Hasil untuk "Geomagnetism"

Robert F. Butler

Ying‐Ming Zhang, Yao-Hua Liu, Y. Liu

Cyclodextrins (CDs), which are a class of cyclic oligosaccharides extracted from the enzymatic degradation of starch, are often utilized in molecular recognition and assembly constructs, primarily via host–guest interactions in water. In this review, recent progress in CD‐based supramolecular nanoassemblies that are sensitive to chemical, biological, and physical stimuli is updated and reviewed, and intriguing examples of the biological functions of these nanoassemblies are presented, including pH‐ and redox‐responsive drug and gene delivery, enzyme‐activated specific cargo release, photoswitchable morphological interconversion, microtubular aggregation, and cell–cell communication, as well as a geomagnetism‐controlled nanosystem for the suppression of tumor invasion and metastasis. Moreover, future perspectives and challenges in the fabrication of intelligent CD‐based biofunctional materials are also discussed at the end of this review, which is expected to promote the translational development of these nanomaterials in the biomedical field.

Takashi Minoshima, Yoshizumi Miyoshi, Go Murakami et al.

Abstract We analyze a unique solar energetic particle event observed simultaneously by the BepiColombo and STEREO-A spacecraft on March 30, 2022. The two spacecraft at heliocentric distances of 0.6 and 1.0 AU are expected to be aligned approximately along the same magnetic field line, providing a valuable opportunity to investigate particle transport processes in the inner heliosphere. Protons with energies above 1.0 MeV exhibit velocity dispersion during the rise phase, suggesting that the energetic particles are produced close to the Sun, possibly associated with a coronal mass ejection. In contrast, protons during the decay phase are characterized by long-lasting time profiles with longer time scales at 1.0 AU than at 0.6 AU, suggesting that the particles deviate from ballistic propagation. By assimilating these multi-spacecraft observation data into numerical simulations of the focused transport equation, for the first time, we estimate the mean free path parallel to the magnetic field as a time series. The inferred mean free path decreases over time and approaches around 0.5–1.0 AU at the STEREO-A location during the decay phase, suggesting an increasing influence of scattering on particle transport. This interpretation is qualitatively supported by independent STEREO-A observations that showed increasing magnetic field fluctuations, suggesting the connection between the particle transport and the local field fluctuations. However, only a fraction of these fluctuations is expected to contribute to particle scattering, which may be due to the multidimensional nature of magnetic field fluctuations. Graphical abstract

Mariana Bessa Fagundes, André Luis Albuquerque dos Reis, Anderson Costa dos Santos et al.

The present study integrates the magnetometric with petrographic data from the Morro de São João (MSJ) Alkaline Complex to investigate the magmatic evolution of the complex. The findings emphasize the critical role of magma mixing processes in shaping the textural and compositional diversity of MSJ rocks. The complex is a circular and conical body of approximately 10 km² located southeast of Rio de Janeiro composed of alkaline rocks strongly-silica undersaturation. The study used conventional petrographic analysis and aeromagnetic data processing, such as the Total Gradient Amplitude (TGA) and Reduction to the pole (RTP) maps to reveal the presence of multiple anomalous domains, supporting the hypothesis of non-cogenetic magmatic bodies that interacted during magma mixing events. To accomplish these objectives, this study employs a cross-correlation method to estimate the magnetization direction of the magnetic source. From a geodynamic perspective, the evolution of the MSJ’s evolution is supposed to be closely linked to geomagnetic polarity reversals, mantle plume activity, and extensional tectonic processes associated with the break-up of the Gondwana paleocontinent. These factors contributed to the generation of alkaline magmatism through the decompression of the subcontinental lithospheric mantle and the thermal influence of deep mantle plumes.

CAI Meifeng

Under the action of the Earth’s inner dynamics, the lithosphere shapes different types of the Earth’s surface, and the crustal stress state and its dynamic change law are captured by the comprehensive observation technology of drilling crustal activity. It is an important way for human beings to understand the internal dynamic process of the Earth and study the mechanism of inner dynamic geological hazards. The contribution of developed countries such as Japan, the USA, and the IODP International Cooperative Research Program to the development of integrated borehole crustal observation technology is summarized in this paper. The paper also systematically reviews the development history and present situation of borehole strain observation technology and borehole strain observation instrument in China. Especially since the 13th Five-Year, under the background of the national strategy of deep-sea exploration, the China Geological Survey Bureau (CGS), the China Earthquake Administration, and other systems have successively carried out research and development of the integrated geophysics observation system in wells, and have been put into use in integrated land and sea observation stations. The Institute of Geomechanics has successfully developed an integrated geophysics observation system for crustal activity using the key techniques of system integration. The system has a variety of strain, tilt, seismic, geomagnetic, geothermal, pore pressure, other sensors, and 16 components capable of observing crustal deformation, stress, strain, tilt, earthquake, and their induced geodynamic changes in the lithosphere, such as geotemperature, hydrology, geoelectricity, geomagnetism, etc. It has been put into use in Shandan (installed depth 253 m) and Pingwu (WFSD-4, 1600 m) observatories in Gansu and Sichuan provinces and has achieved initial results. It is a milestone for our comprehensive crustal activity observation technology to break through the 3000-meter-deep well in the future. It can provide vital information for geodynamics research, safe exploitation of deep mineral and geothermal resources, and prediction of internal dynamic geological hazards. At the same time, based on the national strategy of deep-sea exploration in the 14th Five-year, the future development direction of integrated observation system of deep-well crustal activity is pointed out.

