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Copyright of Reviews of Geophysics & Planetary Physics is the property of Editorial Office of Reviews of Geophysics & Planetary Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

(Top) Variation of the earth's magnetic inclination along with diverse geographical locations of representative events. (bottom) The interaction between the earth's magnetic inclination and acoustic pulse generated from the events. Note that the events that occurred in the mid-latitudes of the southern and northern hemispheres show strong single-beam directivity, whereas the events situated in the polar and equatorial regions show omni-directional and dual-beam directivity. [Display omitted] Influence of the geomagnetic field on ionospheric disturbances associated with acoustic waves has been widely reported and unanimously agreed upon for the mid-latitude north and mid-latitude south regions, while elaborate studies in this regard are scarce for the polar and equatorial regions. In this study, we present a holistic overview that characterizes the ionospheric directivity from a global perspective considering observations from various natural case studies and anthropogenic phenomena and compare the results with the numerically simulated TEC anomaly. Our focused approach highlights that ionospheric directivity is omnidirectional and bidirectional (or dual-beam) for magnetically polar and equatorial regions, respectively. The mid-latitude north and south domains were also looked upon where the ionospheric directivity is strongly unidirectional (or single-beam). Further, the results of our numerical simulation model appear to complement well with the observations. [ABSTRACT FROM AUTHOR]

В статье описана геомагнитная компонента системы «Аврора», выполняющая оценку состояния магнитного поля Земли по данным станций «Паратунка» (Камчатский край, 52.97∘ N, 158.24∘ E) и «Хабаровск» (47.61∘ N, 134.69∘ E). Данные получены путем прямых измерений на магнитных обсерваториях. Геомагнитная компонента системы «Аврора» разработана в ИКИР ДВО РАН. Функции данной компоненты базируются на новых подходах и методах, построенных коллективом ученых лаборатории Системного анализа. Разработанные методы основаны на синтезе элементов теории вейвлет-преобразования с методами теории вероятностей и математической статистики. Система обеспечивает комплексную оценку состояния магнитного поля Земли в возмущенные и спокойные периоды и дает возможность изучать пространственно-временные особенности и динамику процессов в магнитосфере Земли. Заключение о состоянии магнитного поля формируется в оперативном режиме. Анализ работы системы в периоды рассмотренных в статье событий подтвердил возможность возникновения слабых короткопериодных синхронных геомагнитных возмущений, предшествующих началу магнитных бурь. Рассмотренная в статье геомагнитная компонента дополняет комплексный анализ данных геофизического мониторинга в системе и является важнейшей её частью. Результаты геомагнитной компоненты системы «Аврора» могут быть использованы в качестве дополнительного инструмента в задачах оперативного прогноза космической погоды.

In recent years, geomagnetic observation stations have been subjected to more and more serious interference by HVDC transmission, subway, vehicles, etc. About 35 of the national geomagnetic second sampling stations have been subjected to vehicle interference, which has affected the integrity and efficiency of geomagnetic observation data. In this paper, three GM4 fluxgate magnetometers are used to carry out field interference tests on different types of vehicles in different directions, at different distances and at different speeds at Hongshan geomagnetic station, and the quantitative changes of horizontal component H, vertical component Z and magnetic declination angle D of geomagnetic field are analyzed. The results show that the dynamic vehicle driving orientation can be determined by the variation pattern of geomagnetic declination D component, and the influence of dynamic vehicle speed on geomagnetic field is small in space. A mathematical model of vehicle position change in geomagnetic field is established. Three fluxgate magnetometers can be used to invert the vehicle driving direction, driving speed and relative observation instrument position changes caused by geomagnetic stations. It provides a reference for the geomagnetic station to identify the impact of vehicle interference.

After 50 years of research on the correlation between the geomagnetic field and climate, we have gained a deeper understanding that the regulation of climate by geomagnetic field changes is far more complex than previously imagined. In this paper, we comprehensively review the research connecting the geomagnetic field and climate over the past 50 years, examining different spatial and temporal scales. Our results demonstrate a significant correlation between geomagnetic field changes and climate at various scales, including millennial-scale geomagnetic reversals, thousand-year-scale geomagnetic shifts, centennial-scale geomagnetic abrupt, and even decadal-scale variations in geomagnetic activity. The Matuyama–Brunhes geomagnetic reversal is associated with the cold climate. The increase in galactic cosmic rays (GCR) during this period gave rise to the formation of low-altitude cloud "umbrella effects", subsequently weakening the East Asian summer monsoon and intensifying the East Asian winter monsoon. Archaeomagnetic data from Mesopotamia remarkably illustrates a consistent correlation between four cold periods in the last three thousand years and a sudden increase in geomagnetic anomalies. Exploring the possibility that these geomagnetic anomalies correspond to extreme tilts of the Earth's dipole, it is hypothesized that auroral ovals and sub-auroral regions may have expanded to lower latitudes. In these regions, cosmic rays potentially interacted with a more humid troposphere, resulting in increased cloud cover and, consequently, observed atmospheric cooling. Changes in GCR flux, induced by solar activity and variations in the geomagnetic field, are proposed to have significant implications for alterations in temperate pressure systems, precipitation patterns, and atmospheric electric fields. These effects play diverse roles within the intricately coupled system of the Earth's atmosphere and the near-Earth space environment. However, it's important to note that correlation does not imply causation, and the potential mechanisms by which the geomagnetic field influences climate change are still a subject of debate. The cosmic ray-cloud mechanism is the most promising avenue for understanding how the geomagnetic field regulates climate, operating effectively across different time scales, but its exact physical mechanisms and relative importance remain unresolved issues. We propose that understanding the correlation between the geomagnetic field and climate from the perspective of solar-terrestrial multisphere coupling is crucial, with a specific focus on the response of regional climate systems to changes in regional magnetic fields. By integrating knowledge from ancient times to the present, from regional to global perspectives, we aim to form a comprehensive understanding of the correlation between the geomagnetic field and climate change. The recent successful launch of Aoke-1, which can delicately characterize magnetic field changes in the South Atlantic Anomaly (SAA), the first discovery of the centennial-scale western Pacific anomaly (WPA), and the rapid development of paleomagnetic/archaeomagnetic and paleoclimate data reconstruction have provided new historical opportunities for research on the geomagnetic field and climate. This progress indicates that the study of the impact of geomagnetic field changes on climate will be propelled to new heights.

Low Earth orbit (LEO) satellites have emerged as a primary tool for global geomagnetic field detection and model refinement, owing to their wide coverage, high resolution, and absence of geographical limitations. This paper provides a comprehensive review of the history, key characteristics, measurement accuracy, and future trends in LEO satellite magnetic field measurements. The first part of the paper outlines the evolution of LEO satellites, highlighting their unique advantages. The focus then shifts to the calibration methodology for in-orbit LEO satellite magnetic measurements, with a specific emphasis on vector magnetic field intrinsic calibration and alignment algorithms. Calibration results are presented to demonstrate the effectiveness of these methodologies. In the third section, the paper introduces the theory behind global geomagnetic field modeling. An overview of current global geomagnetic field models is provided, encompassing their sources, spatial resolutions, and other relevant attributes. The paper concludes by presenting the global morphology and features of the main field, lithospheric field, magnetospheric, and ionospheric field. Despite the significant progress enabled by LEO satellite technology, global geomagnetic field modeling faces challenges such as limited spatio-temporal resolution. To address this, incorporating near-surface observation data and continuously optimizing modeling technology are deemed essential solutions.

