic field component. However, the nature of the distinct magnetoconvection regimes in the umbra and penumbra is still unclear. Aims. We analyse a sunspot simulation in an effort to understand the origin of the convective instabilities giving rise to the penumbral and umbral distinct regimes. Methods. We applied the criterion from Gough & Tayler (1966, MNRAS, 133, 85), accounting for the stabilising effect of the vertical magnetic field, to investigate the convective instabilities in a MURaM sunspot simulation. Results. We find: (1) a highly unstable shallow layer right beneath the surface extending all over the simulation box in which convection is triggered by radiative cooling in the photosphere; (2) a deep umbral core (beneath −5 Mm) stabilised against overturning convection that underlies a region with stable background values permeated by slender instabilities coupled to umbral dots; (3) filamentary instabilities below the penumbra nearly parallel to the surface and undulating instabilities coupled to the penumbra which originate in the deep layers. These deep-rooted instabilities result in the vigorous magneto-convection regime characteristic of the penumbra; (4) convective downdrafts in the granulation, penumbra, and umbra develop at about 2 km s−1, 1 km s−1, and 0.1 km s−1, respectively, indicating that the granular regime of convection is more vigorous than the penumbra convection regime, which, in turn, is more vigorous than the close-to-steady umbra; (5) the GT criterion outlines both the sunspot magnetopause and peripatopause, highlighting the tripartite nature of the sub-photospheric layers of magnetohydrodynamic (MHD) sunspot models; and, finally, (6) the Jurčák criterion is the photospheric counterpart of the GT criterion in deep layers. Conclusions. The GT criterion as a diagnostic tool reveals the tripartite nature of sunspot structure with distinct regimes of magneto-convection in the umbra, penumbra, and granulation operating in realistic MHD simulations.

The magnetic and levitation characteristics of single-grain YBaCuO and GdBaCuO-Ag bulk superconductors in high magnetic fields

In principle, high-temperature superconducting (HTS) flux-pinning maglev has the advantage of self-stable levitation and is therefore a good development prospect as a new rail transit technology. The magnetic field intensity is one of the key factors affecting the levitation performance of single-grain bulk superconductors in the HTS maglev system. To date, however, most researchers have focused on the levitation performance of HTS bulk superconductors in magnetic fields within a permanent magnet guideway (PMG) configuration. The magnitude of the external working magnetic field provided by a PMG is limited to about 0.5 T at 77 K, given that the superconductor usually levitates at a typical working height of 10 mm above the PMG. Therefore, the weak magnetic fields generated by the PMG significantly limits the levitation performance of HTS maglev systems to that of the permanent magnet (PM). In this article, a superconducting magnet test bench was utilized to provide a 0–3 T external magnetic field (B) environment for the study of the levitation force in HTS single grains. The difference in levitation performance between YBaCuO (YBCO) and GdBaCuO-Ag (GdBCO-Ag) bulk superconductors under large, changing magnetic fields was studied systematically. The relationships between levitation force and magnetic field characteristics, including vertical magnetic field component (Bz), transverse magnetic field component (Br), and vertical magnetic field variation (ΔBz) were investigated. The result of variation curves about YBCO and GdBCO bulks' levitation forces under different ΔBz shows that the levitation force of the bulk, single-grain superconductors will reach saturation under a varying ΔBz environment (0.72 and 1.5 T). The values of ΔBz corresponding to the saturation positions are found to be independent of the sizes of the HTS samples. At the same time, GdBCO-Ag exhibits a levitation force that is 112.8% greater than YBCO in B = 3 T magnetic environment. As a result, it is demonstrated that the levitation potential of single-grain HTS bulks can be better exploited by optimizing the distribution of the magnetic field.

