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The total magnetization of an underground magnetic source is the vector sum of the induced magnetization and the natural remanent magnetization. The direction of the total magnetization serves as important a priori information in the inversion and processing of magnetic data. We demonstrated that the total gradient of the magnetic potential with vertical magnetization constitutes the envelope of the vertical component of the magnetic field for all directions of the Earth's field and source magnetization. The total gradient of the magnetic potential with vertical magnetization and the reduction‐to‐the‐pole field simultaneously tend to achieve maximum symmetry near the correct total magnetization direction. As a result, the total magnetization direction can be estimated by computing the correlations between the reduction‐to‐the‐pole and the total gradient of the magnetic potential with vertical magnetization. The proposed method yields accurate magnetization directions in synthetic model examples. The total gradient of the magnetic potential with vertical magnetization is less susceptible to data noise than transforms which are derived from the high‐order magnetic field derivatives or tensors. The estimation results are slightly affected by changes in the source magnetization direction. In a field example in the Weilasito region (North China), the reduction‐to‐the‐pole fields calculated using the estimated magnetization directions are well centred over the source. The proposed method obtained a more focused magnetization direction than that of a three‐dimensional magnetization vector inversion. The total gradient of the magnetic potential with vertical magnetization therefore provides a novel and accurate approach to determine the total magnetization direction from the total field anomaly in a variety of situations. [ABSTRACT FROM AUTHOR]

China's aeromagnetic three-component detection system was successfully developed in 2017, but how to use the three-component data of a large area aeromagnetic field to conduct geological interpretation research is still in the initial stage. This study proposes that the vector map of the total intensity of magnetic anomaly drawn after the aeromagnetic three-component data was significantly facilitated in geological interpretation. The related literature and books have developed the reduction-to-the-pole formula for aeromagnetic three-component data, but it is not final. Therefore, this paper derives the ultimate simple reduction-to-the-pole method based on aeromagnetic three-component data for the first time using a deep theoretical formula. The simple model of a single anomalous body and the complex model of four anomalous bodies are designed. The aeromagnetic three-component data in different latitudes is used to analyze the effect of the aeromagnetic three-component data. The results show that the effect of aeromagnetic three-component data at low latitude is not ideal, and the vector arrowhead of the total intensity of magnetic anomaly drawn after the reduction-to-the-pole method for the aeromagnetic three-component data is studied. The total intensity vector arrowhead of the magnetic anomaly's total strength drawn after the three-component data of the magnetic field can point to the magnetic geological body, and the converged vector arrow's position can reflect the geological body's buried depth. Then, the idea is applied to the aeromagnetic three-component data in the northern part of China, and the vector arrowhead of the total intensity of the magnetic anomaly is drawn. The vector arrowhead diagram of the total intensity of the magnetic anomaly is upward and downward. This study proposes that the different orientation phenomenon of the arrowhead is due to the remanence in the region's magnetic geological body and is verified by comparing the geological data. [ABSTRACT FROM AUTHOR]

The study of the deep structure and tectonics of the Arctic region is relevant not only for solving fundamental problems of modern geodynamics, but also for developing natural resources in the circumpolar regions; it is also of interest from the geopolitical view when determining the boundaries of the marginal seas shelves. To analyze the anomalous magnetic field in the Polar Arctic region, experimental CHAMP satellite data were used, obtained at the last stage of its operation, when the orbit altitude decreased to 280–260 km, which made it possible to obtain geomagnetic parameters with higher spatial resolution. For several sectors of the Polar Arctic, maps of the lithospheric magnetic anomalies field distribution for various scales and degrees of averaging over this area were constructed. The anomalies parameters were analyzed and an explanation was proposed for the geological and physical nature of the anomalies, which are images of the most significant geological–tectonic structures of the North Atlantic Igneous Province and complex of Central Arctic underwater rises. The article discusses the relationships between the discovered features of the lithospheric anomalous magnetic field distribution, and the known geological structures of Amerasia and Eurasia, and tectonic processes that occurred here in the past and still proceed now. The results obtained are of interest for further comprehensive geological and geophysical studies and construction of substantiated models of the Arctic region lithosphere evolution. [ABSTRACT FROM AUTHOR]

The Antarctic Digital Magnetic Anomaly Project is an international research effort to construct a magnetic map of the continent based on ground, satellite, marine, and aeromagnetic surveys. This paper reports the magnetic mapping of the shelf zone in the SE part of the Wilhelm Archipelago, West Antarctica, based on magnetic surveys conducted with Zodiac boats. A spectacular feature of this area is the strong magnetic anomaly of the Antarctic Peninsula (AP) batholith, which was the product of subduction-related Mesozoic–Cenozoic arc magmatism on the former margin of Western Gondwana. We constructed and analyzed a detailed magnetic map of magnetic field anomalies using field observations of rock exposures on the islands and magnetic properties of rocks from laboratory data. The oldest volcanic rocks of Jurassic to Lower Cretaceous age relate to N-NE trending bands of negative magnetic field. The largest feature in the study area is an Upper Cretaceous/Paleogene granodiorite complex that produces a positive magnetic anomaly. Many smaller anomalies are also present over gabbroid bodies of Cretaceous age. Two-dimensional magnetic modeling shows that heterogeneities in the upper crust may have magnetic susceptibilities in the range of 0.005–0.13 SI. Magnetic field anomalies also delineate an orthogonal system of tectonic faults, including the main NE fault along the Penola Strait (sub-parallel to the AP coastline) and four intersecting faults. These fault systems may be associated with different stages of continental margin evolution along the Antarctic Peninsula. [ABSTRACT FROM AUTHOR]

Presently, active detectors are widely used to detect mines, providing high accuracy. However, the principle of the operation of active detectors can lead to the explosion of hidden mines. The novelty of this work is the development of the morphology of a neural network for the classification of mines made of different materials (metallic, semi-metallic, plastic) with high accuracy (99.23%), based on a vector of input features with the following components: the value of the output voltage of the FLC-100 magnetic field sensor, which measures magnetic field anomalies in the vicinity of mines with an accuracy of 10−10–10−4 Tesla; six different soil types, depending on the humidity; and the height at which the magnetic field sensor is located above the mine. Due to the fact that mines, when made of different materials (metallic, semi-metallic, plastic), have different magnetic properties, the neural network method of mine classification, based on the sensor data regarding anomalies of the magnetic field in the vicinity of mines, allows the classification of mines made of different materials. The accuracy of mine classification was assessed with two-layer and three-layer neural networks on various metrics (confusion matrix, ROC curves, accuracy–loss curves), using ADAM, RMSprop, and SGD optimisers, and analyses and comparisons were then carried out. The impact of asymmetry in the neuron number and the types of activation functions in the first and second hidden layers on the values of the accuracy and loss metrics was studied. In particular, it was established that the asymmetry of the number of neurons in the first and second hidden layers relative to the plane of symmetry between the hidden layers has a significant effect on the accuracy of the model (decrease in accuracy by 25%), while the loss function, when the symmetry of the neurons number in the hidden layers is violated, increases to a maximum of 50%. [ABSTRACT FROM AUTHOR]