Abstract The navigational accuracy of sea animals and trans-ocean birds provides inspiration in using geo-magnetic field (GMF) for realizing strategic truly autonomous underwater vehicles (AUV) capable of determining their absolute position on earth, without the aid of ship-referenced acoustic baseline systems. Supervised Machine Learning algorithms are applied on the GMF intensity data obtained from NOAA World Magnetic Model for a 900 km2 within the Indian mineral exploratory area in the Central Indian Ocean, with a resolution of 50 m, considering the sensitivity of commercially available magnetometers. It is identified that, for AUVs equipped with magnetometers with a detection sensitivity of 0.1 nT, the supervisory random forest regression and decision tree algorithm trained with priori GMF data, could provide trajectory guidance to AUVs with an absolute mean position accuracy in 2D plane, with reference to the last known position from Integrated Navigation system aided initially with GPS and with acoustic positioning in underwater. Circular Error Probable (CEP 50) of 53 m and 56 m, respectively. The scalar GMF anomaly navigation demonstrated to be a viable GPS-alternative navigation system could be extended to larger areas with inclination and declination vectors, as unique identifiers.

The navigational accuracy of sea animals and trans-ocean birds provides inspiration in using geo-magnetic field (GMF) for realizing strategic truly autonomous underwater vehicles (AUV) capable of determining their absolute position on earth, without the aid of ship-referenced acoustic baseline systems. Supervised Machine Learning algorithms are applied on the GMF intensity data obtained from NOAA World Magnetic Model for a 900 km2 within the Indian mineral exploratory area in the Central Indian Ocean, with a resolution of 50 m, considering the sensitivity of commercially available magnetometers. It is identified that, for AUVs equipped with magnetometers with a detection sensitivity of 0.1 nT, the supervisory random forest regression and decision tree algorithm trained with priori GMF data, could provide trajectory guidance to AUVs with an absolute mean position accuracy in 2D plane, with reference to the last known position from Integrated Navigation system aided initially with GPS and with acoustic positioning in underwater. Circular Error Probable (CEP 50) of 53 m and 56 m, respectively. The scalar GMF anomaly navigation demonstrated to be a viable GPS-alternative navigation system could be extended to larger areas with inclination and declination vectors, as unique identifiers. [ABSTRACT FROM AUTHOR]

Solar particle events (SPEs) are short-lived bursts of high-energy particles from the solar atmosphere and are widely recognized as posing significant economic risks to modern society. Most SPEs are relatively weak and have minor impacts on the Earth's environment, but historic records contain much stronger SPEs which have the potential to alter atmospheric chemistry, impacting climate and biological life. The impacts of such strong SPEs would be far more severe when the Earth's protective geomagnetic field is weak, such as during past geomagnetic excursions or reversals. Here, we model the impacts of an extreme SPE under different geomagnetic field strengths, focusing on changes in atmospheric chemistry and surface radiation using the atmosphere-ocean-chemistry-climate model SOCOL3-MPIOM and the radiation transfer model LibRadtran. Under current geomagnetic conditions, an extreme SPE would increase NOx concentrations in the polar stratosphere and mesosphere, causing reductions in extratropical stratospheric ozone lasting for about a year. In contrast, with no geomagnetic field, there would be a substantial increase in NOx throughout the entire atmosphere, resulting in severe stratospheric ozone depletion for several years. The resulting ground-level ultraviolet (UV) radiation would remain elevated for up to 6 y, leading to increases in UV index up to 20 to 25% and solar-induced DNA damage rates by 40 to 50%. The potential evolutionary impacts of past extreme SPEs remain an important question, while the risks they pose to human health in modern conditions continue to be underestimated. [ABSTRACT FROM AUTHOR]

It is very important to carry out effective safety inspections on suppression rigging because of the bad service environment of suppression rigging: marine environments. In this paper, the multi-parameter simulation method in ANSYS and ANSYS Electronics Suite simulation software is used to simulate the effect of geomagnetic fields on the magnetic induction intensity of defective pressed rigging under the variable stress in marine environments. The results of the ANSYS simulation and geomagnetic flaw detection equipment are verified. The simulation results show that, according to the multi-parameter simulation results of ANSYS and ANSYS Electronics Suite simulation software, it can be found that, under the action of transverse force, the internal stress of the pressed rigging will affect the magnetic field around pressed rigging with defects. With an increase in internal stress in the range of 0~20 MPa, the magnetic induction intensity increases to 0.55 A/m, and with an increase in internal stress in the range of 20~150 MPa, the magnetic induction intensity decreases to 0.06 A/m. From the use of a force magnetic coupling analysis method, it can be obtained, under the lateral force of the defects in suppressing rigging, that magnetic flux leakage signals decrease with an increase in the rigging's radial distance. The experiment results show that the difference between the peak and trough of the magnetic induction intensity at the pressed rigging defect calculated by the ANSYS simulation is very consistent with the results measured by the geomagnetic flaw detection equipment. [ABSTRACT FROM AUTHOR]

The Earth’s abundance of iron has played a crucial role in both generating its geomagnetic field and contributing to the development of early life. In ancient oceans, iron ions, particularly around deep-sea hydrothermal vents, might have catalyzed the formation of macromolecules, leading to the emergence of life and the Last Universal Common Ancestor. Iron continued to influence catalysis, metabolism, and molecular evolution, resulting in the creation of magnetosome gene clusters in magnetotactic bacteria, which enabled these unicellular organisms to detect geomagnetic field. Although humans lack a clearly identified organ for geomagnetic sensing, many life forms have adapted to geomagnetic field—even in deep-sea environments—through mechanisms beyond the conventional five senses. Research indicates that zebrafish hindbrains are sensitive to magnetic fields, the semicircular canals of pigeons respond to weak potential changes through electromagnetic induction, and human brainwaves respond to magnetic fields in darkness. This suggests that the trigeminal brainstem nucleus and vestibular nuclei, which integrate multimodal magnetic information, might play a role in geomagnetic processing. From iron-based metabolic systems to magnetic sensing in neurons, the evolution of life reflects ongoing adaptation to geomagnetic field. However, since magnetite-activated, torque-based ion channels within cell membranes have not yet been identified, specialized sensory structures like the semicircular canals might still be necessary for detecting geomagnetic orientation. This mini-review explores the evolution of life from Earth’s formation to light-independent human magnetoreception, examining both the magnetite hypothesis and the electromagnetic induction hypothesis as potential mechanisms for human geomagnetic detection.

Abstract Machine learning (ML) as a tool is rapidly emerging in various branches of contemporary geophysical research. To date, however, rarely has it been applied specifically for the study of Earth’s internal magnetic field and the geodynamo. Prevailing methods currently used in inferring the characteristic properties and the probable time evolution of the geodynamo are mostly based on reduced representations of magnetohydrodynamics (MHD). This study introduces a new inference method, referred to as Current Loop-based UNet Model Segmentation Inference (CLUMSI). Its long-term goal focuses on uncovering concentrations of electric current densities inside the core as the direct sources of the magnetic field itself, rather than computing the fluid motion using MHD. CLUMSI relies on simplified models in which equivalent current loops represent electric current systems emerging in turbulent geodynamo simulations. Various configurations of such loop models are utilized to produce synthetic magnetic field and secular variation (SV) maps computed at the core–mantle boundary (CMB). The resulting maps are then presented as training samples to an image-processing neural network designed specifically for solving image segmentation problems. This network essentially learns to infer the parameters and configuration of the loops in each model based on the corresponding CMB maps. In addition, with the help of the Domain Adversarial Training of Neural Networks (DANN) method during training, historical geomagnetic field data could also be considered alongside the synthetic samples. This implementation can increase the likelihood that a network trained primarily on synthetic data will appropriately handle real inputs. Our results focus mainly on the method's feasibility when applied to synthetic data and the quality of these inferences. A single evaluation of the trained network can recover the overall distribution of loop parameters with reasonable accuracy. To better represent conditions in the outer core, the study also proposes a computationally feasible process to account for magnetic diffusion and the corresponding induced currents in the loop models. However, the quality of the reconstruction of magnetic field properties is compromised by occasional poor inferences, and an inability to recover realistic SV. Graphical Abstract

Living organisms have evolved within the natural electromagnetic fields (EMFs) of the earth which comprise the global atmospheric electrical circuit, Schumann resonances (SRs) and the geomagnetic field. Research suggests that the circadian rhythm, which controls several physiological functions in the human body, can be influenced by light but also by the earth's EMFs. Cyclic solar disturbances, including sunspots and seasonal weakening of the geomagnetic field, can affect human health, possibly by disrupting the circadian rhythm and downstream physiological functions. Severe disruption of the circadian rhythm increases inflammation which can induce fatigue, fever and flu-like symptoms in a fraction of the population and worsen existing symptoms in old and diseased individuals, leading to periodic spikes of infectious and chronic diseases. Possible mechanisms underlying sensing of the earth's EMFs involve entrainment via electrons and electromagnetic waves, light-dependent radical pair formation in retina cryptochromes, and paramagnetic magnetite nanoparticles. Factors such as electromagnetic pollution from wireless devices, base antennas and low orbit internet satellites, shielding by non-conductive materials used in shoes and buildings, and local geomagnetic anomalies may also affect sensing of the earth's EMFs by the human body and contribute to circadian rhythm disruption and disease development.

