Modelling of airborne Full Tensor Magnetic Gradiometry using data from the INFACT project

The measurement of the magnetic field has been a &#8220;backbone&#8221; geophysical method in mineral exploration since the 17th century. The existing instrumentation that measures Total Magnetic field Intensity (TMI) are a routinely used in ground, borehole and airborne surveys. In the TMI intensity data it is possible to observe certain signatures of magnetised objects, but retrieval of both magnetisation intensity and shape of 3-D magnetised objects from TMI can be difficult due to the vector nature of magnetisation and fundamental non-uniqueness of potential fields interpretation. Moreover, the presence of magnetic material in the host rock and/or presence of remanent magnetisation are challenges for TMI data interpretation.Full Tensor Magnetic Gradiometry (FTMG) measurements provide the complete description of the magnetic field and hence an opportunity to get more information on the size, shape and material property of the magnetic rock mass. This is because the signatures in magnetic field originating from a specific magnetic object is observed in all independent components of magnetic field gradient tensor and thus, joint analysis of these tensor components constrains the number of possible magnetic models that fit the same data. In addition, observing the full tensor of magnetic field makes it possible to estimate the remanent magnetization with respect to the induced magnetization field if no a-priori information of remanent magnetization is available.Highly sensitive magnetometers based on SQUID (Superconducting QUantum Interference Devices) technology has been successfully adopted in FTMG airborne measurements during the past decade. This achievement has given magnetic methods a new opportunity in terms of purely magnetic data modelling. In our work the benefits of interpretation of tensor airborne FTMG data are demonstrated through forward modelling and inversion with the grid search multiobjective global optimisation. As a case study, we consider airborne FTMG data measured with Supracon&#174; JESSY STAR system in Northern Finland during the INFACT project.Acknowledgements: This study has been done in the framework of EU Horizon 2020 funded INFACT project (webpage: https://www.infactproject.eu).

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Mitigating remanent magnetization effects in magnetic data using the normalized source strength

Geophysics ◽

10.1190/geo2012-0225.1 ◽

2013 ◽

Vol 78 (3) ◽

pp. J25-J32 ◽

Cited By ~ 40

Author(s):

Mark Pilkington ◽

Majid Beiki

Keyword(s):

Magnetic Field ◽

Remanent Magnetization ◽

Field Data ◽

Magnetic Data ◽

Magnetization Distribution ◽

Source Strength ◽

Inversion Algorithm ◽

Data Set ◽

Magnetic Field Data ◽

The Magnetic Field

We have developed an approach for the interpretation of magnetic field data that can be used when measured anomalies are affected by significant remanent magnetization components. The method deals with remanent effects by using the normalized source strength (NSS), a quantity calculated from the eigenvectors of the magnetic gradient tensor. The NSS is minimally affected by the direction of remanent magnetization present and compares well with other transformations of the magnetic field that are used for the same purpose. It therefore offers a way of inverting magnetic data containing the effects of remanent magnetizations, particularly when these are unknown and are possibly varying within a given data set. We use a standard 3D inversion algorithm to invert NSS data from an area where varying remanence directions are apparent, resulting in a more reliable image of the subsurface magnetization distribution than possible using the observed magnetic field data directly.

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Magnetic vector inversion using XYZ measured by fluxgate magnetometer in UAV

10.5194/egusphere-egu21-13006 ◽

2021 ◽

Author(s):

Arto Karinen

Keyword(s):