Localization of Alternating Magnetic Dipole in the Near-Field Zone with Single-Component Magnetometers

Tri-axis magnetometers are widely used to measure magnetic field in engineering of the magnetic localization technology. However, the magnetic field measurement precision is influenced by the nonorthogonal error of tri-axis magnetometers. A locating model of the alternating magnetic dipole in the near-field zone with single-component magnetometers was proposed in this paper. Using the vertical component of the low-frequency magnetic field acquired by at least six single-component magnetometers, the localization of an alternating magnetic dipole could be attributed to the solution for a class of nonlinear unconstrained optimization problem. In order to calculate the locating information of alternating magnetic dipole, a hybrid algorithm combining the Gauss–Newton algorithm and genetic algorithm was applied. The theoretical simulation and field experiment for the localization of alternating magnetic dipole source were carried out, respectively. The positioning result is stable and reliable, indicating that the locating model has better performance and could meet the requirements of actual positioning.

Buried Magnetic Material Detection System: An SVM Algorithm Application

In recent times, studies about remote-sensing methods have focused on improving variables like sensing distance, sensitivity, and power consumption of available remote-sensing methods. The main target of this study is to improve these variables for the magnetic anomaly detection (MAD) method, in addition to determining upper surface geometry of the sheath with the support vector machine (SVM) algorithm to allow detection of buried ferromagnetic-sheathed explosives, minimize the number of false alarms, and thus shorten the scanning time. The classification process with the SVM algorithm separates this study from others. In line with this, instead of an external magnetic field source, in this study, the Earth's magnetic field was used with a TE100 fluxgate sensor, which has very low power consumption, used as a magnetic sensor to develop a highly sensitive new magnetic measurement and detection system. The system identifies anomalies in the vertical component of the Earth's magnetic field due to the magnetic characteristics of the buried sample in order to determine both the coordinates of the buried object within the scanning field and the upper surface geometry. The system is formed using a five-axis movement CNC platform including sensors and camera. Software was developed using python programming language with a QT graphical user interface (GUI) in order to control the CNC platform, take photographs of the soil, and process sensor data to ensure identification of the upper surface shape of the object under the soil. After obtaining all data for a 30×30 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> scanning area, the software colors the data from blue to red and visualizes this transparently above a photograph of the soil on the monitor. After this stage, a model is created using thresholding, selective search algorithm, and SVM in order to identify the location and upper surface shape of the sample located within the measurement region. Tests performed after SVM training determined the system can classify the upper surface geometry of buried samples with 88% success.

Highly-resolved scanning of magnetic surfaces by FPR integrated on optical fiber

We present a new type of polymer-based Fabry–Perot resonator (FPR) for scanning of the magnetic field distribution with submicrometer resolution. FPR structures were fabricated in a single–step process by three–dimensional (3D) laser lithography based on the direct writing process in polymer IP–Dip and integrated at the end of optical fiber. The key optomechanical part is a thin polymer membrane creating the flexible mirror of FPR with a ferromagnetic microsphere sensitive on a vertical component of magnetic field. For the magnetic field distribution analysis, we used a neodymium magnet composed of microcrystalline grains. The measurement was provided by scanning the FPR probe over the magnetic surface of the neodymium magnet. The interaction of the ferromagnetic microsphere with the magnetic field caused changes of the FPR leading to the spectral changes of reflected light. Detection of dip spectral shift allowed very precise lateral resolution of magnetic induction demonstrated on neodymium magnet surface characterization.

Study on the ULF Magnetic Field Generated by Earth Currents Relating to Large EQs

AbstractULF magnetic anomalies (f &lt; 1 Hz) have been observed prior to multiple large earthquakes (EQs) during the last three decades. A polarization analysis method was produced and applied in many EQ cases in order to discriminate the weak ULF crustal signals from other signals. Although many publications considered the parameter of polarization ratio (amplitude or power ratio of vertical magnetic field component to horizontal components), a key parameter in the polarization analysis method, useful to detect the possible magnetic signals associated with EQs, there were also many doubts on its reliability. The aim of this work is to evaluate the possibilities of the polarization ratio increases prior to large EQs based on the prevail assumption of Earth currents as the source of ULF emissions during the early stage of EQ preparation independent of the mechanism involved in producing the currents, and the parallel 3‐D finite‐difference time‐domain technique is applied to calculate the electromagnetic responses in the whole inhomogeneous Earth‐ionosphere waveguide. The contributions of the lightning discharges on ULF power are also evaluated based on the gridded flash counts included in the Lightning Imaging Sensor climatology data. The results reveal that the surface vertical magnetic field and polarization ratio are possible to increase locally around the epicenters as long as the intensity of the surface seismic magnetic fields are large enough compared with those produced by other sources. Unfortunately, the actual increases are usually difficult to be distinguished obviously mostly due to the weak seismic increases.