Machine learning (ML) as a tool is rapidly emerging in various branches of contemporary geophysical research. To date, however, rarely has it been applied specifically for the study of Earth's internal magnetic field and the geodynamo. Prevailing methods currently used in inferring the characteristic properties and the probable time evolution of the geodynamo are mostly based on reduced representations of magnetohydrodynamics (MHD). This study introduces a new inference method, referred to as Current Loop-based UNet Model Segmentation Inference (CLUMSI). Its long-term goal focuses on uncovering concentrations of electric current densities inside the core as the direct sources of the magnetic field itself, rather than computing the fluid motion using MHD. CLUMSI relies on simplified models in which equivalent current loops represent electric current systems emerging in turbulent geodynamo simulations. Various configurations of such loop models are utilized to produce synthetic magnetic field and secular variation (SV) maps computed at the core–mantle boundary (CMB). The resulting maps are then presented as training samples to an image-processing neural network designed specifically for solving image segmentation problems. This network essentially learns to infer the parameters and configuration of the loops in each model based on the corresponding CMB maps. In addition, with the help of the Domain Adversarial Training of Neural Networks (DANN) method during training, historical geomagnetic field data could also be considered alongside the synthetic samples. This implementation can increase the likelihood that a network trained primarily on synthetic data will appropriately handle real inputs. Our results focus mainly on the method's feasibility when applied to synthetic data and the quality of these inferences. A single evaluation of the trained network can recover the overall distribution of loop parameters with reasonable accuracy. To better represent conditions in the outer core, the study also proposes a computationally feasible process to account for magnetic diffusion and the corresponding induced currents in the loop models. However, the quality of the reconstruction of magnetic field properties is compromised by occasional poor inferences, and an inability to recover realistic SV. [ABSTRACT FROM AUTHOR]

A typical magnetometer-based measurement-while-drilling (MWD) system determines the azimuth of the bottom hole assembly during the drilling process by employing triaxial accelerometers and magnetometers. The geomagnetic azimuth solution is susceptible to magnetic interference, especially strong magnetic interference and so a rotary norm constraint filtering (RNCF) method for azimuth estimation, designed to support a gyroscope-aided magnetometer-based MWD system, is proposed. First, a new magnetic dynamical system, one whose output is observed by the magnetometers triad, is designed based on the Coriolis equation of the desired geomagnetic vector. Second, given that the norm of the non-interfered geomagnetic vector can be approximated as a constant during a short-term drilling process, a norm constraint procedure is introduced to the Kalman filter. This is achieved by the normalization of the geomagnetic part of the state vector of the dynamical system and is undertaken in order to obtain a precise geomagnetic component. Simulation and actual drilling experiments show that the proposed RNCF method can effectively improve the azimuth measurement precision with 98.5% over the typical geomagnetic solution and 37.1% over the KF in a RMSE sense when being strong magnetic interference environment. [ABSTRACT FROM AUTHOR]

The disturbances in the lower ionosphere during the strong earthquake in Türkiye and Syria and its strongest aftershock on February 6, 2023, are analyzed using data from ground-based magnetometers. The observation points are located at distances 700 to 1600 km from the epicenter of the seismic event. As a characteristic of the ionospheric response to these events, variations in the magnetic field have been analyzed at the İznik, Grocka, Panagjurishte, and Surlari magnetic observatories. Earthquake epicenter is known to be a source of both seismic Rayleigh waves and atmospheric acoustic-gravity waves. Using the difference in velocities, at which these waves propagate from the epicenter, and their spectral composition, we found the ionospheric responses to the events that are interpreted quite well in terms of acoustic waves (produced by seismic Rayleigh wave) and atmospheric internal gravity waves generated in the earthquake epicenter. [ABSTRACT FROM AUTHOR]

Using the Thermosphere-Ionosphere-Electrodynamic General Circulation Model (TIEGCM), a comparison of the ionospheric total electron content (TEC) between the South Atlantic anomaly (SAA) and the Indian Ocean (IO) at solar maximum is performed in this study. The results show that the average total electron content in the SAA is greater than that in the Indian Ocean in general. In order to further analyze the difference between the two regions, the empirical orthogonal function (EOF) are used to investigate the temporal and spatial characteristics of TEC. The empirical orthogonal function method separate part of the global four-peak structure (an equatorial ionization anomaly structure, distributed in Southeast Asia, South America, Africa, and central Pacific) and spatial variations in both regions. Moreover, the first mode of EOF shows the different distribution of Equatorial ionization anomaly in South America and central Pacific caused by deviation of geomagnetic field and tides between two regions, and the enhancement of TEC in SAA region at dusk is emphasized, but the enhancement of TEC in IO region at dawn is emphasized. The second mode performs the distribution of EIA in Africa related to solar radiation and E χ B drift. The third mode indicates the similar spatiotemporal variations from the geomagnetic field. Besides, the correlation between TEC and Dst in two regions indicate that there are some deficiencies in simulation to the specificity of SAA, and the deficiencies are likely caused by the model's inaccurate simulation of the magnetic field and particle deposition in the SAA region. [ABSTRACT FROM AUTHOR]

This paper represents the equilibrium positions and stability of two artificial satellites connected by light, flexible, and elastic long tethers under the combined effect of several classical perturbative forces in an elliptical orbit. The tether may be conducting or non-conducting. In our problem, it is taken as non-conducting in nature. We have treated the problem by taking five perturbative forces on the system simultaneously. Three perturbations exist due to the influences of the earth, namely geomagnetic fields, shadows, and oblateness. The other perturbations are due to the elasticity of the cable and solar light pressure. The effect of air resistance is neglected, considering the satellites as high-altitude satellites. To determine the stability of the satellites, we have used the Lyapunov method. The dynamical behaviors of the satellites are represented by differential equations. Based on analytical analysis of the differential equations of motion, we get the equilibrium positions of the system concerned in elliptical orbit. Lyapunov method gives the equilibrium position as unstable as expected. [ABSTRACT FROM AUTHOR]

The geomagnetic field is generated by dynamo processes in the Earth's core. This process is supported by the cooling of the planet and the growth of the solid core. It is known that the magnetic field existed long before the appearance of the solid core, although according to available estimates and calculations, this could not have happened. Moreover, according to some models, thermal conductivity in the Earth's core may be three times higher than generally accepted values. In this case, the magnitude of the convective heat flow decreases and the generation of the magnetic field stops. In the above-mentioned models it was assumed that the magnitude of the heat flow at the core – mantle boundary over the entire existence of the Earth linearly decreased by only 15–20 %. The latter is a rough guess. Significantly large changes in heat flow are predicted by models of mantle cooling, in which the growth of convective heat flow in ancient times occurs due to a decrease in the viscosity of the mantle with an increase in the temperature of the substance. Below we consider a model of the cooling of the Earth with a threefold value of the thermal conductivity of the core. It is shown that the use of a combined model of core and mantle cooling makes it possible to significantly increase the heat flow at the core – mantle boundary in ancient times. To slow down the growth of the solid core, a subadiabatic layer is included in the model. As a result, the size of the solid core in the model satisfies seismological observations. The model allows us to obtain a sufficient amount of energy to generate a geomagnetic field, starting from the moment the liquid core appeared and to the present. The appearance of a solid core 2.4 billion years ago, which does not lead to sharp changes in heat flow in the model, is consistent with paleomagnetic observations that do not record changes in the behavior of the magnetic field. The model does not exclude the existence of a multipole magnetic field at the initial stage.

