Hasil untuk "Geomagnetism"

Cheng Cui, Zhengxiang Xu, Zefeng Liu et al.

To address coverage gaps in high-latitude space weather monitoring caused by constraints in energy, bandwidth, and labeled samples, this study presents a systematic solution deployed in Hailar, China. We constructed a Cloud–Edge–Terminal system featuring wind–solar hybrid energy and RK3588-based edge computing, achieving six months of stable ionospheric–geomagnetic observation under −40 °C. Furthermore, we propose a Dual-Adversarial Recurrent Autoencoder (DA-RAE) for anomaly detection. Utilizing a single-source domain strategy, the model learns physical manifolds from quiet-day data, enabling zero-shot anomaly perception in the unsupervised target domain. Field tests in March 2025 demonstrated superior generalized anomaly detection capabilities, successfully identifying both transient space weather events and environmental equipment faults (baseline drifts). This work validates the value of edge intelligence for autonomous operations in extreme environments, providing a reproducible paradigm for global ground-based networks.

Heliásio Augusto Simões, Moab Praxedes Gomes, Patrícia Reis Alencar Oliveira et al.

The exhumation and exposure of mantle rocks is a common process that takes place during the tectono-magmatic evolution of a newly created lithosphere along slow- and ultraslow-spreading oceanic ridges, such as the Equatorial Mid-Atlantic Ridge. A geophysical survey conducted in 2012 and 2013 between the Bogdanov (7º 10’ N) to the St. Paul (0º 50’ N) fracture zones revealed lower crust and upper mantle rocks exposures through asymmetric accretion along low-angle normal faults, i.e., the Oceanic Core Complexes, laterally associated with other morpho-tectonic features. The dataset consists of multi-beam bathymetry (100 m/pixel) and ship gravity (1,750 m/pixel) covering an area of 40,000 km2. Seismicity and satellite free-air anomaly data are included. Three oceanic transform faults and nine non-transform offsets were identified and mapped along the ridge axis. Oceanic Core Complexes are characterized by corrugated and non-corrugated massifs, back-tilted ridges indicating detachment breakaways, and various detachment morphologies. These features typically exhibit bathymetric patterns that are roughly parallel to the accretion direction, positive Bouguer anomalies, and low seismic activity. Twelve Oceanic Core Complexes consistently occur at non-transforming discontinuities and asymmetric accretion segments. These mantle outcroppings indicate a low melt supply during the recent tectono-magmatic evolution of this region of the Mid-Atlantic Ridge.

Rajesh Kumar Barad, S. Sripathi, Ram Singh et al.

Abstract This study explores the ionospheric response over the Indian sector to the G4‐class geomagnetic storm of 23–24 April 2023. Utilizing multi‐instrument observations and SAMI2 modeling, ionospheric behavior was examined during the storm's main phase (17:41 UT, 23 April–04:03 UT, April 24) and the recovery phase (04:03 UT–22:44 UT, 24 April). During the main phase, ionosonde data from Tirunelveli showed rapid F‐layer height (h’F) variations driven by westward and eastward prompt penetration electric fields (PPEFs). The westward PPEF, induced by undershielding, led to an initial decrease in h’F followed by an increase, suppressing pre‐existing Equatorial Plasma Bubbles (EPBs) within two hours of the storm's onset. Despite a late‐night rise in h’F due to overshielding, no new EPB formed. The recovery phase exhibited a positive storm effect at low latitudes and a negative effect at higher latitudes, linked to disturbance dynamo electric fields (DDEFs) and thermospheric composition changes (Σ[O]/[N2] ratio). Large‐scale traveling ionospheric disturbances were clearly evident in GNSS TEC and ionosonde data, with a ∼2‐hr period, ∼2,450 km wavelength, and ∼340 m/s equatorward speed, likely driven by auroral/Joule heating‐induced atmospheric gravity waves. On 24 April, the westward DDEF suppressed the daytime equatorial ionization anomaly (EIA) and inhibited post‐sunset EPBs, while eastward DDEF increased h’F in the post‐midnight without EPB formation. We speculate that this absence might be due to a lack of seeding mechanisms. SAMI2 simulations incorporating E × B drift data reproduced several storm‐time features in the main and recovery phases.