Craters on Mars are a window into Mars' past and the time they were emplaced. Because the crust is heated and shocked during impact, craters can demagnetize or magnetize the crust depending on the presence or absence of a dynamo field at the time of impact. This concept has been used to constrain dynamo timing. Here, we investigate magnetic anomalies associated with craters larger than 150 km. We find that most of those craters, independent of age, exhibit demagnetization signatures in the form of a central magnetic low. We demonstrate a statistically significant association between such signatures and craters, and hypothesize that the excavation of strongly magnetic crustal material may be an important contribution to the dominance of demagnetized craters. This finding implies that the simple presence or absence of crater demagnetization signatures is not a reliable indicator for the activity of the Martian dynamo during or after crater formation. Plain Language Summary: Craters on Mars allow studying the time at which they were emplaced and as such they are a window into Mars' past. Because the crust is heated and shocked during impact and thus recrystallization occurs, craters can demagnetize or magnetize the crust depending on the presence or absence of a dynamo field at the time of impact. A classic magnetization signature is expressed by a magnetic high in the crater interior and the youngest of those craters have been used to constrain dynamo timing. Here, we investigate magnetic anomalies associated with all craters larger than 150 km. We find that most of those craters and independent of age exhibit a demagnetization signature, and fewer a magnetization signature. In general, the largest craters show a demagnetization signature. To explain the dominance of demagnetization signatures we hypothesize that the excavation of strongly magnetic crustal material may be an important process. This finding implies that the simple presence or absence of crater magnetization signatures is not a reliable indicator for dynamo activity and magnetic signatures of craters are dependent on multiple parameters such as crustal thickness. Key Points: Craters on Mars dominantly show demagnetization signaturesLarge craters and thin crust promote magnetic lows in the crater interior irrespective of dynamo activityCrustal excavation is likely an important process that promotes demagnetization signatures [ABSTRACT FROM AUTHOR]

The three-dimensional magnetic vector structure (magnetization intensity and direction) of the planet can be effectively used to analyze the characteristics of its formation and operation. However, the quick acquisition of a large region of the magnetic vector structure of the planet with bigger observation surfaces undulation is hard and indispensable. We firstly proposed a fast magnetization vector inversion method for the inversion of a magnetic anomaly with the undulating observation surfaces in the spherical coordinate system, which first transforms the data to a plane when the data are distributed on a surface. Then, it uses a block-Toeplitz-Toeplitz-block (BTTB)-FFT to achieve fast inversion with the constraint that the magnetization intensities of the grids between the transformed observation surfaces and the terrain are zero. In addition, Gramian constraint term is used to reduce the ambiguity of the magnetic vector inversion. The theoretical model tests show that the proposed method can effectively improve the computational efficiency by 23 times in the 60 × 60 × 10 grid division compared to the conventional inversion method, and the accuracy of the two computation methods is comparable. The root-mean-square error of the magnetization intensity is only 0.017, and the angle error is within 1°. The magnetization vector structure shows that the largest crater diameter does not exceed 340 km in the Mare Australe region, the amplitude of the magnetic anomaly is much higher than the current meteorite impact simulation results, and the depth of the magnetic source is less than 10 km, which cannot be explained by the impact simulation experiments. In addition, the magnetization directions of adjacent sources differ by 122° (or 238°), and the high-frequency dynamics of the Moon as well as the short-lived dynamics may be responsible for this phenomenon. The magnetization directions of the three adjacent sources in the Mare Crisium region are close to each other and differ in depth with different cooling times, making it difficult to record the transient fields produced by meteorite impacts. In addition to the above characteristics, the magnetization direction of the magnetic sources in both regions is uniformly distributed without reflecting the dispersion of the magnetization direction of the meteorite impact magnetic field. Therefore, it can be inferred that the magnetic anomalies in these two regions are related to the generator hypothesis. [ABSTRACT FROM AUTHOR]

The spatial distribution of the lithospheric magnetic anomalies field obtained from German CHAMP satellite measurements for several years of its mission is investigated over the territory of the Indo-Asian collision, in particular, the Tarim region and the Western Himalayan syntax (WHS). Maps of the total intensity Ta of the lithospheric magnetic field for these regions are given. The lithospheric magnetic anomalies field as a reflection of the consequences of the Indian lithospheric plate subduction under the Eurasian plate is discussed in the context of modern ideas about the geological and tectonic structure and geophysical processes of the region. The sign inversion of the magnetic anomalies over the northern part of the Indian Plate observed on Ta maps is supposed as a result of the lower crust heating due to mantle processes, the rise of the Curie isotherm and, as a consequence, the loss of the initial magnetization of the lower crust. In order to study the WHS territory and its surroundings in detail, maps of the lithospheric magnetic anomalies field are constructed at the lowest level of CHAMP orbit as possible, which leads to an increase in their resolution by nearing the field sources. The relationship of detected regional anomalies with tectonic processes in this seismically active area and with other available geophysical information is discussed. An interpretation of the obtained information shows that the images of lithospheric magnetic anomalies distinctly correlate with modern view about the location of large-scale geological and tectonic structures. [ABSTRACT FROM AUTHOR]

The spatial distribution of the field of lithospheric magnetic anomalies carries information about its sources—deep tectonic structures—and reflects the processes occurring at mantle depths. Based on the geomagnetic data measured by the CHAMP satellite at an observation altitude of ~290 km, the lithospheric magnetic field parameters over the territory of Africa were calculated. A series of lithospheric magnetic anomalies of the total intensity Ta maps of various scales and degrees have been constructed. The distribution of Ta over the territories of Southern and East Africa is given. An analysis of lithospheric magnetic anomalies maps over the territories of African superplume influence showed good agreement with the existing hypothesis about the passage of the mantle superplume flow from the lower mantle to the upper mantle in the northeast direction and its further continuation under the East African rift zone. The parameters of the anomalous lithospheric magnetic field contain information about the magnetization of the lithosphere deep layers, reflecting the magnetic properties of large regional tectonic structures and the topography of the Curie surface, which is associated with the geothermal regime and tectonic setting at different levels of the lithosphere. This work shows the perspective of the geomagnetic field satellite observations using in the study of the tectonics of active zones and mapping of deep lithosphere heterogeneities in hard-to-reach areas. [ABSTRACT FROM AUTHOR]

The tectonosphere and formation conditions of the Mozambique Ridge are considered. The Mozambique Ridge is located in the southwestern part of the Indian Ocean between the Natal and the Mozambique Mesozoic basins. The formation of the ridge is still debatable issue. The anomalous structure of the crust of the Mozambique Ridge can be explained either by underplating (thickening of the oceanic crust from below due to magmatism) or by stretching and thinning of the continental crust. Based on gravity and magnetic field anomalies, seismotomography and other geological and geophysical data, density modeling along four profiles was carried out. Physical modeling determined the formation conditions of the Mozambique Ridge, which was formed due to the splitting of the African–Antarctic continent, the presence of structural heterogeneities in the lithosphere of the African continent, and the influence of the Karoo plume. [ABSTRACT FROM AUTHOR]

We investigate the total intensity F of the lithospheric field over the Xinjiang region (34–50° N, 73–96.5° E) through a three-dimensional surface spline (3DSS) model with 0.1° × 0.1° resolution, constrained by 296 ground measuring points recorded between 1936.0 and 2000.0, 10,236 aeromagnetic data points during 1970–2011, and 10,236 satellite model predictions of CHAOS-7.5. We compare predictions of the new model against those from the regional spherical harmonic (RSH) model, two-dimensional surface spline and Taylor polynomial models, and global models LCS-1 and NGDC720. We select 13,605, 18,723, and 23,841 points from three altitudes to create 3DSSS (sparse), 3DSSM (middle), 3DSSD (dense) models, allowing for external field contamination and boundary effects. Results show a good agreement between the spatially detailed 3DSS model and aeromagnetic data. The new model reveals lower error after inspecting the residuals and root mean square error (RMSE), the coefficients, and correlation coefficients between 3DSS models. The new model enables useful geological interpretation; four magnetic anomalies of Xinjiang are coincident with geological structures, and anomalies are also consistent with the tectonic facies and especially the geological distribution in eastern Tianshan. The lithospheric magnetic field in the research area reflects the magnetization difference of the basement, and its geological origin is ascribed to multi-stage magmatism. Results imply that the 3DSS model can model the spatial distributions robustly and is not sensitive to the number of modeling points. The induced field dominates the continent and has a magnetization process in the WE direction in Xinjiang. [ABSTRACT FROM AUTHOR]