Life on Earth evolved to accommodate the biochemical and biophysical boundary conditions of the planet millions of years ago. The former includes nutrients, water, and the ability to synthesize other needed chemicals. The latter includes the 1 g gravity of the planet, radiation, and the geomagnetic field (GMF) of the planet. How complex life forms have accommodated the GMF is not known in detail, considering that Homo sapiens evolved a neurological system, a neuromuscular system, and a cardiovascular system that developed electromagnetic fields as part of their functioning. Therefore, all of these could be impacted by magnetic fields. In addition, many proteins and physiologic processes utilize iron ions, which exhibit magnetic properties. Thus, complex organisms, such as humans, generate magnetic fields, contain significant quantities of iron ions, and respond to exogenous static and electromagnetic fields. Given the current body of literature, it remains somewhat unclear if Homo sapiens use exogenous magnetic fields to regulate function and what can happen if the boundary condition of the GMF no longer exerts an effect. Proposed deep space flights to destinations such as Mars will provide some insights, as space flight could not have been anticipated by evolution. The results of such space flight “experiments” will provide new insights into the role of magnetic fields on human functioning. This review will discuss the literature regarding the involvement of magnetic fields in various normal and disturbed processes in humans while on Earth and then further discuss potential outcomes when the GMF is no longer present to impact host systems, as well as the limitations in the current knowledge. The GMF has been present throughout evolution, but many details of its role in human functioning remain to be elucidated, and how humans have adapted to such fields in order to develop and retain function remains to be elucidated. Why this understudied area has not received the attention required to elucidate the critical information remains a conundrum for both health professionals and those embarking on space flight. However, proposed deep space flights to destinations such as Mars may provide the environments to test and assess the potential roles of magnetic fields in human functioning.

• Formation of low magnetic field region (dent) in Earth's magnetosphere during intense storm. • Altitude and mirror points of charged particles get affected by magnetic field hump and dent. • The dent in magnetic field is formed closer to the Earth as strength of ring current increases. The development of the ring current through a westward circulation of energetic ions around the Earth in the low latitude region during geomagnetic storms has been known to us for the past several decades. The symmetric part of the ring current exists in the form of a ring around the Earth at a distance of ≈ 3–7 R e from the center of the Earth. The location and strength of the ring current is mainly controlled by the interplanetary solar wind conditions. The presence of such external current forms the additional mini magnetic dipole in the vicinity of the Earth's space, which eventually affects the geomagnetic field configuration. The magnetic field produced due to the ring current opposes the geomagnetic field inside and adds to the geomagnetic field outside the location of the ring current. This scenario has been modelled in this paper by using a circular loop of uniform current around the Earth to represent the ring current flow around the Earth. The aim of the present study is to understand the overall changes in the magnetic field and its influence on the radiation belt energetic (MeV range) electrons and protons during a geomagnetic storm. The model calculations suggest the formation of low and high magnetic field regions (here referred to as dent and hump) in the Earth's magnetosphere due to intense westward ring current. The size and position of these low and high magnetic field regions are controlled by the strength and location of the ring current. It is found that both the altitudinal reach and mirror point of the bouncing-drifting radiation belt energetic particles are significantly affected by the presence of the dent and the hump in the magnetic field driven by the ring current. The decrease in ground magnetic field of 1700 nT or more, which is similar to the geomagnetic field variation observed during the historic Carrington event, is possible with the peak ring current strength of 20–30 MA situated at a distance of 2 R e or less from the center of the Earth. [ABSTRACT FROM AUTHOR]

Life on Earth evolved to accommodate the biochemical and biophysical boundary conditions of the planet millions of years ago. The former includes nutrients, water, and the ability to synthesize other needed chemicals. The latter includes the 1 g gravity of the planet, radiation, and the geomagnetic field (GMF) of the planet. How complex life forms have accommodated the GMF is not known in detail, considering that Homo sapiens evolved a neurological system, a neuromuscular system, and a cardiovascular system that developed electromagnetic fields as part of their functioning. Therefore, all of these could be impacted by magnetic fields. In addition, many proteins and physiologic processes utilize iron ions, which exhibit magnetic properties. Thus, complex organisms, such as humans, generate magnetic fields, contain significant quantities of iron ions, and respond to exogenous static and electromagnetic fields. Given the current body of literature, it remains somewhat unclear if Homo sapiens use exogenous magnetic fields to regulate function and what can happen if the boundary condition of the GMF no longer exerts an effect. Proposed deep space flights to destinations such as Mars will provide some insights, as space flight could not have been anticipated by evolution. The results of such space flight "experiments" will provide new insights into the role of magnetic fields on human functioning. This review will discuss the literature regarding the involvement of magnetic fields in various normal and disturbed processes in humans while on Earth and then further discuss potential outcomes when the GMF is no longer present to impact host systems, as well as the limitations in the current knowledge. The GMF has been present throughout evolution, but many details of its role in human functioning remain to be elucidated, and how humans have adapted to such fields in order to develop and retain function remains to be elucidated. Why this understudied area has not received the attention required to elucidate the critical information remains a conundrum for both health professionals and those embarking on space flight. However, proposed deep space flights to destinations such as Mars may provide the environments to test and assess the potential roles of magnetic fields in human functioning. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of human heart-rate synchronization with variations in the geomagnetic field (GMF) ("biogeophysical synchronization effect"). We analyzed 403 electrocardiogram (ECG) recordings of 100 or 120 min that were obtained in 2012–2023 from two middle-aged female volunteers in good health. The minute-value series of the GMF vector from the INTERMAGNET network was used. Each ECG recording was individually examined using cross-correlation and wavelet analysis. The findings from two separate experimental sets (306 recordings from Volunteer A and 97 from Volunteer B) displayed notable similarity in all aspects analyzed: (1) For both participants, the biogeophysical synchronization effect is observed in 40–53% of the recordings as a statistically significant (p < 0.0045) correlation between minute heart-rate (HR) time-series values and at least one of the horizontal components of the GMF, with a time shift between values of [−5, +5] min. (2) Wavelet analysis indicates that the spectra of the HR series and at least one GMF component exhibit similarity in 58–61% of cases. (3) The synchronization is most evident within the period range between 8–13 min. The probability of the synchronization effect manifestation was independent of the geomagnetic activity (GMA) level, which was recorded during the observations. [ABSTRACT FROM AUTHOR]

The article describes the sources of geomagnetic data, the reduction of geomagnetic data for the territory of Latvia to the epoch 2021.5, the history of previous magnetic observations in Latvia, the information available in the State Geodetic Network database and the information available in the World Geomagnetism Data Centre. The sequence of absolute measurements is described in detail. To visualise the changes in the magnetic declination value in the territory of Latvia, a 2021.5 year declination fluctuation has been created using ArcGIS Pro. The declination values in Latvia range from 6.68° to 10°, the inclination values range from 71.089° to 72.245° and the total magnetic field values from 51100 nT to 52594 nT. The values obtained for the magnetic field components refer to a magnetically clean environment, and there can be, and are, differences in the natural conditions in the Latvian territory, in natural anomalous locations and in locations with artificially high magnetic field noise (e.g. in cities, near railways, near high voltage lines, etc.). In the Latvian network, points have been selected in locations where the magnetic noise is minimal, as this is the technological process for building such stations. Magnetic observatories are even stricter, so the data coming from the observatories reflect the natural magnetic field without the influence of magnetic anomalies. The reduced magnetic field values and their representation on a map can be used for aeronautical navigation, military applications, identification of local magnetic anomaly sites or search for magnetically clean environments. [ABSTRACT FROM AUTHOR]