Batmagnai Erdenechimeg, Alexey Kuvshinov

Mongolia is a unique natural laboratory for studying intracontinental surface deformation and intraplate volcanism due to its location within the high plateaus of the Central Asian Orogenic Belt, far away from active plate margins. The region is also characterized by zones of economically significant mineral deposits and vast geothermal resources, which are intrinsically linked to its lithospheric architecture and crust-mantle interactions. Key earth’s properties, such as temperature, fluid content, and partial melt, influence the subsurface electrical conductivity - a target parameter of the magnetotelluric method. Between 2016 and 2024, two large-scale international magnetotelluric projects were conducted, resulting in more than 784 magnetotelluric measurements across a vast area of about 1000×1250 km2. Additionally, from 2019 to 2023, a focused international magnetotelluric study was carried out at the geothermal field near Tsenkher in the Khangai Mountains, with 256 magnetotelluric measurements over a smaller area of about 35×40 km2. These projects contributed significantly to understanding the region’s lithospheric processes and geothermal systems. Crucially, the knowledge transfer from these collaborative projects has enabled Mongolian researchers to initiate and perform their own magnetotelluric surveys to explore geologically significant areas across the region. This review details performed magnetotelluric surveys (as of the end of 2024), highlights the key results, and discusses potential directions for future research.

Tomoe Taki, Satoshi Kurita, Airi Shinjo et al.

Abstract We analyzed electrostatic electron cyclotron harmonic waves observed by the interferometry observation mode of the Arase satellite. It is found that the magnitude of the phase difference varies with the satellite spin. The spin dependence of this phase difference was investigated by examining the trend of the spin dependence for the 84 events of interferometry observation of ECH waves. We found that they are divided into two categories. One is that the phase difference tends to show sinusoidal variations as a function of the angle $$\gamma _B$$ γ B between the ambient magnetic field projected on the spin plane and the electric field sensor. The other is that the phase difference is close to zero and does not depend on $$\gamma _B$$ γ B . A numerical model of interferometry observation of single plane wave is constructed to explain the observed phase differences. We performed the numerical calculations when the background magnetic field was oriented in the direction often observed in the Arase satellite. The result of the calculations shows the wave vector direction relates to the spin angle with the maximum phase difference. Using this relation, we show that it may be possible to estimate the wave vector direction of ECH waves from one-dimensional interferometry data. This is expected to enable more accurate estimates of phase velocity. Graphical Abstract

Helen Mavromichalaki, Maria Livada, Argyris Stassinakis et al.

A novel tool utilizing machine learning techniques was designed to forecast ap index values for the next three consecutive days (24 values). The tool employs time series data from the 3 h ap index of solar cycles 23 and 24 to train the Long Short-Term Memory (LSTM) model, predicting ap index values for the next 72 h at three-hour intervals. During periods of quiet geomagnetic activity, the LSTM model’s performance is sufficient to yield favorable outcomes. Nevertheless, during geomagnetically disturbed conditions, such as geomagnetic storms of different levels, the model needs to be adapted in order to provide accurate ap index results. In particular, when coronal mass ejections occur, the ap Prediction tool is modulated by inserting predominant features of coronal mass ejections such as the date of the event, the estimated time of arrival and the linear speed. In the present work, this tool is described thoroughly; moreover, results for G2 and G3 geomagnetic storms are presented.

R. Rubia, S. V. Singh, G. S. Lakhina et al.

Electrostatic solitary waves (ESWs) in the Venusian ionosphere that are impinged by the solar wind are investigated using a homogeneous, collisionless, and magnetized multicomponent plasma consisting of Venusian H ^+ and O ^+ ions, Maxwellian Venusian electrons and streaming solar wind protons, and suprathermal electrons following κ − distribution. The model supports the propagation of positive potential slow O ^+ and H ^+ ion-acoustic solitons. The evolution and properties of the solitons occurring in two sectors, viz., dawn-dusk and noon-midnight sector of the Venus ionosphere at an altitude of (200–2000) km, are studied. The theoretical model predicts positive potential solitons with amplitude ∼(0.067–56) mV, width ∼(1.7–53.21) m, and velocity ∼(1.48–8.33) km s ^−1 . The bipolar soliton electric field has amplitude ∼(0.03–27.67) mV m ^−1 with time duration ∼(0.34–22) ms. These bipolar electric field pulses when Fourier transformed to the frequency domain occur as a broadband electrostatic noise, with frequency varying in the range of ∼9.78 Hz–8.77 kHz. Our results can explain the observed electrostatic waves in the frequency range of 100 Hz–5.4 kHz in the Venus ionosphere by the Pioneer Venus Orbiter mission. The model can also be relevant in explaining the recent observation of ESWs in the Venus magnetosheath by the Solar Orbiter during its first gravity assist maneuver of Venus.