An actual problem today is the search for observed evidence of the existence of deep small-scale magnetic fields of the Sun. In this regard, the authors analyzed the theoretical criterion for separating the contributions to the solar surface magnetism of two qualitatively different mechanisms of a small-scale dynamo, the action of which is hidden in the depths of the solar convection zone (SCZ), proposed by Sokoloff and Khlystova [Astron. Nachr. 2010. 331. P. 82–87]. The first mechanism ensures the generation of small-scale magnetic fields due to the interaction of turbulent motions with the mean magnetic field (small-scale dynamo-1 of macroscopic MHD), while the second mechanism causes self-excitation of magnetic fluctuations due to turbulent pulsations of highly conductive plasma (diffusive small-scale dynamo-2 of classical MHD). The essence of the proposed criterion is that deep small-scale magnetic fields can lead under certain conditions to violations of Hale's and Joy's laws of observed magnetism on the surface of the Sun. Statistical analysis of these disturbances allows one to identify the differences in the evolution of the observed manifestations of two sources of small-scale fields since the contribution of two deep dynamo mechanisms to surface magnetism varies with the phase of the solar cycle in different ways. Such an important feature is the behavior of the percentage of anti-Hail groups of sunspots (in relation to the total number of sunspots) during the cycles. In the case of small-scale dynamo-1, the percentage of anti-Hale groups is independent of cycle phase, whereas the percentage of anti-Hale groups associated with diffusive small-scale dynamo-2 should reach its maximum value at solar minima. Therefore, the variations of magnetic anomalies make it possible to separate the meager contributions of two small-scale dynamo mechanisms to surface magnetism. In this connection, the task of identifying the markers of a small-scale dynamo in the solar depths from observations becomes relevant. With this in mind, we conducted an analysis of literature data of statistical studies of long series of observed violations of Hale's and Joy's laws, which can be caused by the presence of deep small-scale magnetic fluctuations of various origins. In particular, it was demonstrated in the work of Sokoloff, Khlystova, and Abramenko [Mon. Notic. Roy. Astron. Soc. 2015. 451. P. 1522–1527] on the basis of processing the data of different catalogs for the period 1917–2004 that the percentage of anti-Hale groups of spots increases during the minima of solar cycles. This testifies to the operation of a diffusive small-scale turbulent dynamo-2 within the SCZ, the efficiency of which becomes noticeable near the minima of the cycles, when the global toroidal magnetic field weakens. As a result of the authors' analysis of six magnetic active regions observed near the minima of the 24th and 25th solar cycles, characteristic violations of Hale's and Joy's laws were revealed, which may indicate the influence of a diffusive small-scale dynamo-2 on the evolution of these regions since it is this source that gives the most noticeable contribution in surface magnetism near cycles minima. [ABSTRACT FROM AUTHOR]

The geophysical survey on cruise 42 of the R/V Akademik Boris Petrov (2017) in the survey area near site 758 ODP significantly refined knowscarp about the bottom topography of the northern segment of the Ninetyeast Ridge. It is crossed by E–W transversal linear troughs, which are apparently young tectonic fractures. The morphology of the narrow elevated block in the central part of the deep depression between neighboring large volcanic edifices has been characterized in detail. In addition to linear tectonic structures, the main features of this block are two volcanic seamounts. A detailed magnetic survey in this area identified for the first time the nature of sources of magnetic anomalies on the Ninetyeast Ridge. Intense local magnetic anomalies have been observed here, both confined to local structures of the bottom and basement relief, and clearly unrelated to them. These anomalies have a complex interfering nature caused by the superposition of fields from sources separated by magnetization, spatial position, and age. According to the results of paleomagnetic analysis of the anomalies, the age of the structures here is very wide: the youngest features formed about 20 Ma ago, and the oldest, over 80 Ma ago. [ABSTRACT FROM AUTHOR]

The parent impact crater of Australasian tektites has not been discovered so far, but a consensus has been accepted on its location in a wider area of Indochina. Recently, an alternative location has been suggested in the Badain Jaran Desert (BJD), Northwest China. Employing gravity and magnetic data derived from satellites, possible presence of an impact structure in BJD is investigated. The gravity parameters include the free air gravity disturbance, its vertical derivative component and total horizontal gradient (THG), strike alignment (SA), and Bouguer anomaly with its first vertical derivative and tilt angle. The magnetic parameters include the anomalous total magnetic field (TMF), its reduced to the pole transformation (RTP), the first vertical derivative of the TMF vertical component (Bzz), tilt angle (TA), and logistic total horizontal gradient (LTHG). Both the gravity and magnetic indicators support the presence of the impact structure. Gravity parameters display typical annular gravity highs circumscribing a gravity low. SA analysis reveals preferred parallel directions, implying the susceptibility of special zones to the impact shock waves, both within and beyond the rim. TMF reveals a large magnetic anomaly in the southern part of the proposed crater, and RTP displaces and restricts it further into the rim. Bzz weakens the long wavelength anomalies, amplifies the superficial ones, and separates them horizontally. TA and LTHG delineate the deep-seated and shallow magnetic signals related to the peak and border magnetization, respectively. [ABSTRACT FROM AUTHOR]

Owing to its unevenly distributed crustal fields, Mars acts as a unique obstacle to the solar wind. In the presence of the crustal fields, the transport of the planetary ions on the dayside ionosphere exhibits north–south asymmetry. Additionally, the heavy-ion loss in the magnetotail is affected by the crustal fields. In this paper, a three-dimensional multispecies magnetohydrodynamic model is employed to simulate Mars–solar wind interactions. Numerical results indicate that the meridional transport is dominant in most areas on the dayside ionosphere. In the presence of the crustal fields, the meridional transport on the southern hemisphere (southward transport) is reduced by more than 70% above the strong crustal sources, and the zonal velocity shows local changes inside strong and weak crustal field regions. These effects result in an increase or decrease in the number density of the heavy ions reaching the terminator, thereby influencing the thickness of the ionosphere. Decreased southward velocity leads to a reduction in the heavy-ion loss on the southern magnetotail. The radial outward flux is reduced by more than 30% for O2+ and CO2+ and by 10% for O+. This study shows that in addition to the zonal transport, the meridional transport is important for the day-to-night transport on the dayside of Mars. Collectively, the horizontal plasma transport, controlled by crustal fields, is associated with the altered ionosphere structure and reduced heavy-ion loss in the magnetotail. [ABSTRACT FROM AUTHOR]

Old mining districts have created numerous subsurface cavities, often at shallow depths. The resulting subsidence risk is a major territorial planning problem, especially when these holes are in urban expansion areas. Ground-penetrating radar (GPR) and magnetic techniques can help to detect and to characterise these shallow mining structures based on the strong contrast of electromagnetic and magnetic properties (dielectric constant and magnetic susceptibility) between the rock and the backfill of cavities. In the present study, these techniques were used to locate old mining cavities near the city of Linares, located south of Spain and connected to the area's old mining district. GPR and magnetometry (total magnetic field and vertical magnetic gradient) were performed on a grid in one of the most important veins in the sector. By comparing both working methods, the vein structure within the granite can be detected. On the one hand, the magnetic prospecting technique (magnetic anomalies) has allowed us to detect when the vein is covered by metallic elements of natural or anthropogenic origin. On the other hand, strong reflections and hyperbolic events associated in GPR profiles confirm the presence of cavities related to old mining operations. Shallow magnetic anomalies not associated to GPR variations are related to the slag present in the study area (detected in the outcrop) or to unexploited vein mineralizations. [ABSTRACT FROM AUTHOR]