The use of a magnetic compass in paleomagnetic studies of highly magnetic rocks (for instance, basalts) can lead to large errors in the orientation of paleomagnetic samples. On the other hand, alternative methods of orientation are relatively time-consuming, and in the case of using a solar compass, they also require sunny weather – a condition that is rarely met, especially when sampling at high and subpolar latitudes. This often leads to the fact that researchers in their work rely on the results of magnetic compass measurements, while assuming that the resulting errors are of a random nature and, with sufficiently good statistics, are averaged. In this study, numerical modeling is performed, which allows us to verify this assumption and assess how much orientation errors associated with the use of a magnetic compass can affect the final results of paleomagnetic studies, such as determining the position of the paleomagnetic pole and the amplitude of ancient geomagnetic variations. As a result of the work performed , it is shown that: 1) the amplitudes of paleosecular variations and the positions of paleomagnetic poles are weakly sensitive to moderate and even relatively large errors in the orientation of paleomagnetic samples associated with the use of a magnetic compass; 2) very large errors in the orientation of samples lead to a significant increase in the within-site scatter of paleomagnetic directions, which makes it possible to detect and exclude the corresponding sites with a large (for instance >15°) value of the α95; 3) the influence of distortions associated with the use of a magnetic compass on the accuracy of determining the position of the paleomagnetic pole and the amplitude of ancient geomagnetic variations depends on latitude. At near-equatorial latitudes, this effect is maximal, at medium latitudes – minimal.

The article describes the sources of geomagnetic data, the reduction of geomagnetic data for the territory of Latvia to the epoch 2021.5, the history of previous magnetic observations in Latvia, the information available in the State Geodetic Network database and the information available in the World Geomagnetism Data Centre. The sequence of absolute measurements is described in detail. To visualise the changes in the magnetic declination value in the territory of Latvia, a 2021.5 year declination fluctuation has been created using ArcGIS Pro. The declination values in Latvia range from 6.68° to 10°, the inclination values range from 71.089° to 72.245° and the total magnetic field values from 51100 nT to 52594 nT. The values obtained for the magnetic field components refer to a magnetically clean environment, and there can be, and are, differences in the natural conditions in the Latvian territory, in natural anomalous locations and in locations with artificially high magnetic field noise (e.g. in cities, near railways, near high voltage lines, etc.). In the Latvian network, points have been selected in locations where the magnetic noise is minimal, as this is the technological process for building such stations. Magnetic observatories are even stricter, so the data coming from the observatories reflect the natural magnetic field without the influence of magnetic anomalies. The reduced magnetic field values and their representation on a map can be used for aeronautical navigation, military applications, identification of local magnetic anomaly sites or search for magnetically clean environments.

The paper aims at an experimental study of the mechanisms of long-distance high-frequency (HF) propagation and spatial and temporal variations of the ionospheric parameters during the first hours of a severe geomagnetic storm of April 23, 2023 by spatially separated measuring equipment located at the research vessel (RV) Noosfera, the Ukrainian Antarctic Akademik Vernadsky station (hereinafter Vernadsky), and the LOFAR observatory PL610 in Borowiec (Poland). High-frequency vertical and oblique sounding techniques of the ionosphere were used. Geospace measurements were carried out synchronously. During the first hours of the geomagnetic storm of April 23–24, 2023, unexpectedly well-correlated variations in the Doppler frequency shifts of HF signals emitted from Vernadsky were observed at the RV Noosfera and the PL610 station. Furthermore, variations in Doppler frequency shifts of HF signals strongly correlate with magnetic field records in Antarctica and Poland. Variations in the frequency of HF signal spectral components, distinguishable during storm conditions, are utilized to clarify the mechanism of long-distance HF propagation and estimate the vertical velocity of ionospheric layers. Signals of HF CHU time radio station (Canada) at 7850 and 14670 kHz were unexpectedly observed in all receiving sites. Most probably, the CHU station radio signals registered during the initial stage of the geomagnetic storm were scattered on the polar ovals’ ionospheric inhomogeneities and propagated further along the return (long arc of the great circle) paths. Redistribution of the ionospheric plasma during the geomagnetic storm leads to the formation of HF radio propagation channels absent under quiet conditions.

It is very important to carry out effective safety inspections on suppression rigging because of the bad service environment of suppression rigging: marine environments. In this paper, the multi-parameter simulation method in ANSYS and ANSYS Electronics Suite simulation software is used to simulate the effect of geomagnetic fields on the magnetic induction intensity of defective pressed rigging under the variable stress in marine environments. The results of the ANSYS simulation and geomagnetic flaw detection equipment are verified. The simulation results show that, according to the multi-parameter simulation results of ANSYS and ANSYS Electronics Suite simulation software, it can be found that, under the action of transverse force, the internal stress of the pressed rigging will affect the magnetic field around pressed rigging with defects. With an increase in internal stress in the range of 0~20 MPa, the magnetic induction intensity increases to 0.55 A/m, and with an increase in internal stress in the range of 20~150 MPa, the magnetic induction intensity decreases to 0.06 A/m. From the use of a force magnetic coupling analysis method, it can be obtained, under the lateral force of the defects in suppressing rigging, that magnetic flux leakage signals decrease with an increase in the rigging’s radial distance. The experiment results show that the difference between the peak and trough of the magnetic induction intensity at the pressed rigging defect calculated by the ANSYS simulation is very consistent with the results measured by the geomagnetic flaw detection equipment.

In the study of the ponderomotive action of Alfvén waves on near-Earth plasma, the general formula for ponderomotive forces, known in classical electrodynamics of continuous media, was previously used. The formula does not explicitly take into account the multi-ion composition of the plasma. Under the action of the waves, significant changes were found in macroscopic parameters — plasma density and velocity. Plasma in Earth’s magnetosphere contains ions with different charge-to-mass ratios. Besides hydrogen and helium ions, the plasma has an admixture of oxygen ions of ionospheric origin, as well as an admixture of other heavy ions. In this connection, a wide range of problems arise on the ponderomotive separation of ions of various types. To solve these problems, it is proposed to use partial ponderomotive forces and to describe the plasma not by hydrodynamic, but by quasi-hydrodynamic equations. In this paper, we discuss the derivation of partial forces for a traveling monochromatic Alfvén wave, and also suggest a method for deriving more general formulas by expanding the classical formula, known in macroscopic electrodynamic, into the sum of partial forces. The ponderomotive separation of ions is illustrated by the example of the problem for diffusion equilibrium of magnetospheric plasma. We propose a hypothesis that Alfvén waves redistribute plasma along geomagnetic field lines in such a way that the plasma at the magnetic field minima is characterized by an increased content of heavy ions. We suggest that a small admixture of heavy ions exists in the polar wind jet stream. The article is dedicated to the 80th anniversary of the discovery of Alfvén waves.

Using the Thermosphere-Ionosphere-Electrodynamic General Circulation Model (TIEGCM), a comparison of the ionospheric total electron content (TEC) between the South Atlantic anomaly (SAA) and the Indian Ocean (IO) at solar maximum is performed in this study. The results show that the average total electron content in the SAA is greater than that in the Indian Ocean in general. In order to further analyze the difference between the two regions, the empirical orthogonal function (EOF) are used to investigate the temporal and spatial characteristics of TEC. The empirical orthogonal function method separate part of the global four-peak structure (an equatorial ionization anomaly structure, distributed in Southeast Asia, South America, Africa, and central Pacific) and spatial variations in both regions. Moreover, the first mode of EOF shows the different distribution of Equatorial ionization anomaly in South America and central Pacific caused by deviation of geomagnetic field and tides between two regions, and the enhancement of TEC in SAA region at dusk is emphasized, but the enhancement of TEC in IO region at dawn is emphasized. The second mode performs the distribution of EIA in Africa related to solar radiation and E×B drift. The third mode indicates the similar spatiotemporal variations from the geomagnetic field. Besides, the correlation between TEC and Dst in two regions indicate that there are some deficiencies in simulation to the specificity of SAA, and the deficiencies are likely caused by the model’s inaccurate simulation of the magnetic field and particle deposition in the SAA region.