Jeffrey J. Love, E. Joshua Rigler, Michael D. Hartinger et al.

Abstract An analysis is made of geophysical records of the 24 March 1940, magnetic storm and related reports of interference on long‐line communication and power systems across the contiguous United States and, to a lesser extent, Canada. Most long‐line system interference occurred during local daytime, after the second of two storm sudden commencements and during the early part of the storm's main phase. The high degree of system interference experienced during this storm is inferred to have been due to unusually large‐amplitude and unusually rapid geomagnetic field variation, possibly driven by interacting interplanetary coronal‐mass ejections. Geomagnetic field variation, in turn, induced geoelectric fields in the electrically conducting solid Earth, establishing large potential differences (voltages) between grounding points at communication depots and transformer substations connected by long transmission lines. It is shown that March 1940 storm‐time communication‐ and power‐system interference was primarily experienced over regions of high electromagnetic surface impedance, mainly in the upper Midwest and eastern United States. Potential differences measured on several grounded long lines during the storm exceeded 1‐min resolution voltages that would have been induced by the March 1989 storm. In some places, voltages exceeded American electric‐power‐industry benchmarks. It is concluded that the March 1940 magnetic storm was unusually effective at inducing geoelectric fields. Although modern communication systems are now much less dependent on long electrically conducting transmission lines, modern electric‐power‐transmission systems are more dependent on such lines, and they, thus, might experience interference with the future occurrence of a storm as effective as that of March 1940.

Ram Kumar Vankadara, Punyawi Jamjareegulgarn, Gopi Krishna Seemala et al.

The equatorial plasma bubbles (EPBs) are depleted plasma density regions in the ionosphere occurring during the post-sunset hours, associated with the signal fading and scintillation signatures in the trans-ionospheric radio signals. Severe scintillations may critically affect the performance of dynamic systems relying on global navigation satellite system (GNSS)-based services. Furthermore, the occurrence of scintillations in the equatorial and low latitudes can be triggered or inhibited during space weather events. In the present study, the possible presence of the EPBs during the geomagnetic storm periods under the 25th solar cycle is investigated using the GNSS-derived total electron content (TEC) depletion characteristics at a low-latitude equatorial ionization anomaly location, i.e., KL University, Guntur (Geographic 16°26′N, 80°37′E and dip 22°32′) in India. The detrended TEC with a specific window size is used to capture the characteristic depletion signatures, indicating the possible presence of the EPBs. Moreover, the TEC depletions, amplitude (S4) and phase scintillation (σ_φ) indices from multi-constellation GNSS signals are probed to verify the vulnerability of the signals towards the scintillation effects over the region. Observations confirm that all GNSS constellations witness TEC depletions between 15:00 UT and 18:00 UT, which is in good agreement with the recorded scintillation indices. We report characteristic depletion depths (22 to 45 TECU) and depletion times (28 to 48 min) across different constellations confirming the triggering of EPBs during the geomagnetic storm event on 23 April 2023. Unlikely, but the other storm events evidently inhibited TEC depletion, confirming suppressed EPBs. The results suggest that TEC depletions from the traditional geodetic GNSS stations could be used to substantiate the EPB characteristics for developing regional as well as global scintillation mitigation strategies.

Christine Gabrielse, Justin H. Lee, Seth Claudepierre et al.