The parent impact crater of Australasian tektites has not been discovered so far, but a consensus has been accepted on its location in a wider area of Indochina. Recently, an alternative location has been suggested in the Badain Jaran Desert (BJD), Northwest China. Employing gravity and magnetic data derived from satellites, possible presence of an impact structure in BJD is investigated. The gravity parameters include the free air gravity disturbance, its vertical derivative component and total horizontal gradient (THG), strike alignment (SA), and Bouguer anomaly with its first vertical derivative and tilt angle. The magnetic parameters include the anomalous total magnetic field (TMF), its reduced to the pole transformation (RTP), the first vertical derivative of the TMF vertical component (Bzz), tilt angle (TA), and logistic total horizontal gradient (LTHG). Both the gravity and magnetic indicators support the presence of the impact structure. Gravity parameters display typical annular gravity highs circumscribing a gravity low. SA analysis reveals preferred parallel directions, implying the susceptibility of special zones to the impact shock waves, both within and beyond the rim. TMF reveals a large magnetic anomaly in the southern part of the proposed crater, and RTP displaces and restricts it further into the rim. Bzz weakens the long wavelength anomalies, amplifies the superficial ones, and separates them horizontally. TA and LTHG delineate the deep-seated and shallow magnetic signals related to the peak and border magnetization, respectively. [ABSTRACT FROM AUTHOR]

The Earth's crust is exceptionally important to understand the geological evolution of our planet and to access natural resources as minerals, critical raw materials, geothermal energy, water, hydrocarbons, etc.. However, in many regions of the world it is still poorly modelled and understood. Here we present the latest advance on three-dimensional modelling of the Mediterranean Sea crust based on freely available global gravity and magnetic field models. The proposed model, based on the inversion of gravity and magnetic field anomalies constrained by available a-priori information (such as interpreted seismic profiles, previous studies, etc.), provides, with an unprecedented spatial resolution of 15 km, the depths of the main modelled geological horizons (Plio-Quaternary, Messinian and Pre-Messinian sediments, crystalline crust and upper mantle), coherent with the known available constraints, together with the three-dimensional distribution of density and magnetic susceptibility. The inversion is carried out by means of a Bayesian algorithm, which allows to modify at the same time the geometries and the three dimensional distributions of density and magnetic susceptibility, always respecting the constraints introduced by the initial information. In addition to unveil the structure of the crust beneath the Mediterranean Sea, the present study also shows the informative content of freely available global gravity and magnetic models, thus putting the base for the development of future high resolution models of the Earth crust at global level. [ABSTRACT FROM AUTHOR]

We perform a statistical investigation of the occurrence rates of energetic electron (100–500 eV) pancake pitch-angle distributions (PADs) in the Martian space environment by utilizing 6 yr of MAVEN data. In the Martian ionosphere, we find the following: (1) at the same altitude in the terminator and night regions, the occurrences rates in the center of the southern magnetic anomaly regions are very low, but at the edges of strong magnetic fields, they increase significantly; (2) the occurrence rates of energetic electron perpendicular anisotropies on the Martian dayside increase with altitude; and (3) some closed magnetic lines in the 10°S–55°S, 30°W–125°W region at 400–800 km altitude gradually become open during the rotation of Mars from duskside to dawnside, while more closed magnetic lines are produced in the 40°S–65°S, 35°E–90°E region. In the Martian induced magnetosphere, we find the following: (1) the high-energy electron perpendicular anisotropy in the magnetosheath is the most significant; (2) the occurrence rates in the southern (Z MSO ≤−1 R M) magnetosheath are higher than those in the northern (Z MSO ≥ 1 R M) magnetosheath; (3) in the region of ∣ Z MSO∣ < 0.5 R M, these high-energy electron pancake PADs are mainly concentrated in the magnetosheath region with Y MSO ∈ [−1.4RM, 2 R M]; (4) the occurrence rates in the dawnside (Y MSO ≤−1 R M) magnetosheath are higher than those in the duskside (Y MSO ≥ 1 R M) magnetosheath; and (5) in the region of ∣ Y MSO∣ < 0.5 R M, the occurrence rates throughout the magnetosheath are very high. [ABSTRACT FROM AUTHOR]

Understanding the seismo–ionospheric coupling mechanism requires a quiet geomagnetic condition, as this represents an ideal situation to detect abnormal variations in the geomagnetic field. In reality, continuous interactions between solar wind and Earth's magnetosphere create many fluctuations in the geomagnetic field that are more related to sun–magnetosphere interactions than to seismotectonic causes. A triaxial magnetometer was installed at the Muntele Rosu Observatory near the Vrancea seismic zone in 1996 to measure the local magnetic field. Since 2002, the data have become more consistent, allowing for the representation of long time series. Since then, variations have been observed on the eastern component (By) of the magnetic field, which sometimes overlaps with significant earthquakes. Previous studies have shown that high decreases in amplitude recorded on the By component of the magnetic field measured at Muntele Rosu have been accompanied by higher seismicity, while small decreases have been accompanied by lower seismic energy release. This research analyzes the geomagnetic data collected between September 2002 and May 2008 from two geomagnetic observatories, one located in the proximity of the Vrancea seismic zone and another one situated 120 km away. For each geomagnetic anomaly identified, the daily seismic energy released was plotted logarithmically, along with seismicity and Kp indices. Additionally, the daily seismic energy released was also plotted logarithmically for all earthquakes with Mw ≥3. To identify variations in the By component, datasets recorded at Muntele Rosu (MLR) were compared with those recorded at Surlari National Geomagnetic Observatory (SUA), to discriminate between global magnetic variations associated with solar activity and possible seismo–electromagnetic variations. The standard deviation (SDBy) was calculated for each anomaly recorded on the By component of the magnetic field and compared with the cumulative seismic energy release. To determine if this type of variation was present in other components of the magnetic field, the following ratios were calculated for all data recorded at Muntele Rosu: Bz/Bx, Bz/By, and Bz/BH. The size of the anomalies resulting from the standard deviation measured on the By component (SDBy) partially validates the relationship between the size of the anomalies and the seismic energy release during the anomaly. The relationship between the released seismic energy and the anomaly magnitude is vaguely respected, but these variations seem to follow two patterns. One pattern is described by smooth decreases, and the other pattern involves decreases where the By component varies significantly over short periods, generating decreases/increases in steps. It was noticed that seismic activity is greater for the second pattern. Additionally, using standard deviation measured on the magnetic field represents a great tool to discriminate external magnetic field variations from local, possibly seismo–magnetic variations. [ABSTRACT FROM AUTHOR]

The Earth's crust is exceptionally important to understand the geological evolution of our planet and to access natural resources as minerals, critical raw materials, geothermal energy, water, hydrocarbons, etc.. However, in many regions of the world it is still poorly modelled and understood. Here we present the latest advance on three-dimensional modelling of the Mediterranean Sea crust based on freely available global gravity and magnetic field models. The proposed model, based on the inversion of gravity and magnetic field anomalies constrained by available a-priori information (such as interpreted seismic profiles, previous studies, etc.), provides, with an unprecedented spatial resolution of 15 km, the depths of the main modelled geological horizons (Plio-Quaternary, Messinian and Pre-Messinian sediments, crystalline crust and upper mantle), coherent with the known available constraints, together with the three-dimensional distribution of density and magnetic susceptibility. The inversion is carried out by means of a Bayesian algorithm, which allows to modify at the same time the geometries and the three dimensional distributions of density and magnetic susceptibility, always respecting the constraints introduced by the initial information. In addition to unveil the structure of the crust beneath the Mediterranean Sea, the present study also shows the informative content of freely available global gravity and magnetic models, thus putting the base for the development of future high resolution models of the Earth crust at global level. [ABSTRACT FROM AUTHOR]