Causality and Information Transfer Between the Solar Wind and the Magnetosphere–Ionosphere System

An information-theoretic approach for detecting causality and information transfer is used to identify interactions of solar activity and interplanetary medium conditions with the Earth’s magnetosphere–ionosphere systems. A causal information transfer from the solar wind parameters to geomagnetic indices is detected. The vertical component of the interplanetary magnetic field () influences the auroral electrojet (AE) index with an information transfer delay of 10 min and the geomagnetic disturbances at mid-latitudes measured by the symmetric field in the H component (SYM-H) index with a delay of about 30 min. Using a properly conditioned causality measure, no causal link between AE and SYM-H, or between magnetospheric substorms and magnetic storms can be detected. The observed causal relations can be described as linear time-delayed information transfer.

The PC Index Variations During 23/24 Solar Cycles: Relation to Solar Wind Parameters and Magnetospheric Disturbances

AbstractThe polar cap magnetic activity PC index is regarded as indicator of the solar wind energy that enters into the magnetosphere during the solar wind‐magnetosphere coupling (Resolutions of XXII IAGA Assembly, 2013). This study presents the results of statistical analysis of relationships between the yearly values of PC index and such indicators as the magnetic activity indices (AE and Dst), the solar wind parameters (velocity Vsw, density Nsw, dynamic pressure Pdyn, vertical interplanetary magnetic field (IMF) component Bz, total IMF field |B|, electric field EKL), and the solar activity parameters (sunspot number, coronal mass ejections, stream interaction regions) in course of 23–24 solar cycles. It is shown that the yearly values of the quiet daily curve magnitude (which serves as a level of reference in estimation of the PC index value) changed during 1998–2019 in remarkable agreement with variation of the Solar UV irradiation (150–200 nm) absorbed in the Earth's ionosphere. The yearly values of PC index perfectly correlate with the yearly values of Vsw and |B| and their product electric field EKL, as well as with the yearly values of AE and Dst indices testifying that PC index serves as the ground‐based indicator of the solar wind energy input into the magnetosphere. The yearly values of EKL, PC, AE, Dst correlate with the total IMF field |B| much better that with the IMF Bz component, testifying that efficiency of the solar wind impact on the magnetosphere is defined by the total IMF value, in contrast with Dungey's concept of reconnection.

Reflection of the solar activity Hale cycles on the geomagnetic field secular variations

The effect of dramatic decaying of solar activity in the twentieth cycle on secular variations of the Earth’s geomagnetic field has been investigated. Solar activity decay leads to reduction of the number of magnetic storms on the Earth. During the years of large-scale solar activity negative variations from external sources of the field — circular magnetospheric current, increase, as well as amplitudes of changes of auroral and equatorial ionospheric electrojets. Circular current reduces the horizontal component of the Earth’s magnetic field in low and medium latitudes and increases the vertical component in the high latitudes. In auroral latitudes the intensity of auroral electrojets increases during a magnetic storm. Therefore in more active years average annual absolute values of horizontal component of magnetic field will be smaller at the observatories situated in low and medium latitudes and average annual absolute values of the vertical component of magnetic field will be higher in the high latitudes of the Earth. As far as secular variations are determined as the difference between average annual values of the field, the effect of external sources of the field increases with the growth of solar activity.At the observatories of the northern hemisphere of the Earth (West Europe and North America) decaying of solar activity leads to the increase of average annual values of the field, i.e., to positive secular variations. The effect is maximal in the region of the magnetic pole. The amplitude of the effect decreases with the decrease of the latitude of the observatory. The sign of the effect changes (i.e. negative values of secular variations for the northern hemisphere) at the longitudes 60°Е («Kazan») and 150—160°E («cape Uellen», «Barrov»). Amplitudes of negative secular variations are maximal at the magnetic observatory «Irkutsk». The effect is not observed at the insular observatories as well as the observatories in South America. It is evidently a result of superposition of variations with different signs from the external and internal sources such as variations from the currents in the oceanic flows and the equality by the value of amplitude of secular variations from external and internal sources.