Abstract We use NASA's Van Allen Probes data to build a 3‐dimensional Radiation Belt Daily Average Electron flux model (RB‐Daily‐E) covering 25 differential energies (33–7,700 keV), 17 pitch angles, and a variable number of L shells from 2 to 7. RB‐Daily‐E can be used to deduce the fluences observed by any satellite that flew within Van Allen Probes' 7‐year mission lifetime. We supplement Van Allen Probes fluxes with THEMIS average fluxes to cover higher L shells when applying the model to a secondary satellite. RB‐Daily‐E agrees with both the Arase high‐energy electron experiment (XEP) flux data and the GPS Combined X‐ray Dosimeter (CXD) electron flux approximately within a factor of two or better, and comparisons with AE9 are as expected. The RB‐Daily‐E Model has applications for when actual fluxes on day‐timescales are required for post‐anomaly investigations, including long‐term radiation environment effects such as solar cell and solar array degradation. We therefore applied the model to two GPS satellites to determine electron fluence inputs to the Equivalent Flux (EQFLUX) solar cell degradation model. The modeled voltage degradation well‐matched the voltage degradation trends identified in the GPS telemetry data, suggesting that the radiation environment is the primary cause of the voltage degradation. The current degradation was largely underestimated, suggesting that current degradation is influenced by other sources.

Hai Yang, Li Li, Tao Luo et al.

In the oil industry, directional drilling technology plays a significant role in oil-gas exploration. The key to success of directional drilling technology is locate the borehole accurately using measurement while drilling instruments. Measurement While Drilling(MWD) technology has the problems of data loss and gross error in complex down hole environment. Aiming at the problems that gross error and data missed consequences the accuracy of positioning calculation seriously, this paper presents a method of fault-tolerant integrated borehole trajectory location based on geomagnetism/IMU of MWD system. Firstly, the geomagnetic survey system is established to locate the borehole position based on tri-axis fluxgate and tri-axis accelerometer. The Inertial Measurement Unit(IMU) calculates the borehole trajectory at the same time. Then, the fault-tolerant judgment mechanism is introduced to discriminate and evaluate data loss and gross error of measurement parameters. Furthermore, Kalman Filter algorithm is implied to construct fault-tolerant integrated borehole trajectory positioning system. Finally, the simulation experiment is performed on the drilling experimental platform. The experimental result shows that the fault-tolerant integrated borehole trajectory positioning system can detect data loss and gross error effectively. In addition, the location precision of the fault-tolerant integrated positioning system can be maintained within 1 meter when the time of data missed and gross error state lasts for 6min respectively. From the simulation experiments, comparing with the position calculation of pure geomagnetism, and the method of integrated MEMS and geomagnetism, the precision of the fault-tolerant integrated location calculation is improved by 68.7% and 62.8% respectively.

Andrei Vladimirovich Vorobev, Gulnara Ravilevna Vorobeva, Nafisa Islamovna Yusupova

Задача мониторинга параметров геомагнитного поля и его вариаций преимущественно решается сетью магнитных обсерваторий и вариационных станций, однако значимым препятствием при обработке и анализе получаемых таким образом данных наряду с их пространственной анизотропией являются пропуски (или полное отсутствие) достоверных значений и частичное несоответствие установленному формату. Неоднородность и аномальность данных исключает (существенно усложняет) возможность их автоматической интеграции и применения к ним инструментария для частотного анализа. Известные решения по интеграции разнородных геомагнитных данных базируются преимущественно на модели консолидации и лишь частично решают данную проблему. Получаемые в результате наборы данных, как правило, не соответствуют требованиям IAGA (International Association of Geomagnetism and Aeronomy — Международной ассоциации геомагнетизма и аэрономии), рекомендуемым к представлению результатов геомагнитных наблюдений. При этом пропуски во временных рядах устраняются известными средствами обработки геомагнитных данных путем исключения отсутствующих или аномальных значений из конечной выборки, что, очевидно, может привести как к потере актуальной информации о ходе изменения параметров геомагнитного поля и его вариаций, нарушению шага дискретизации, так и к неоднородности временного ряда. Предлагается подход к созданию единого пространства геомагнитных данных, основанный на комбинировании моделей консолидации и федерализации, включающий предварительную обработку исходных временных рядов с опционально доступной процедурой их восстановления и верификации, ориентированный на применение технологий облачных вычислений и иерархического формата с целью повышения вычислительной скорости обработки больших объемов данных и, как следствие, обеспечивающий получение пользователями более качественных и однородных данных.