We report the caloric and magnetocaloric properties of the DyxY3−xAl5O12 garnet single crystals (x = 0, 0.15, 0.5, 1, 1.5, 2.25, 3) studied within a large temperature range at magnetic fields up to 70 kOe. Heat capacity at zero field revealed that the Schottky anomalies ascribed to magnetic splitting the ground Kramers doublet of Dy3+ ions induced by neighbor ions. The low-temperature heat capacity was fitted by a sum of the Debye and Schottky contributions. The antiferromagnetic transition above 1.9 K was observed only for the pure dysprosium aluminum garnet. The shifts of the Schottky anomalies in magnetic fields agreed with strong anisotropy of the g-factor of Dy3+ ions in the c-sites. The Dy3+ ions in the non-stoichiometric positions caused additional weak anomalies in the heat capacity. The heat capacity for the garnet with x = 1 demonstrated strong clustering for this particular composition. The results obtained showed that the measurements of the heat capacity in magnetic field can be used to get information on substitutional disorder and non-stoichiometry in solid solutions. The magnetic entropy was evaluated for the dysprosium-comprising garnets. The pronounced magnitude of the magnetic entropy owing to the Schottky anomalies shows the applicability of the mixed dysprosium yttrium garnets to adiabatic refrigerators. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive approach to mapping local magnetic field anomalies with robustness to magnetic noise from an unmanned aerial vehicle (UAV). The UAV collects magnetic field measurements, which are used to generate a local magnetic field map through Gaussian process regression (GPR). The research identifies two categories of magnetic noise originating from the UAV's electronics, adversely affecting map precision. First, this paper delineates a zero-mean noise arising from high-frequency motor commands issued by the UAV's flight controller. To mitigate this noise, the study proposes adjusting a specific gain in the vehicle's PID controller. Next, our research reveals that the UAV generates a time-varying magnetic bias that fluctuates throughout experimental trials. To address this issue, a novel compromise mapping technique is introduced, enabling the map to learn these time-varying biases with data collected from multiple flights. The compromise map circumvents excessive computational demands without sacrificing mapping accuracy by constraining the number of prediction points used for regression. A comparative analysis of the magnetic field maps' accuracy and the spatial density of observations employed in map construction is then conducted. This examination serves as a guideline for best practices when designing trajectories for local magnetic field mapping. Furthermore, the study presents a novel consistency metric intended to determine whether predictions from a GPR magnetic field map should be retained or discarded during state estimation. Empirical evidence from over 120 flight tests substantiates the efficacy of the proposed methodologies. The data are made publicly accessible to facilitate future research endeavors. [ABSTRACT FROM AUTHOR]

To solve the problem of optimal course of anti-submarine aircraft in the process of searching submarine using magnetic detector, three indexes and a method for evaluating the ability of anti-submarine aircraft searching submarine by magnetic detector with different courses are proposed, on the basis of modeling and analysis of submarine magnetic field. Then the ability above is simulated and analyzed, and the result shows that the anti-submarine aircraft has the best detection effect along the north and south direction, and the worst detection effect along the east and west direction. [ABSTRACT FROM AUTHOR]

Our multiyear studies have enabled us to make maps showing magnetic anomalies ΔTa for major geothermal systems in the Pauzhetka area of southern Kamchatka. Magnetic fields possess both general characteristics and individual features for each object of study. The Nizhne-Koshelev vapor-dominated geothermal field is identified on the basis of a set of linear negative magnetic anomalies confined to thermal-controlling tectonic faults. The Pauzhetka geothermal field is characterized by an inhomogeneous structure of the anomalous magnetic field ΔTa: the northwestern area has a quiet, slightly negative magnetic field, showing that this part of the field is dominated by lateral spreading of hydrothermal fluids from the upper aquifer; the southeastern part has numerous sign-varying magnetic anomalies of high intensity confined to acid–intermediate subvolcanic bodies. The South Kambalnyi group of thermal fields is characterized by a lower absolute value of magnetic induction Т compared with the Pauzhetka and the Nizhne-Koshelev geothermal fields, showing that the rocks of the Kambalnyi volcanic range are more intensely altered by hydrothermal and metasomatic processes, probably as a result of a long-continued action of convective heat flow. [ABSTRACT FROM AUTHOR]

The noise-like behavior of the geomagnetic anomalies observed in Tlamacas station (volcano Popocatepetl, Mexico), linked to the ionization produced by intensive radon release, are presented in the experimental part of this study. The magnetic field perturbations produced by charge spreading currents within the fair-weather electric field are considered in the theoretical model based on the electrode. The electric charges are generated by the air ionization due to radon emanation. The simulations demonstrated that the ionization of the air leads to magnetic field perturbations of about 0.001–0.1 nT in the ULF (ultra low frequency) range 10−3–10−1 Hz. Magnetic field perturbations can be higher when the radon emanation occurs in a region with terrain irregularities. [ABSTRACT FROM AUTHOR]

Marine magnetic field surveys conducted near the sea bottom are useful in producing images of the oceanic crust in order to ascertain its volcanic eruption history, active hydrothermal systems, and hydrothermal deposit evolution. An autonomous underwater vehicle (AUV) can carry out self-controlled survey operations while maintaining a stable vehicle attitude at low altitudes above the seafloor. As a result of these benefits, AUVs have attracted attention for various missions. The total magnetic field intensity is generally used for subsurface magnetization images. Recently, vector magnetic anomaly analysis has been considered to be extremely effective for high-accuracy estimation of subsurface magnetization structures. However, correcting for the anomalous magnetic field produced by the vehicle body is one of the difficulties that hinders vector magnetic anomaly analysis. Therefore, we developed a magnetometer system designed for the AUV URASHIMA with a renewed navigation data distribution system. Experimental observation was carried out around a submarine mud volcano with a small magnetic anomaly off Tanegashima Island. The results show that correction for the magnetic field of the vehicle because of the attitude, especially for changes in pitch, is essential for near-bottom magnetic surveys using AUVs. Based on these results, we proposed a suitable data acquisition method to remove the pitching effects of the vehicle for figure-eight turns. Next, practical observation was carried out in the hydrothermal area, and the proposed correction method for magnetic data reduced the pitch variation effect. These results indicate that the correction for the magnetic field of the vehicle based using attitude data, especially for pitching variations, is required in order to obtain high-quality magnetic anomaly data using AUVs. However, a short-period variation of approximately 10 nT caused by abrupt pitch changes remains. [ABSTRACT FROM AUTHOR]