Magnetic Field ◽

Remanent Magnetization ◽

Magnetization Vector ◽

Field Direction ◽

Magnetic Data ◽

Total Field ◽

Main Field ◽

Vector Inversion ◽

The Magnetic Field ◽

Measured Magnetic Field

Traditionally, the inversion of magnetic data assumes the magnetization of the local geology to run parallel to the Earth&#8217;s internal magnetic field that is usually modelled using International Geomagnetic Reference Field (IGRF). Assuming the magnetization parallel to the main field, only the total (scalar) magnetic data are the sufficient input for the inversion of source susceptibility.Local magnetization may alter from the main field direction in areas of remanent magnetization. Recently, magnetization vector inversion (MVI) using the total field has become an important tool trying to distinguish magnetic data affected by remanenence. Total field as a scalar field exclude all information of the direction of the internal magnetization and more information is required to reveal any remanent magnetization from the main field direction. &#160;Compared to total field using the 3-component XYZ vector magnetic measurements provide more information of the source.&#160; More measurements increase the unambiguous nature of data and may reveal the areas of possible remanence.&#160;To measure XYZ vector magnetic field we use fluxgate 3-component magnetometer with rigid installation on a fixed-wing UAV. With the help of accurate inertial measurement units the measured magnetic field can be determined in the direction of fixed coordinate system. The components of the measured magnetic field rotated into the geographical coordinate represent the magnetic field at survey area.UAV survey provided the data as the input for the inversions. We made the inversion separately for both susceptibility and magnetization vector. Susceptibility inversion means inversion of induced magnetization, i.e., a single component of magnetization parallel to the main field direction. Magnetization vector inversion, however, resolves all three components of magnetization, which may or may not include remanent magnetization in addition to induced one.The benefits from utilizing XYZ components of the magnetic field with magnetization inversion seem promising in finding remanenence magnetization.&#160;&#160;

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Joint analysis of the magnetic field and Total Gradient Intensity in Central Europe

10.5194/se-2019-40 ◽

2019 ◽

Author(s):

Maurizio Milano ◽

Maurizio Fedi ◽

J. Derek Fairhead

Keyword(s):

Magnetic Field ◽

Central Europe ◽

Joint Analysis ◽

East European ◽

Long Wavelength ◽

Low Degree ◽

Total Gradient ◽

Synthetic Models ◽

The Magnetic Field ◽

Different Altitudes

Abstract. In the European region, the magnetic field at satellite altitudes (~ 350 km) is mainly defined by a long-wavelength magnetic-low called here the Central Europe Magnetic Low (CEML), located to the southwest of the Trans European Suture Zone (TESZ). We studied this area by a joint analysis of the magnetic and total gradient (∇T) anomaly maps, for a range of different altitudes of 5 km, 100 km and 350 km. Tests on synthetic models showed the usefulness of the joint analysis at various altitudes to identify reverse dipolar anomalies and to characterize areas in which magnetization is weak. By this way we identified areas where either reversely or normally magnetized sources are locally dominant. At a European scale these anomalies are sparse, with a low degree of coalescence effect. The ∇T map indeed presents generally small values within the CEML area, indicating that the Palaeozoic Platform is weakly magnetized. At 350 km altitude, the TESZ effect is largely dominant: with intense ∇T highs above the East European Craton (EEC) and very small values above the Palaeozoic Platform, this again denoting a weakly magnetized crust. Small coalescence effects are masked by the trend of the TESZ. Although we identified sparsely located reversely magnetized sources in the Palaeozoic Platform of the CEML, the joint analysis does not support a model of a generally reversely magnetized crust. Instead, our analysis strongly favors the hypothesis that the CEML anomaly is mainly caused by a sharp contrast between the magnetic properties of EEC and Palaeozoic Platform.

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Remote manipulation of magnetic nanoparticles using magnetic field gradient to promote cancer cell death

10.1101/317115 ◽

2018 ◽

Author(s):

Mahendran Subramanian ◽

Arkadiusz Miaskowski ◽

Stuart Iain Jenkins ◽

Jenson Lim ◽

Jon Dobson

Keyword(s):