A Portable Magnetometer for Magnetic Measurements of Meter‐Sized Meteorites

AbstractMeteorites contain records of past magnetic fields in the form of natural remanent magnetization (NRM). A key property of meteorite magnetization that provides information about its origin is its dependence on spatial scale. In particular, understanding how the mean remanent magnetization varies from the scale of meteorites to the global scale of their parent bodies would aid in the interpretation of spacecraft magnetometry data. However, the vast majority of meteorite samples whose remanent magnetization have been measured have sizes &lt;10 cm due to the limited size range accommodated by laboratory magnetometers. To address this limitation, we developed a portable magnetometer array that enables remanence measurements of meter‐size meteorites in a non‐magnetically shielded environment. The instrument measures both NRM and induced magnetization using two orthogonal square Helmholtz coil pairs that compensate the vertical and horizontal components of the background magnetic field. An array of four magnetometers mounted on a movable aluminum rail measures the magnetic field at multiple locations around the sample. The instrument is transportable and can be adapted to different sample sizes. After distinguishing the induced component from the remanent component of a sample's total field, the remanence can be estimated from a multipole field inversion combined with nonlinear least squares method. We validated the instrument and data processing on a magnet of known magnetic moment and measured the NRM of a meter‐sized iron meteorite.

Measuring Magnetic Field With Atacama Large Millimeter/Submillimeter Array

This article reviews the use of magnetic bremsstrahlung at short radio wavelengths to measure solar magnetic fields. The vertical component of the chromospheric magnetic field can be deduced from the observed polarization and brightness temperature spectrum at millimeter wavelengths. State-of-the-art 3D radiative magnetohydrodynamic (R-MHD) simulations of the quiet solar atmosphere were used to synthesize observational deliverables at the wavelengths of the Atacama Large Millimeter/Submillimeter Array (ALMA) and to test the applicability of the method. The article provides selected observational examples of the successful application of the method and presents an overview of the recent developments and potential of the magnetic field measurements with ALMA.

Manufacturing, installation, commissioning, and first results with the 3D low-temperature co-fired ceramic high-frequency magnetic sensors on the Tokamak à Configuration Variable.