Since Türkiye's territory is mostly mountainous and forested, earth science studies in these areas have not been completed at an adequate level and with a satisfying resolution. However, due to the long time and cost of collecting measurements from land in large- and medium-scale studies and due to the inability to collect measurements in regular grid intervals in large-scale studies to be carried out on land, an airborne geophysical survey project was conducted in order to collect high-resolution magnetic and radiometric country-scale data. Total magnetic field and radiometry data were collected from the air between 2017 and 2022 within the scope of the country-wide Airborne Geophysics Surveys Project. The data collection flights were carried out in such a way as to follow the topography from an altitude of about 200 m above the ground. The flights were carried out considering the regular geometry of the flight profile and the general geological and tectonic structure of Türkiye in the direction of N-S with one-kilometer profile intervals. A total field magnetic anomaly map was obtained after applying the diurnal, tie line leveling, IGRF (model 2020), and differential reduction to magnetic pole (DRTP) corrections to the magnetic data. For the scope of this study, the total field magnetic anomaly and the regional total field magnetic anomaly maps were presented along with the structural boundary maps (tilt angle (TA), the total horizontal derivative (THDR) and the analytical signal (AS)) derived from these maps. During another stage of the study, the general tectonic structure of Türkiye and structural boundaries obtained from derivative-based maps (AS, TA, and THDR) were compared. General geophysical interpretation was also performed with magnetic-anomaly and derivative-based maps for the three regions characterized by high magnetic anomalies. [ABSTRACT FROM AUTHOR]

In the field of aviation anti-submarine warfare, magnetic detection systems often result in a large number of false alarms due to the inability to effectively distinguish between a local geomagnetic anomaly in the background field and a target magnetic anomaly. To address this problem, this paper proposes a matching detection method for the magnetic anomaly of underwater targets. This method is based on the measured data of the magnetic anomaly in the sea area, and the geomagnetic reference map of the area is generated by interpolation of the Kriging method; then, the background field signal extracted from the geomagnetic reference map and the real-time signal acquired by detection are matched by the similarity metric algorithm; finally, the target detection is realized by using the feature fusion-isolation forest algorithm. Compared with the conventional detection methods, such as time–frequency analysis, the detection rate is improved by nearly 15% and the false alarm rate is reduced by about 40%, indicating that matching detection can effectively filter out the magnetic anomaly in the background field, reduce the false alarm, and improve the detection rate in the real geomagnetic environment, which has certain application value. [ABSTRACT FROM AUTHOR]

This paper introduces a news processing method for geomagnetic anomaly field data: envelope mode magnetic field, which can weaken the influence caused by geomagnetic polarity reversal during rock magnetization, reflect the magnetic change of crustal rocks, and locate the crustal structures. According to the characteristics of the magnetic anomaly field, the envelope mode magnetic field is calculated in three different ways: full anomaly envelope, positive anomaly envelope, and negative anomaly envelope. The simulation test of seismic signal and magnetic anomaly model has achieved good results. During the calculation of the real-world data, because the magnetization directions of the geomagnetic field in the southern and northern hemispheres are opposite, we use the full envelope or positive envelope method for the northern hemisphere and the negative envelope method for the southern hemisphere. The experiment using EMAG2 global satellite magnetic anomaly data demonstrates that the strong anomaly of the envelope mode magnetic field is consistent with the spatial distribution of cratonic tectonic units, confirming its application effect. [ABSTRACT FROM AUTHOR]

Near‐real time analysis of magnetization can provide important information for the imaging of volcano systems and their spatiotemporal evolution. This study focuses on the contribution of volcano‐magnetic signals from reiterations of ground magnetic measurements to investigate the evolution of active structures at the Piton de la Fournaise volcano from 2017 to 2020. Changes are demonstrated by magnetic anomalies along a reference profile by means of the reiteration periods. These variations are first modeled qualitatively in 2D using electrical resistivity constraints in order to investigate the evolution of magnetization at depth through time, and the model is subsequently compared with the 3D intrusive activity from depth up to the surface from Interferometric Synthetic Aperture Radar (InSAR) inverse modeling. The shallow areas of demagnetization modeled from one reiteration to another are consistent with the geometry and location of the underlying intrusions revealed by the 3D InSAR models, suggesting strong thermal, stress, and electrokinetic effects due to magmatic activity not only at the surface but also at depth, along the main magmatic paths. It also raises a question as to the extent of the associated thermal diffusion processes at the scale of individual magma injections. This study confirms that detecting resistivity and magnetization anomalies, and quantifying their spatiotemporal evolution, can provide powerful tools for imaging volcanic systems at various scales and for providing warning of associated hazards. It also highlights the necessity for 4D monitoring of volcanic edifices using this method to provide greater precision, an important issue that is now made possible by the use of Unmanned Aerial Vehicle measurements. Plain Language Summary: Volcanic activity (through volcano‐tectonic, magmatic, and hydrothermal processes) undeniably disturbs the magnetic field, especially at a local scale. Recent studies have evidenced the potential of magnetic field measurements in imaging thermal anomalies (strong influence of temperature on magnetic measurements) and mechanical heterogeneities (fracturing‐alteration). Piton de la Fournaise (La Réunion Island, Indian Ocean) is an outstanding target to address such issues, being highly active and closely monitored. In this study, we used repeated magnetic measurements conducted over 3 years along a 3,780‐m‐length profile close to the summit of Piton de la Fournaise. We used the complementarities between magnetization and electrical resistivity parameters in a 2D magnetic modeling approach, in order to image the consequence of the eruptive dynamics on the edifice structure at depth. The temporal evolution of the magnetic anomalies appears strongly correlated to the depths and volumes of magmatic intrusions along the main active area. These results open new perspectives in studying the spatiotemporal changes in magmatic, hydrothermal, and mechanical changes and alteration processes within volcanic edifices. Key Points: Volcano‐magnetic variations at Piton de la Fournaise volcano (magmatic and mechanical changes, hydrothermal alteration processes)2D modeling of magnetic anomalies evolution under electrical resistivity constraints consistent with Interferometric Synthetic Aperture Radar 3D intrusions modelsImaging the main paths of weakness at depth that could be associated with potential future magmatic transfers [ABSTRACT FROM AUTHOR]

Methods are described for estimating the sensitivity characteristics of a vibration induction transducer designed to monitor the discontinuity of the surface of objects when they are magnetized by an applied constant field. Based on analysis of the mathematical model of the output signal of the vibration-induction transducer, analytical expressions are obtained for the conversion factors of the rate of change in the magnetic field intensity and acceleration along the coordinate of the vibration displacement of the transducer in the EMF induction coil. Methods of experimental estimation of the conversion factors are given, and the high convergence of calculated and experimental estimates is shown. Based on the formulated conditions for the detection of magnetic field anomalies arising on the defective surface areas and the known values of the conversion factors, calculated ratios were derived to estimate the sensitivity thresholds of the transducer according to the orthogonal components of the magnetic field intensity distribution. As a result of experimental verification, the adequacy of the calculated and experimental estimates of the sensitivity thresholds was confirmed. Recommendations are given for the application of computational and experimental methods for assessing the sensitivity characteristics of a vibration induction transducer. [ABSTRACT FROM AUTHOR]

The paper presents the results of laboratory experiment modeling the interaction between Lunar magnetic anomalies and Solar wind. To model the LMA we use quadrupole magnetic field. The main dimensionless parameter of the problem, the ion inertia length relative to the mini-magnetosphere size, well corresponds between experiment and LMA conditions. The main result is measurement of the magnetically reflected proton fluxes, which show qualitative agreement to available satellite data. [ABSTRACT FROM AUTHOR]