Magnetic Field ◽

Magnetic Nanoparticles ◽

Field Gradient ◽

Biomedical Applications ◽

Magnetic Field Gradient ◽

Field Source ◽

Remote Manipulation ◽

Cancer Cell Death ◽

The Magnetic Field

AbstractThe manipulation of magnetic nanoparticles (MNPs) using an external magnetic field, has been demonstrated to be useful in various biomedical applications. Some techniques have evolved utilizing this non-invasive external stimulus but the scientific community widely adopts few, and there is an excellent potential for more novel methods. The primary focus of this study is on understanding the manipulation of MNPs by a time-varying static magnetic field and how this can be used, at different frequencies and displacement, to manipulate cellular function. Here we explore, using numerical modeling, the physical mechanism which underlies this kind of manipulation, and we discuss potential improvements which would enhance such manipulation with its use in biomedical applications, i.e., increasing the MNP response by improving the field parameters. From our observations and other related studies, we infer that such manipulation depends mostly on the magnetic field gradient, the magnetic susceptibility and size of the MNPs, the magnet array oscillating frequency, the viscosity of the medium surrounding MNPs, and the distance between the magnetic field source and the MNPs. Additionally, we demonstrate cytotoxicity in neuroblastoma (SH-SY5Y) and hepatocellular carcinoma (HepG2) cells in vitro. This was induced by incubation with MNPs, followed by exposure to a magnetic field gradient, physically oscillating at various frequencies and displacement amplitudes. Even though this technique reliably produces MNP endocytosis and/or cytotoxicity, a better biophysical understanding is required to develop the mechanism used for this precision manipulation of MNPs, in vitro.

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Magnetorheological Fluids Behaviour in Oscillatory Compression Squeeze: Experimental Testing and Analysis

Acta Mechanica et Automatica ◽

10.2478/ama-2019-0029 ◽

2019 ◽

Vol 13 (4) ◽

pp. 221-225

Author(s):

Wojciech Horak ◽

Marcin Szczęch ◽

Bogdan Sapiński

Keyword(s):

Magnetic Field ◽

Volume Fraction ◽

Experimental Testing ◽

Magnetic Field Gradient ◽

Particle Volume Fraction ◽

Excitation Frequency ◽

Magnetorheological Fluid ◽

Density Level ◽

Particle Volume ◽

The Magnetic Field

Abstract This article deals with experimental testing of magnetorheological fluid (MRF) behaviour in the oscillatory squeeze mode. The authors investigate and analyse the influence of excitation frequency and magnetic field density level on axial force in MRFs that differ in particle volume fraction. The results show that, under certain conditions, the phenomenon of self-sealing can occur as a result of the magnetic field gradient and a vacuum in the working gap of the system.

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Precisely mapping the magnetic field gradient in vacuum with an atom interferometer

Physical Review A ◽

10.1103/physreva.82.061602 ◽

2010 ◽

Vol 82 (6) ◽

Cited By ~ 41

Author(s):

Min-Kang Zhou ◽

Zhong-Kun Hu ◽

Xiao-Chun Duan ◽

Bu-Liang Sun ◽

Jin-Bo Zhao ◽

...

Keyword(s):

Magnetic Field ◽

Field Gradient ◽

Magnetic Field Gradient ◽

Atom Interferometer ◽

The Magnetic Field

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Promising Map-Aided Aircraft Navigation Systems

Giroskopiya i Navigatsiya ◽

10.17285/0869-7035.0055 ◽

2021 ◽

Vol 29 (1) ◽

pp. 32-51

Author(s):

E.V. Karshakov ◽

◽

B.V. Pavlov ◽

M.Yu. Tkhorenko ◽

I.A. Papusha ◽

...

Keyword(s):

Magnetic Field ◽

Field Gradient ◽

Magnetic Field Gradient ◽

Field Measurements ◽

Navigation Systems ◽

Geophysical Field ◽

Airborne Measurements ◽

Aircraft Navigation ◽

Navigation Accuracy ◽

Development Prospects

The paper analyses the development prospects for aircraft navigation systems using onboard geophysical field measurements. Prospective systems that are not widely applied yet are considered: magnetic gradiometers measuring the stationary magnetic field gradient, gravity gradiometers measuring the gravity field gradient, and electromagnetic systems measuring the alternating part of magnetic field. We discuss the main problems to be solved during airborne measurements of these parameters and give an overview of algorithms and hardware solutions. We analyse the results of onboard measurements and estimate the possible navigation accuracy.