Innovative high-frequency magnetic sensors have been designed and manufactured in-house for installation on the Tokamak à Configuration Variable (TCV), which are now routinely operational during the TCV experimental campaigns. These sensors combine the Low Temperature Co-fired Ceramic (LTCC) and the classical thick-film technologies and are in various aspects similar to the majority of the in-vessel inductive magnetic sensors foreseen for ITER (around 450 out of the 505 currently being procured are of the LTCC-1D type). The TCV LTCC-3D magnetic sensors provide measurements in the frequency range up to 1 MHz of the perturbations to the wall-aligned toroidal (δBTOR), vertical (δBVER), and radial (δBRAD) magnetic field components. Knowledge of the equilibrium at the last closed flux-surface allows us to then obtain the field-aligned parallel (δBPAR ∼ δBTOR), poloidal (δBPOL), and normal (δBNOR) components, the latter being in most cases rather different from the vertical and radial components, respectively. The main design principles were aimed at increasing the effective area and reducing the self-inductance of the sensor in each of the three measurement axes, which are centered at the same position on each sensor, while reducing the mutual and parasitic coupling between them by optimizing the on-board wiring. The physics requirements are set by the installation of two high-power/high-energy neutral beam injection systems on TCV, i.e., studying fast ions physics, coherent instabilities, and turbulence in the (super-)Alfvénic frequency range. In this paper, we report the manufacturing, installation, and commissioning work for these high-frequency LTCC-3D magnetic sensors and conclude with an overview of illustrative experimental results obtained with this system. The LTCC-3D data provide new insights into the δBPOL coherent (eigenmodes, up to ∼400 kHz) and in-coherent background turbulent fluctuations in the higher frequency range up to ∼1 MHz, which were not previously available with the TCV Mirnov sensors. Furthermore, the LTCC-3D δBPOL measurements allow us to cross-check the data obtained with the standard Mirnov coils and have led to the identification of largeelectromagnetic (EM) noise pick-up for the Mirnov data acquisition (DAQ). When the sources of EM noise pick-up on the Mirnov DAQ are removed, the LTCC-3D data for δBPOL are in good overall agreement, i.e., within the expected measurement uncertainties, with those obtained with the standard Mirnov sensors located at the same poloidal position in the frequency range where the respective data acquisition overlap, routinely up to 125 kHz and up to 250 kHz in some discharges. The LTCC-3D δBPAR measurements (not previously available in TCV or elsewhere) provide evidence that certain instabilities have a finite parallel δB at the wall, hence at the LCFS, consistent with the recent theoretical results for pressure-driven modes. The LTCC-3D δBNOR measurements improve significantly on the corresponding measurements with the saddle loops, which are mounted onto the wall and have a bandwidth of ∼3 kHz (due to the wall penetration time). A detailed end-to-end system modeling tool has been developed and applied to test on the simulated data the actual measurement capabilities of this new diagnostic system and obtain the ensuing estimates of the intrinsic measurement uncertainties. A detailed error analysis is then performed so that, finally, fully calibrated, absolute measurements of the frequency-dependent amplitude and spectral breaks of coherent eigenmodes and in-coherent broadband magnetic fluctuations are provided for the first time in physical units with quantitative uncertainties.

Inductive sounding of layered earth

Research aim. The research results in the development of a technology of continuous multi-frequency induction profiling measuring magnetic field components on long survey routes and detailed elaboration of sections by means of remote induction soundings. Research methodology. Theoretical and experimental studies of magnetic field components change patterns of harmonic vertical magnetic dipole over non-uniform layered earth. Mathematical simulation of harmonic vertical magnetic dipole magnetic field in non-uniform layered earth. Analysis of results. Information value of harmonic vertical magnetic dipole magnetic field components characteristics in low-frequency induction zone has been shown when studying non-uniform geoelectric sections together with the obtained results correspondence to the type of the non-uniform section when carrying out remote inductive sounding. 30 "Izvestiya vysshikh uchebnykh zavedenii. Gornyi zhurnal". No. 4. 2020 ISSN 0536-1028 Scope of results. for extended sections of route research (road and railway, oil and gas pipelines, power transmission lines, etc.) process sequence of vertical magnetic dipole magnetic field characteristics measurement has been determined to determine geoelectric properties of a layered section by means of continuous multi-frequency profiling and determination of homogeneous sections of medium structure with their detailing by discrete analysis by the method of remote inductive sounding.

Dimension Reduction Calculation Method of Toroidal Magnet

For the high temperature superconducting magnetic energy storage (HTS SMES) magnet with large capacity, in order to reduce the leakage magnetic field and the vertical magnetic field component on the wire, it mostly adopts the toroidal magnet structure. However, this structure has imposed new challenges in calculating the AC loss of the magnet. Due to the particularity structure of the toroidal magnet, that is, its magnetic field is not distributed in the 2D axisymmetric manner, it is impossible to calculate the AC loss in the toroidal magnet with a traditional 2D computation model. At the same time, the 3D model has its problems, such as the modeling is complicated; the calculation efficiency is low; the demand for computation is enormous, and so on. In order to provide a solution for calculating the AC loss in the magnet with a non-2D axisymmetric distributed magnetic field, a method of “dimensionality reduction and inversion” is proposed. In this method, the magnetic field distribution in the toroidal magnet is calculated by using a 3D model intended for uniform flow, and the AC loss is calculated by using a 2D model. The practical application shows that this method can provide a solution for calculating the AC loss in the magnet with a non-2D axisymmetric distribute magnetic field, and the calculated results meet the requirements of engineering calculation.