The separation of the effects of deep-seated sources of potential fields from those of shallower ones is a frequent requirement when interpreting magnetic or gravity fields. A common procedure is estimating the regional, long wavelength, component of the field by analysing the data over an area larger than that of the local feature of interest. The local components are found by subtracting the estimated regional from the observed data. These approaches may have difficulties in their application, as the dataset over large areas may not be available and other local anomalies, in the enlarged area, may prevent a reliable estimate of the regional field. We present an alternative and simple approach to the regional-residual separation problem not requiring the analysis over large areas and aiming at estimating the local, rather than the regional, component. Our method exploits the natural enhancement of short wavelengths obtainable by computing vertical derivatives of potential fields. An equivalent layer source is computed from the vertical derivative and is used to estimate the local field. The optimal differentiation order can be determined by inspecting the obtained results. This parameter may assume even fractional values, so that the method results a very versatile tool. The application to a complex synthetic case and two real data examples demonstrates the utility of this approach. In summary, our method has some peculiar characteristics making it an interesting alternative to currently used approaches to regional-residual separation: (i) it is a local method, so it can work well even when processing datasets relative to areas of limited extension; (ii) unlike most current methods, estimating a smooth regional component, our method directly produces an estimate of the local field and (iii) it is highly versatile, as the key parameter, that is the fractional differentiation order, can be finely adjusted up to obtain an optimal local field. [ABSTRACT FROM AUTHOR]

The relationship between the spatial distribution of the lithospheric magnetic anomalies obtained from the data of the German CHAMP satellite and the marker of tectonic processes caused by the movement of the African superplume is considered. Measurements of the geomagnetic field total intensity by the CHAMP satellite at altitudes of ~290–260 km above the area with coordinates 12°–44° E and 30° S–16° N are used as the data source. Analysis of the maps constructed from these data shows that the distribution of the negative magnetic anomalies is consistent with the dominant northeastern vector of the African superplume mantle flow. Due to the heating of the lithosphere by the mantle superplume substance, when the Curie temperature values near 580° are reached, the magnetized structures of the lower crust losetheir magnetic properties, so the trajectory of the mantle flow is "tracked". The concordance of the lithospheric magnetic anomalies distribution to one of two hypothesis on the Ethiopia/Afar plume and its hotspot position is analyzed: either in the territory of the Afar depression, or in the area of the Main Ethiopian rift. The negative magnetic anomalies are fixed directly above the Main Ethiopian Rift, which confirms the second tectonic hypothesis. According to the available seismic studies of the hotspot area, the P-wave model is quite consistent with the magnetic data: at shallow (<400 km) depths, the zone of the lowest velocities is also concentrated under the Main Ethiopian Rift. [ABSTRACT FROM AUTHOR]

The spatial distribution of the satellite lithospheric magnetic field is analyzed as a parameter associated with plume magmatism processes that occurred on the territories of large igneous magmatic provinces (LIPs). We consider the lithospheric geomagnetic field at an altitude of ~250–300 km derived from the CHAMP satellite data for three LIPs of different ages: Central European, North Atlantic, and Siberian. The results are evidence that the parameters of the lithospheric geomagnetic field are controlled by complex magmatic processes. Ancient mantle plumes are reflected in the lithospheric magnetic field as conformal positive anomalies of large magnitudes, while the lithospheric magnetic field on the territory of the young North Atlantic province is significantly reduced. Therefore, the data from geomagnetic satellite surveys add valuable information to the available geological and geophysical data and should be used holistically for studying the crustal heterogeneity of LIPs. [ABSTRACT FROM AUTHOR]

The distribution of the lithospheric magnetic anomalies over the territory of the Tibetan Himalayan highlands, the Western and Eastern Himalayan syntaxes, and part of the Hindustan Peninsula, obtained from measurements on the German Earth satellite CHAMP (Challenging Minisatellite Payload) in different years of its mission, is studied. The lithospheric magnetic anomalies maps for the modulus of the full vector Ta and for the horizontal component Xa at different satellite flight levels are presented. The accordance of lithospheric magnetic anomalies maps to the regional geological and tectonic data and regional geophysics is considered. The anomalous magnetic field sign inversion over the northern part of the Indian Plate is explained as a possible effect of mantle heating, the rise of the Curie isotherm, and the loss of the initial magnetization of the earth's lower crust. A series of split-level maps of magnetic anomalies are compared with each other, and the degree of their similarity is estimated. To illustrate the expediency of separation lithospheric magnetic anomalies directly from satellite measurements and to demonstrate the difference between maps of regional lithospheric and near-surface anomalies, a Ta map was constructed based on the data from the EMAG2 database of the WDMAM model at a 4 km level. The results of the work show that the identified magnetic anomalies over the Indo-Asian collision region are adequately consistent with the existing regional geological, tectonic, and geophysical conditions. [ABSTRACT FROM AUTHOR]

The results of studying the structural features of an anomalous magnetic field and modeling sources in the Earth's crust of the Middle Ural region are presented. A territory of 880 × 500 km2 covers the eastern part of the East European Platform, the Middle Urals, and the western part of the West Siberian Plate. Within this area, intense linear anomalies are observed in the anomalous magnetic field in the Urals and Western Siberia, and large regional anomalies are identified within the East European Platform. The interpretation of airborne magnetic data was conducted using original parallel algorithms for separating magnetic field sources by depth and solving the structural inverse problem of magnetometry. As a result, a model of magnetic field sources in the layers of the Earth's crust of the region under study was constructed for various values of magnetization. [ABSTRACT FROM AUTHOR]

The results of numerical modeling and experimental investigation of the possibilities of using simultaneous magnetization of a tested ferromagnetic product by strong constant and weak alternating fields are presented to determine the possibility of increasing the reliability of magnetic flaw detection of gas pipelines, especially for detecting stress-corrosion damage. The previously revealed occurrence of a local anomaly in the magnetic permeability of the product material correlating with the parameters of the underlying continuity defect in the presence of a strong permanent magnetic field on the defect-free side of the test object has been confirmed. As a result, the magnetic flux leakage (MFL) method, widely used for flaw detection of main gas pipelines, can in principle be supplemented by the use of an attached eddy current transducer to detect this local anomaly of magnetic permeability. This transducer can be used instead of (or in combination with) the permanent tangential magnetic field sensor commonly used in the MFL method. No advantages of such a replacement have been revealed. There were also no possibilities for detecting stress-corrosion damage by local changes in electrical conductivity at the location of the defect and no possibilities for using the SLOFEC method in the monitoring of main gas pipelines due to unacceptably high energy consumption. [ABSTRACT FROM AUTHOR]

Solar wind ion sputtering is one of several non‐negligible loss mechanisms for water ice in permanently shadowed regions (PSRs) near the lunar poles. Previous estimates of the solar wind ion flux within south polar PSRs have considered only the ambient solar wind flow and effects of topography. Here, improved maps of crustal magnetic fields in the lunar polar regions are constructed, confirming that more anomalies are present near the south pole than near the north pole. These anomalies have moderate amplitudes, occur over at least two permanently shadowed craters, and correlate approximately with the exposed water ice distribution. Because of the low angle of solar wind incidence near the poles, these anomalies are likely effective in reducing the ion flux, and any resulting water ice loss rate. These anomalies may therefore explain why more water ice is found near the south pole than near the north pole. Plain Language Summary: Significant amounts of water ice are believed to be trapped in permanently shadowed regions (PSRs) near the lunar south pole. The extent to which water ice can survive in PSRs is limited by several factors, including the rate of sputtering losses from the solar wind ion bombardment. This loss rate has previously been estimated considering only the ambient solar wind flow and effects of topography. However, due to the low angle of solar wind incidence near the poles, even moderate magnetic anomalies may strongly deflect the ion bombardment within PSRs, helping to shield their interiors from ion sputtering losses. Here, new maps of crustal fields in the lunar polar regions are presented, confirming that more strong anomalies are present near the south pole than near the north pole, including over at least two permanently shadowed craters. These anomalies are about one‐quarter of the strength of the prototypical Reiner Gamma anomaly on the near side and should therefore be effective in shielding the interiors of these PSRs from the ion bombardment. The presence of stronger anomalies near the south pole than near the north pole may therefore help explain why more water ice is found near the south pole. Key Points: Moderately strong magnetic anomalies are present near the lunar south pole and correlate approximately with the ice exposure distributionThese anomalies are likely effective in reducing the solar wind ion flux and resulting water ice loss rate in permanently shadowed regionsThe presence of stronger anomalies over the south polar region than the north polar region may explain why more water ice is found there [ABSTRACT FROM AUTHOR]