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Spectral method for processing hydromagnetic survey data at shallow depths

10.5194/egusphere-egu21-11168 ◽

2021 ◽

Author(s):

Kirill Kuznetsov ◽

Kiryukhina Elena ◽

Bulychev Andrey ◽

Lygin Ivan

Keyword(s):

Magnetic Field ◽

Spectral Method ◽

Magnetic Field Gradient ◽

Geophysical Methods ◽

Temporal Variations ◽

Magnetic Data ◽

Field Reconstruction ◽

Anomalous Magnetic Field ◽

Single Moment ◽

Magnetic Field Variations

Magnetic surveys are commonly used for solving variety of geotechnical and geological challenges in offshore areas, jointly with a set of other geophysical methods. The most popular technique employed is hydromagnetic surveying with towed magnetometers. One of the most significant challenges encountered during processing of the magnetic data is related to temporal variations of the Earth's magnetic field. Accounting for diurnal magnetic field variations is often done by carrying out differential hydromagnetic surveys, a technique developed in the 1980-s. It is based on simultaneous measurements of the magnetic field using two sensors towed behind the vessel with a given separation. This technique allows to calculate along-course gradient which is free of magnetic field temporal variations. This measurement system resembles a gradiometer, with the distance between two sensors being referred to as the base of the gradiometer. It is possible to calculate anomalous magnetic field by integrating obtained magnetic field gradient. Studies have shown that accuracy of its reconstruction decreases with increasing base of the gradiometer. This becomes most significant when distance between the sensors and sources of magnetic field anomalies is small. This situation occur when the survey area is located in shallow water (i.e. for shallow marine, river or lake surveys).An approach for deriving magnetic anomalies and accounting for diurnal variations in differential hydromagnetic surveys based on the frequency (spectral) representation of the measurements was proposed in 1987 [Melikhov, 1987]. This approach utilizes the fact that it is possible to reconstruct the spectrum of magnetic field anomalies along the vessel course from the spectra of measured signals from the first S1(&#969;) and second S2(&#969;) sensors. Assuming that the sensors are located at the same depth, it can be achieved via the following transform:<img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gepj.3d3911bac60061487501161/sdaolpUECMynit/12UGE&app=m&a=0&c=ff23bad5ed5181be02f7ef7ab5e8d6e4&ct=x&pn=gepj.elif&d=1" alt="" width="192" height="43">where &#969; - spatial frequency, l - base of the gradiometer, and i - imaginary unit. Assuming that at a single moment in time magnetic field variations equally affect both sensors, resulting Fourier spectrum T(&#969;) will correspond the spectrum of anomalous magnetic field, free of the magnetic variations. It should be noted that, similar to the along-course gradient integration approach, anomalous magnetic field is restored to a certain accuracy level.Estimates made on model examples showed that accuracy of the field reconstruction using this method is comparable to the accuracy levels of modern marine magnetic surveys (&#177;1-3 nT). It could be noted that for gradiometer bases comparable or larger than depths to magnetic anomaly sources, errors of the field reconstruction are significantly lower for the spectral transformation-based approach compared to along-course gradient integration.References:Melikhov V.R., Bulychev A.A., Shamaro A.M. Spectral method for solving the problem of separating the stationary and variable components of the geomagnetic field in hydromagnetic gradiometric surveys // Electromagnetic research. - Moscow. IZMIRAN, 1987. - P. 97-109. (in Russian)&#160;

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Design and Analysis of a Vibration-Based Magnetoelectric Energy Harvesting Device

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.722.75 ◽

2013 ◽

Vol 722 ◽

pp. 75-80 ◽

Cited By ~ 1

Author(s):

Zhang Zhang ◽

Xian Zhi Dai ◽

Yong Wang

Keyword(s):

Magnetic Field ◽

Cantilever Beam ◽

Magnetic Circuit ◽

Magnetic Field Gradient ◽

Sensor Nodes ◽

Ambient Vibration ◽

Gradient Magnetic Field ◽

Wireless Sensor Nodes ◽

The Magnetic Field ◽

Theoretical Results

An energy harvester is presented to harvest ambient vibration energy using a cantilever beam and multiple Terfenol-D/PMN-PT/Terfenol-D laminate magnetoelectric transducers. The harvester uses eight magnets to make up a magnetic circuit arranged on the free end of the cantilever beam. The magnetic circuit can produce a high gradient magnetic field space. The multiple transducers are placed at the high magnetic field gradient position to make the best use of the magnetic field produced by the magnets. The nonlinear vibration and electrical-output performances of the harvester at resonance are analyzed. The theoretical results indicate that the prototype can produce a load power of 7.619 mW, which is sufficient to supply low consumption wireless sensor nodes.

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