Simple Summary: The study of the biological effects of time-varying magnetic fields has attracted more and more attention from researchers, and the number of publications on this topic is growing every year. In this article, we plan to briefly introduce the reader to the results of research, ideas, and discussions on the biological effects of time-varying magnetic fields. This article is illustrated with a large number of generalizing figures and contains a lot of factual data. This review presents the main biological effects observed during magnetic storms and in laboratory studies. The general concepts of studying the influence of magnetic storms on humans are described. Possible approaches to modeling magnetobiological effects at different levels of the organization of living things are presented. The results of the impact of anthropogenic fields on humans (epidemiological studies) are presented. The mechanisms of action of time-varying magnetic fields on living objects are discussed. Dependences of quantitative characteristics of the biological action of time-varying magnetic fields on their frequency, induction, and duration are discussed. The information presented in this manuscript may be valuable for a wide range of readers in the initial assessment of the risks associated with the influence of time-varying magnetic fields on the body. Magnetic fields are a constant and essential part of our environment. The main components of ambient magnetic fields are the constant part of the geomagnetic field, its fluctuations caused by magnetic storms, and man-made magnetic fields. These fields refer to extremely-low-frequency (<1 kHz) magnetic fields (ELF-MFs). Since the 1980s, a huge amount of data has been accumulated on the biological effects of magnetic fields, in particular ELF-MFs. However, a unified picture of the patterns of action of magnetic fields has not been formed. Even though a unified mechanism has not yet been generally accepted, several theories have been proposed. In this review, we attempted to take a new approach to analyzing the quantitative data on the effects of ELF-MFs to identify new potential areas for research. This review provides general descriptions of the main effects of magnetic storms and anthropogenic fields on living organisms (molecular–cellular level and whole organism) and a brief description of the main mechanisms of magnetic field effects on living organisms. This review may be of interest to specialists in the fields of biology, physics, medicine, and other interdisciplinary areas. [ABSTRACT FROM AUTHOR]

Abstract Modern geomagnetic field models are constructed from satellite and observatory data, while models on the millennial timescale are constructed from indirect records of thermoremanent and sedimentary origin. An intermediate period, spanning the last four centuries, is covered by historical survey data and ship-logs, which is strongly dominated by geomagnetic declination information. We apply a sequentialized, Gaussian process-based modeling technique to this dataset and propose a new field model for this era. In order to investigate the information gained from declination records from ship-logs, we separate the dataset and construct a second model, where unpaired declination records (i.e., measurements where only declinations are reported and the rest of the field vector is missing) are removed. The availability of more records helps notably to constrain global field properties like the dipole moment. It also allows to resolve some detailed field structures more accurately. Based on the model constructed from the full dataset, we perform an analysis of the South Atlantic Anomaly and regions of low field intensity in general. We extend a recent analysis of center of mass movement and area evolution of the South Atlantic Anomaly further back in time and confirm the findings of its non-monotonous growth. Graphical Abstract

The paper addresses the problem of attitude stabilization of an artificial Earth satellite with the aid of an electrodynamic control system. Our objective is to stabilize the satellite in a special coordinate system, whose axes are directed along the Lorentz force vector and the geomagnetic induction vector. Thus, natural magneto-velocity coordinate system (NMVCS) is used. We consider the general case of the satellite mass distribution. Therefore, the disturbing action of the gravitation torque is taken into account. The satellite moves along a circular near-Earth orbit. The nonlinear stability analysis based on the Lyapunov direct method is applied in the paper. The proposed approach gives us admissible domains of control parameters for which attitude stabilization in NMVCS is guaranteed without restrictions on the Earth’s magnetic field model. Stabilization conditions are formulated in the form of explicit inequalities for the control parameters. As a result, a control strategy for the satellite attitude stabilization in the NMVCS is elaborated.

A typical magnetometer-based measurement-while-drilling (MWD) system determines the azimuth of the bottom hole assembly during the drilling process by employing triaxial accelerometers and magnetometers. The geomagnetic azimuth solution is susceptible to magnetic interference, especially strong magnetic interference and so a rotary norm constraint filtering (RNCF) method for azimuth estimation, designed to support a gyroscope-aided magnetometer-based MWD system, is proposed. First, a new magnetic dynamical system, one whose output is observed by the magnetometers triad, is designed based on the Coriolis equation of the desired geomagnetic vector. Second, given that the norm of the non-interfered geomagnetic vector can be approximated as a constant during a short-term drilling process, a norm constraint procedure is introduced to the Kalman filter. This is achieved by the normalization of the geomagnetic part of the state vector of the dynamical system and is undertaken in order to obtain a precise geomagnetic component. Simulation and actual drilling experiments show that the proposed RNCF method can effectively improve the azimuth measurement precision with 98.5% over the typical geomagnetic solution and 37.1% over the KF in a RMSE sense when being strong magnetic interference environment.

AbstractThis paper reports three methods of researching the geoelectric index (GEI) based on the ratio between the variation amplitude of geoelectric field on an index calculation day and that on a magnetically quiet day, and uses the three methods to process the observation data of 18 geoelectric stations in China in September 2017. Results showed that, each method has obtained 4096 single-station geoelectric indices D and 240 multi-station average geoelectric indices Ds, all 3-hour indices. Comparing the geoelectric indices with the geomagnetic indices of the 18 stations, it can be understood that: 87.35%–88.26% of indices D are the same with the single-station geomagnetic indices K or have only a difference of 1 from the indices K, and 97.08%–97.50% of indices Ds are the same with the multi-station average geomagnetic indices [Formula: see text] or have only a difference of 1 from the indices [Formula: see text] The high consistency between two kinds of indices shows that the methods of calculating geoelectric index are practicable, and that the calculated indices D and Ds are reliable. The geoelectric field, as an independent observation, should have a criterion to judge the interference.

The geomagnetic field (GMF) is a natural component of the biosphere, and, during evolution, all organisms experienced its presence while some evolved the ability to perceive magnetic fields (MF). We studied the response of 14-3-3 proteins and the plasma membrane (PM) proton pump H+-ATPase to reduced GMF values by lowering the GMF intensity to a near-null magnetic field (NNMF). Seedling morphology, H+-ATPase activity and content, 14-3-3 protein content, binding to PM and phosphorylation, gene expression, and ROS quantification were assessed in maize (Zea mays) dark-grown seedlings. Phytohormone and melatonin quantification were also assessed by LG-MS/MS. Our results suggest that the GMF regulates the PM H+-ATPase, and that NNMF conditions alter the proton pump activity by reducing the binding of 14-3-3 proteins. This effect was associated with both a reduction in H2O2 and downregulation of genes coding for enzymes involved in ROS production and scavenging, as well as calcium homeostasis. These early events were followed by the downregulation of IAA synthesis and gene expression and the increase in both cytokinin and ABA, which were associated with a reduction in root growth. The expression of the homolog of the MagR gene, ZmISCA2, paralleled that of CRY1, suggesting a possible role of ISCA in maize magnetic induction. Interestingly, melatonin, a widespread molecule present in many kingdoms, was increased by the GMF reduction, suggesting a still unknown role of this molecule in magnetoreception. [ABSTRACT FROM AUTHOR]