Anatoly Soloviev, Vincent Lesur, Dmitry Kudin

Abstract We propose a new approach to the calculation of regular baselines at magnetic observatories. The proposed approach is based on the simultaneous analysis of the irregular absolute observations and the continuous time-series deltaF, widely used for estimating the data quality. The systematic deltaF analysis allows to take into account all available information about the operation of observatory instruments (i.e., continuous records of the field variations and its modulus) in the intervals between the times of absolute observations, as compared to the traditional baseline calculation where only spot values are considered. To establish a connection with the observed spot baseline values, we introduce a function for approximate evaluation of the intermediate baseline values. An important feature of the algorithm is its quantitative estimation of the resulting data precision and thus determination of the problematic fragments in raw data. We analyze the robustness of the algorithm operation using synthetic data sets. We also compare baselines and definitive data derived by the proposed algorithm with those derived by the traditional approach using Saint Petersburg observatory data, recorded in 2015 and accepted by INTERMAGNET. It is shown that the proposed method allows to essentially improve the resulting data quality when baseline data are not good enough. The obtained results prove that the baseline variability in time might be quite rapid.

P. Stauning

The International Association of Geomagnetism and Aeronomy (IAGA) has recently endorsed a new Polar Cap (PC) index version to supersede the previous seven different versions of the PCN (North) index and the five different PCS (South) index versions. However, the new PC index has some adverse features which should be known and taken into account by users of the index. It uses in its derivation procedure an "effective" quiet day level (QDC) composed of a "basic" QDC and an added solar wind sector term related to the azimuthal component (<i>B_y</i>) of the interplanetary magnetic field (IMF). The added IMF <i>B_y</i>-related terms may introduce unjustified contributions to the PC index of more than 2 index units (mV m⁻¹). Furthermore, cases of reverse convection during strong northward IMF <i>B_z</i> (NBZ) conditions included in the database for calculation of index coefficients can cause unjustified index enhancements of 0.5–1 mV m⁻¹ during calm conditions, reduction of index values by more than 20 % during disturbed conditions, and inconsistencies between index coefficients and index values for the northern and southern polar caps. The aim here is to specify these adverse features and quantify their effects, and to suggest alternative steps for future modifications of the index procedure.

H Hayashi, Y Koyama, T Hori et al.

An overview of the Inter-university Upper atmosphere Global Observation NETwork (IUGONET) project is presented with a brief description of the products to be developed. This is a Japanese inter-university research program to build the metadata database for ground-based observations of the upper atmosphere. The project also develops the software to analyze the observational data provided by various universities/institutes. These products will be of great help to researchers in efficiently finding, obtaining, and utilizing various data dispersed across the universities/institutes. This is expected to contribute significantly to the promotion of interdisciplinary research, leading to more a comprehensive understanding of the upper atmosphere.

Cvetkov Vesna, Lesić Vesna, Vasković Nada

Fruška Gora Mountain is a large scale antiform located at the southeast part of the Pannonian Basin between the Danube and Sava Rivers. It is built of Paleozoic and Mesozoic rocks with Neogene sediments on all sides and at the flanks. The Paleozoic and Mesozoic rocks are largely metamorphosed (age of the metamorphism is early Cretaceous) and they are intruded by Eocene/Oligocene latites and rhyodacites and Badenian basaltic trachyandesite. On Fruška Gora two major structural units are observed, the northern and southern structural units which are divided by the Srem dislocation striking NNW-SSE. The Tertiary magmatic rocks located on both sides of this dislocation were the subject of paleomagnetic analysis. Tectonically meaningful paleomagnetic directions are obtained from latites and rhyodacites, while basaltic trachyandesite has a secondary remanent magnetization. The obtained overall-mean paleomagnetic direction, after applying the correction for the general tilt of the Lower Miocene sediments, suggests a clockwise rotation (D = 210°, I = -45°, k = 21, α95 = 14°) of 30° with respect to the present North of blocks on both sides of the Srem dislocation. The fact that close to the end of Miocene-Early Pliocene Fruška Gora rotated in a counterclockwise direction for 40° with respect to the present North means that all of Fruška Gora rotated in a clockwise direction for 70° with the respect to the present North in a short time after the intrusion of Eocene/Oligocene magmatic rocks and before Middle Miocene. [Projekat Ministarstva nauke Republike Srbije, br. 176016]

Wang-Ting Chang

Chen Li-hua

M. Kiss, I. Ekk, G. Tóth et al.

Chen Li-hua