The circumlunar environment is a dusty plasma consisting of small particles of lunar regolith, photoelectrons, electrons, and solar wind ions. When moving around the Earth, part of the trajectory of the Moon passes through the Earth's magnetosphere. In addition, the magnetic field is characteristic for some areas on the Moon, the so-called lunar magnetic anomalies. The magnetic field values above these areas can exceed the magnetic field values of the Earth's magnetosphere in the region of the Moon's trajectory by one or two orders of magnitude. The magnetic field and photoelectron density gradients can lead to the development of drift turbulence. The relevant conditions are discussed in this work. [ABSTRACT FROM AUTHOR]

Based on analysis of anomalous magnetic and gravity fields, magnetic (to a depth of 18 km) and density (to a depth of 35 km) depth models were calculated for the Malmyzh and Poni–Mulino gold–copper–porphyry ore clusters located in the northern part of the Middle Amur sedimentary basin. A ring structure of magmatogenic origin has been distinguished, which determines the spatial location of mineralization in the Malmyzh and Poni–Mulino ore clusters. This structure can be considered as a promising area for searching for gold–copper–porphyry ore mineralization. In addition, a number of promising areas associated with granitoid and diorite intrusions developed along the periphery of the ring structure can be identified. Some of these intrusions are under the Amur River and are overlain by the sedimentary cover of the Middle Amur sedimentary basin. The calculated geophysical depth model for the Malmyzh ore cluster is consistent with the petrological models of giant Cu-porphyry deposits. [ABSTRACT FROM AUTHOR]

The current work makes use of the geometrical configuration of the two lower-altitude Swarm satellites (Swarm A and C), moving side by side with a longitudinal distance of 1.4°, to estimate a two-dimensional (2D) model of the lithospheric magnetic anomaly field over Egypt using gradient data. The gradient in both the north–south and the east–west directions have been inverted using the weighted damping least-squares fit technique to estimate the best model coefficients of the 2D model. The best model coefficients have been obtained under the expansion of the Legendre polynomial from degree n = 7 to n = 56. Results showed that the gradient of the field in the north–south direction is always much smoother than that in the east–west direction. The noise in the east–west direction is attributed to the different environmental conditions surrounding both satellites. The modeled field always showed smoother variations than the observed data, even for the horizontal components (Bx and By). [ABSTRACT FROM AUTHOR]

The paper analyzes the "bright spot" and "flat spot" anomalies of seismic data on the southeastern flank of the Knipovich Ridge associated with the accumulation of free gas in the sedimentary cover above the oceanic basement. The identified anomalies are associated spatially with negative values of the residual Bouguer anomaly and positive magnetic field (ΔТа) anomalies. This fact indicates the existence of decompaction zones in the crust and upper mantle related to serpentinization that can also provoke the superimposed, probably modern, chemogenic magnetization and distortion of the primary linear pattern of magnetic anomalies in the oceanic basement in the study area. Serpentinization was also responsible for vertical displacements of the crustal and upper mantle blocks on the flanks, leading to deformations of the sedimentary cover with the rock dilation. Off-axis seismicity indicates tectonic disruptions on flanks of the ridge with a higher access of water necessary for the serpentinization and the subsequent change in the physical properties of rocks reflected in geophysical fields. The eastern flank of the Knipovich Ridge underwent tectonic activation along the basement structures representing the northern extension of the Senja fracture zone, resulting in accumulations of free gas in the sedimentary cover. [ABSTRACT FROM AUTHOR]

Magnetization is a natural property of magnetic materials which is widely used to analyze paramagnetic data, locate unexploded ordnance, explore mineral deposits and gas resources, and image anomalous magnetic structures in the Earth's crust. An essential and challenging task is to compute accurate magnetic anomalies caused by realistic magnetic 3D structures. In this study, for the first time, we derive the analytical expressions of magnetic potential, magnetic field and magnetic gradient tensor for magnetic materials with 3D polyhedral shapes and magnetization vectors that may vary in the space following polynomial trends. The order of polynomials can vary from one to high positive integers in both horizontal and vertical directions. Synthetic and realistic deposit models are used to validate our analytical solutions. We release the open‐source code in C++. Plain Language Summary: The geophysical magnetic exploration method is widely applied in the exploration of mineral deposits and gas resources, studies of sea‐floor spreading, detection of military and civilian magnetic objects, and Earth crust and other planets imaging. To interpret anomalous magnetic data acquired by ground, airborne, borehole, marine, and satellite magnetic surveys, geophysicists need to accurately compute the magnetic field and magnetic gradient tensor field of 3D magnetic structures with realistic magnetization. In this study, we successfully derive a set of closed‐form solutions of magnetic field and magnetic gradient tensor for 3D polyhedral structures with magnetization vectors which may vary in the space according to polynomial laws of arbitrary order. The intensity of magnetization can also vary in both horizontal and vertical directions. Based on the fact that 3D polyhedral bodies can well approximate arbitrary geometries of realistic structures and polynomial magnetization variations can well represent arbitrary distributions of magnetization, our closed‐form solutions could accurately compute the magnetic field and magnetic gradient tensor caused by realistic geological rocks and would play an essential role in the magnetic exploration method. Key Points: Closed‐form solutions of magnetic field and magnetic gradient tensor are derived for 3D polyhedral structures with complicated magnetizationThe magnetization in polyhedrons can vary in both horizontal and vertical directionsOpen source C++ software is free to use [ABSTRACT FROM AUTHOR]

The volcanic structure of the Seymour Sewell seamount appears to have formed over a relatively long time in at least two stages. Its main massif was formed as a result of volcanic activity in the axial zone of the Central Indian Ridge about 16.3 Ma ago for about 0.5 Ma. Then the volcanic process temporarily stopped and the seamount drifted 260 km southwest along with the supporting African plate. In the last epoch of direct magnetic polarity (Brunes, 680 ka ago), as a result of a new cycle of volcanotectonic activity, the southeastern segment of the seamount collapsed. At this time, a new portion of magmatic material with a high ferrous mineral content was erupted here, reflected in the more intense magnetic anomaly confined to this part of the seamount. [ABSTRACT FROM AUTHOR]

Despite the prevalence of well-established and explored navigation systems, alternative localization methods are currently the focus of intensive research. This interest is driven by geopolitical challenges and increasingly sophisticated applications of mobile robots and uncrewed aerial vehicles. This study investigates the problem of real-time positioning in GPS-denied environments. Based on the mapped magnetic anomaly field and using Bayesian formalism for data fusion, the localization obtained from embedded sensors is corrected to reduce cumulative errors. The proposed method has minimal computational cost and a minimal number of tunable parameters. The paper introduces it and demonstrates its effectiveness in a laboratory study. Experimental tests, using a system equipped with an Inertial Measurement Unit, demonstrated a significant reduction in localization uncertainty. The improvement was especially notable in areas with large, smooth variations in the magnetic field. Finally, the accuracy of the method is analyzed, and its performance is compared to a particle filter. • The paper proposes a framework for a magnetic navigation module. • The module utilizes local anomalies of the magnetic field. • In GPS-denied environments, magnetic corrections improve the IMU-based localization. • When the reference position is available, the module maps the magnetic anomaly field. • A lab-scale verification and a comparison to the particle filter are provided. [ABSTRACT FROM AUTHOR]