This paper is focused on study of the geomagnetic field variation response caused by a series of earthquakes with magnitudes of Mw = 7.5–7.8 in Turkey on February 6, 2023. The initial data include high-precision observations of the geomagnetic field with a one-second sampling rate recorded at magnetic observatories in Russia and neighboring countries from middle to high latitudes. The paper analyzes the morphology of the geomagnetic signal, its amplitude-frequency characteristics, pulses in the rate of change and delays of the geomagnetic field response to earthquakes with magnitudes Mw = 7–8 depending on the distance to the source. The results suggest that the geomagnetic effect is detected best in the rate of change recordings, reaching anomalous amplitudes of 10 nT/s. The signal delay ranges from 221 to 592 s depending on the magnetic field component and the distance to the epicenter, which is in the range from 765 to 2650 km for the selected observatories. [ABSTRACT FROM AUTHOR]

Many organisms can sense and respond to magnetic fields (MFs), with migratory species in particular utilizing geomagnetic field information for long-distance migration. Cryptochrome proteins (Crys) along with a highly conserved Iron-sulfur cluster assembly protein (i.e., MagR) have garnered significant attention for their involvement in magnetoresponse (including magnetoreception). However, in vivo investigations of potential transcriptional crosstalk between Crys and MagR genes have been limited. The brown planthopper, Nilaparvata lugens, is a major migratory pest insect and an emerging model for studying MF intensity-related magnetoresponse. Here, we explored in vivo transcriptional crosstalk between Crys (Cry1 and Cry2) and MagR in N. lugens. The expression of Crys and MagR were found to be sensitive to MF intensity changes as small as several micro-teslas. Knocking down MagR expression led to a significant downregulation of Cry1, but not Cry2. The knockdown of either Cry1 or Cry2 individually did not significantly affect MagR expression. However, their double knockdown resulted in significant upregulation of MagR. Our findings clearly indicate transcriptional crosstalk between MagR and Crys known to be involved in magnetoresponse. This work advances the understanding of magnetoresponse signaling and represents a key initial step towards elucidating the functional consequences of these novel in vivo interactions. [ABSTRACT FROM AUTHOR]

Over the past nearly two centuries the magnetic method has been one of the most useful and broadly applied techniques for geologic mapping. Prior to the development of aeromagnetic surveying following World War II magnetic exploration was restricted to ground surveying using primarily mechanical instruments which measured the angular relationships or oscillation of a magnetic needle. This instrumentation was developed initially in western Europe for mapping the geomagnetic field and then iron ore deposits beginning in the seventeenth century. As the instrumentation evolved, sensitivity increased allowing the magnetic method to map additional geologic units of decreasing magnetization. The method was brought to North America where abnormal declination of the magnetic field as measured with the compass was used to map intensely magnetic ironrich rocks in the New Jersey highlands and adjacent New York in the early 1700s. Counterweighted magnetic needles (dip needles) oscillating vertically in the magnetic meridian were developed during the late eighteenth century in Scandinavia for measuring magnetic intensity anomalies that are more readily interpreted than the angular measurements of the compass. These instruments were brought to the eastern United States and were put into use in the mid-1800s in the search for banded iron formations and magnetite-bearing metamorphic and igneous rocks of interest to ore exploration. Similar instrumentation was developed in the British Isles in the first half of the 1800s for national surveys and later for geological exploration. The dip needle and a modification of the sun compass for geologic purposes, the dial compass, were commonly used together for mapping magnetic anomalies of iron ore deposits especially in the Lake Superior region from the U.S. Civil War to World War II. To increase the sensitivity and precision of the measurements numerous additional instruments were developed based on the principle of the dip needle. Particularly important among these were the Schmidt-type magnetometer and Hotchkiss superdip which were widely used in North America after the early 1920s and well into the 1950s. These and similar instruments opened the application of the magnetic method to a broad range of geologic problems important to mineral and petroleum exploration and engineering studies. Interpretation of the mapped magnetic anomalies was advanced with newly developed theoretical representations and model studies of the magnetic intensity of idealized geologic sources that were compared to observed magnetic anomalies. [ABSTRACT FROM AUTHOR]

The paper aims at an experimental study of the mechanisms of long-distance high-frequency (HF) propagation and spatial and temporal variations of the ionospheric parameters during the first hours of a severe geomagnetic storm of April 23, 2023 by spatially separated measuring equipment located at the research vessel (RV) Noosfera, the Ukrainian Antarctic Akademik Vernadsky station (hereinafter Vernadsky), and the LOFAR observatory PL610 in Borowiec (Poland). High-frequency vertical and oblique sounding techniques of the ionosphere were used. Geospace measurements were carried out synchronously. During the first hours of the geomagnetic storm of April 23-24, 2023, unexpectedly well-correlated variations in the Doppler frequency shifts of HF signals emitted from Vernadsky were observed at the RV Noosfera and the PL610 station. Furthermore, variations in Doppler frequency shifts of HF signals strongly correlate with magnetic field records in Antarctica and Poland. Variations in the frequency of HF signal spectral components, distinguishable during storm conditions, are utilized to clarify the mechanism of long-distance HF propagation and estimate the vertical velocity of ionospheric layers. Signals of HF CHU time radio station (Canada) at 7850 and 14670 kHz were unexpectedly observed in all receiving sites. Most probably, the CHU station radio signals registered during the initial stage of the geomagnetic storm were scattered on the polar ovals' ionospheric inhomogeneities and propagated further along the return (long arc of the great circle) paths. Redistribution of the ionospheric plasma during the geomagnetic storm leads to the formation of HF radio propagation channels absent under quiet conditions. [ABSTRACT FROM AUTHOR]

Living organisms have evolved within the natural electromagnetic fields (EMFs) of the earth which comprise the global atmospheric electrical circuit, Schumann resonances (SRs) and the geomagnetic field. Research suggests that the circadian rhythm, which controls several physiological functions in the human body, can be influenced by light but also by the earth's EMFs. Cyclic solar disturbances, including sunspots and seasonal weakening of the geomagnetic field, can affect human health, possibly by disrupting the circadian rhythm and downstream physiological functions. Severe disruption of the circadian rhythm increases inflammation which can induce fatigue, fever and flu-like symptoms in a fraction of the population and worsen existing symptoms in old and diseased individuals, leading to periodic spikes of infectious and chronic diseases. Possible mechanisms underlying sensing of the earth's EMFs involve entrainment via electrons and electromagnetic waves, light-dependent radical pair formation in retina cryptochromes, and paramagnetic magnetite nanoparticles. Factors such as electromagnetic pollution from wireless devices, base antennas and low orbit internet satellites, shielding by non-conductive materials used in shoes and buildings, and local geomagnetic anomalies may also affect sensing of the earth's EMFs by the human body and contribute to circadian rhythm disruption and disease development.

Earth’s magnetic field is generated in the fluid outer core through the dynamo process. Over the last decade, data assimilation has been used to retrieve the core dynamics and predict the evolution of the geomagnetic field. The presence of model errors in the geomagnetic data assimilation is inevitable because current numerical geodynamo models are still far from realistic core dynamics. In this paper, we investigate the effect of model errors in geomagnetic data assimilation based on ensemble Kalman filter (EnKF). We construct two dynamo models with different control parameters but exhibiting similar force balance and magnetic morphology at the core surface. We then use one dynamo model to generate synthetic observations and the other as the forward model in EnKF. Our test experiments show that the EnKF approach with the pre-setting model errors can nevertheless recover large-scale core surface flow and make a rough short-term (5-year) prediction. However, the data assimilation in the presence of model errors cannot keep improving the core state even though new observations are available. Motivated by the planned Macau Science Satellite-1, which is expected to provide improved internal geomagnetic field model, we also perform a test experiment using synthetic observations up to spherical harmonic degree \begin{document}$\ell=18$\end{document}. Our results indicate that high-resolution observations are crucial in reconstructing small scale flow.

The European Space Agency (ESA)’s Swarm constellation of a trio of geomagnetic survey satellites in nearly circular polar orbits at altitude about \begin{document}$500$\end{document} km was launched on 22 November 2013 and has been mapping the Earth’s global magnetic field in unprecedented details, helping scientists better understand how the geomagnetic field is generated and maintained inside the Earth’s fluid core and how the Earth’s external magnetic environment is changing. This review discusses a new novel constellation of the geomagnetic survey satellites that consists of at least four satellites: two satellites are in lower-latitude and nearly circular orbits at altitude about \begin{document}$450$\end{document} km; two further satellites are marked by nearly polar but strongly eccentric orbits with perigee about \begin{document}$200$\end{document} km and apogee about \begin{document}$5000$\end{document} km. The new geomagnetic satellites are equipped with highly stable optical benches, high-precision fluxgate magnetometers and scalar magnetometers which are capable of mapping the Earth’s three-dimensional magnetic field in unprecedented accuracies and details. The new constellation will help elucidate different contributions to the measured geomagnetic field: the core dynamo field, the lithospheric magnetic field, the magnetic fields produced by currents in the ionosphere and the magnetosphere as well as by the currents coupling the ionosphere and magnetosphere, and the magnetic fields induced from the electrically conducting mantle, lithosphere and oceans. In comparison to the Swarm mission, it will provide higher-accuracy, higher-resolution and higher-dimension measurements of the geomagnetic field required for shedding new insights into the core dynamo processes and the Earth’s space magnetic systems along with a wide range of important applications.

We combined domestic ground-based and satellite magnetic measurements to create a regional three-dimensional surface Spline (3DSS) gradient model of the main geomagnetic field over the Chinese continent. To improve the precision of the model, we considered the data gap between the ground and satellite data. We compared and analyzed the results of the Taylor polynomial, surface Spline, and CHAOS-6 (the CHAMP, Ørsted and SAC-C model of Earth’s magnetic field) gradient models. Results showed that the gradients in the south−north and east−west directions of the four models were consistent. The 3DSS model was able to express not only gradients at different altitudes, but also average gradients inside the research area. The two Spline models were able to capture more information on gradient anomalies than were the fitted models. Strong local anomalies were observed in northern Xinjiang, Beijing, and the junction area between Jiangsu and Zhejiang, and the total intensity F decreased whereas the altitude increased. The gradient decreased by 21.69% in the south−north direction and increased by 11.78% in the east−west direction. In addition, the altitude gradient turned from negative to positive while the altitude increased. The Spline model and the two fitted models differed mainly in the field sources they expressed and the modeling theory.

Earth's magnetic field, which is generated in the liquid outer core through the dynamo action, undergoes changes on timescales of a few years to several million years, yet the underlying mechanisms responsible for the field variations remain to be elucidated. In this study, we apply a novel data analysis technique developed in fluid dynamics, namely the dynamic mode decomposition, to analyze the geomagnetic variations over the last two decades when continuous satellite observations are available. The dominant dynamic modes are extracted by solving an eigen-value problem, so one can identify modes with periods longer than the time span of data. Our analysis show that similar dynamic modes are extracted from the geomagnetic secular variation and secular acceleration, justifying the validity of applying the dynamic mode decomposition method to geomagnetic field. We reveal that the geomagnetic field variations are characterized by a global mode with period of 58 years, a localized mode with period of 16 years and an equatorially trapped mode with period of 8.5 years. These modes are possibly related to magnetohydrodynamic waves in the Earth's outer core.

The secular variation in the global geomagnetic field was analyzed in terms of the annual differences in monthly means by using the hourly mean data from 18 foreign (outside China) observatories of the World Data Center (WDC) for Geomagnetism from January 2010 to January 2020 as well as 9 observatories in the Geomagnetic Network of China from January 2015 to April 2021. In addition, according to the correlation of noisy components from the observatories, a covariance matrix was constructed based on residuals between observations and the CHAOS-7.4 model to remove external contamination. Through a comparison before and after denoising, we found that the overall average standard deviations were reduced by 29.97% in China and by 41.4% outside China. Results showed the correlation coefficient between external noise (mainly the magnetosphere ring current) and the Dst index was 0.82, and the correlation coefficient between external noise and the Ring Current (RC) index reached 0.94. A geomagnetic jerk was globally discovered around 2018.0 on the geomagnetic eastward component Y. The jerk timing in China was around 2020.0, and the earliest one was in 2018.75, whereas the timing outside China was around 2018.0, and the earliest one was in 2017.67. This 2-year lag may have been caused by the higher electrical conductivity of the deep mantle. After more data were added, this jerk event was found to occur in an orderly manner in the northern hemisphere as the longitude increased and the intensity gradually increased as well. The variations in location of the jerk center were analyzed according to the CHAOS-7.4 model. Results revealed six extreme points distributed nearby the equator. The strongest was near the equator, at 170°E, and the strength gradually decreased as it extended to the northern and southern hemispheres. Another extreme point with the opposite sign was located at the equator, at 20°W, in the south-central part of the Atlantic, and the strength gradually decreased as it extended into Europe. The covariance matrix method can be used to analyze data from the Macau Science Satellite-1 mission in the future, and this method is expected to play a positive role in modeling and separating the large-scale external field.

Magnetostratigraphy has become increasingly popular among geologists worldwide, as evidenced by recent scientific publications. This article reviews the role and place of magnetostratigraphy in general stratigraphic studies. The problem of developing a magnetostratigraphic scale of the Brunhes epoch based on paleosecular variation in the direction or intensity of the geomagnetic field was discussed. Nowadays, the above method has been actively pursued by researchers. Some hitherto little explored problems related to it were considered. Special attention was paid to the applicability range of the local magnetostratigraphic scale on the Earth’s surface. Three methods for estimating this parameter were proposed. Possible causes for the bias of paleomagnetic records in lava flows were analyzed: displacement of a recording medium during the recording process or later, magnetic anisotropy of two types, as well as the distortion of the geomagnetic field due to uneven surface magnetism, unevenly cooling lava magnetism, magnetism of surrounding rocks, or magnetohydrodynamic properties of flowing lava. The issues addressed here are important for improving the quality and reliability of paleomagnetic data.

Badai geomagnet terjadi akibat masuknya angin surya berkecepatan tinggi karena lontaran massa korona bersama dengan medan magnet. Badai geomagnet dipercaya membawa dampak besar di lintang tinggi dan semakin menurun sampai ke lintang rendah ekuator magnet. Penelitian ini untuk mengetahui bahwa tidak selamanya respon medan magnet di ekuator yang paling kecil. Penelitian ini menggunakaan data variasi medan magnet bumi dari Stasiun Geofisika Deli Serdang (TUN) dan 5 observatorium magnet bumi dari INTERMAGNET (CKI, PHU, IRT, GNG, CSY) dan badai geomagnetik pada tahun 2020. Pengolahan data variasi harian diawali dengan menghitung FFT dari seluruh sinyal yang terekam pada saat terjadi badai geomagnetik untuk memperoleh nilai SR (solar regular). Selanjutnya pada data variasi harian dari stasiun, nilai SR dihilangkan untuk mendapatkan nilai gangguan dari matahari. Data harian dibagi dalam interval tiga jam. Nilai simpangan maksimum di setiap interval kemudian dihitung pada komponen H dan Z. Hasil analisis menunjukkan bahwa TUN (lintang geomagnetik -3,74°) yang berlokasi di ekuator (lintang paling kecil), respon medan geomagnetik saat terjadi badai geomagnetik tidak menunjukan nilai yang paling kecil. Stasiun yang memberikan respon paling kecil adalah CKI (lintang geomagnetik -21,55°) dan IRT (lintang geogmagnetik 48,12°) kemudian stasiun yang memberikan respon paling tinggi adalah CSY (lintang geomagnetik -80,49°) yang berlokasi di dekat kutub selatan.