Sheng‐Cheng Yeh, Chuan‐Jiang Lai, Fuan Tsai et al.

Abstract Location‐based services (LBSs) in such indoor places as museums, airport terminals, and train stations are becoming more and more popular among smartphone users. Hence, the research on indoor positioning technologies is increasing. Indoor positioning technologies using Wi‐Fi or Bluetooth wireless signals have some problems that cannot be overcome, for example, inconsistent data caused by human body shadowing effects. Positioning accuracy and stability still need to be improved to provide higher quality LBS applications. Smartphones have built‐in geomagnetic and acceleration sensors, and the Earth's magnetic field is not affected by human body shadowing effects, so it increases the appeal of using geomagnetism to enable indoor positioning with smartphones. This article proposed approaches in light of calibration‐free fingerprinting positioning techniques with terrestrial magnetism databases for indoor environments. For the differences in measurements yielded by various mobile phone (MP) models and brands, adjustments can be made using the ratio of the total intensity of the magnetic field and its horizontal component to correct the discrepancies. Finally, with the arrangement of four landmarks, the average error distance of the research results in the experimental environment is 3.59 m. The average accuracy of the k‐nearest neighbour (k‐NN) mobile phones is 71.3%.

Bayartogtokh Enkhzul, Erdenechimeg Batmagnai, Shoovdor Tserendug et al.

In this paper, we report a preliminary result of the Magnetotelluric investigation of the Mogod area. The Mogod region is one of the most prominent fields for geophysical study since the region includes young and active faults and geothermal activities. We conducted magnetotelluric measurements at 20 sites during geophysical field seasons in 2018-2021 as a pilot survey to understand data property and the electromagnetic noise level for the detailed electromagnetic studies. During the fieldwork, we used Lemi Magnetotelluric instruments and measured all three orthogonal components of the magnetic field and the horizontal components of the electric field. For the data processing, we used Matlab code by using the M-estimate regression method, and estimated the magnetotelluric transfer function with a lownoise level. The electrical resistivity model of the subsurface of survey layout shows us the existing resistivity anomalies at shallow-depth, and thickness of the upper crust approximately 11-17 km. Here, suggest that the thickness of the upper crust is 17 km and crust is 40 km with local magnetotelluric measurements. Additionally, the electric conductor appears in the southwest of Mogod region, we interpret that conductor play as a source of geological activity of Mogod region, and it might be the signature of a remanent fluid.

C. Ayala, E. Beamud, J. Huebert et al.

Abstract This article is composed of three independent commentaries about the state of Integrated, Coordinated, Open, Networked (ICON) principles (Goldman et al., 2021, https://doi.org/10.1002/essoar.10508554.1) in the Geomagnetism, Paleomagnetism, and Electromagnetism (GPE) section and discussion on the opportunities and challenges of adopting them. Each commentary focuses on a different topic: Global collaboration, reproducibility, data sharing and infrastructure; Inclusive equitable, and accessible science: Involvement, challenges, and support of early career, BIPOC, women, LGBTQIA+, and/or disabled researchers; Community engagement, citizen science, education, and stakeholder involvement. Data sharing practices and open repository use still varies strongly between GPE communities. Some have a long tradition of data sharing; others are only starting it. Globally, GPE leadership is strongly dominated by white males and diversity may increase through the creation of Science Equality Commissions. Improved global stakeholder involvement can increase research impacts and help fight inequalities. In all investigated topics we see promising beginnings but also recognize obstacles that include a lack of funding, a lack of understanding of diversity, and prioritizing short‐term gain over long‐term benefit. Nonetheless, we are hopeful that our community will embrace ICON science.

Sainath Aher, Keshav Deshmukh, Praveen Gawali et al.

The groundwater samples collected along the cross-section of Pravara river basin is quite distinct in terms of geo-hydrologic and anthropogenic situation. Innovative methods were used to investigate hydrogeochemical phases and groundwater quality for which 33 groundwater samples collected and analysed for pH (7.6–8.7), EC (311–1851 μS/cm), TDS (306–1990 mg/l), Na+ (11–296 mg/l), K+ (0.6–2.2 mg/l), Ca2+ (90–2001 mg/l), Mg2+ (1–17.9 mg/l), Cl− (71–1036 mg/l), SO42− (17–118 mg/l), NO3− (5.1–14 mg/l), CO32− (14.4–40.8 mg/l), HCO3− (117–698 mg/l) and F− (0.05–1.34 mg/l). The water quality was inferred with the help of water quality index (WQI) and Wilcox diagram. Fluid properties and irrigation water characteristics, as well as ion balance and Piper diagram were coupled to explore the type of water. Resourcesat-2 satellite image was processed to know the land use land cover (LULC) of area and its effect on groundwater. The results of pH, K+, Ca2+, Mg2+, SO42−, and NO3− were found within the prescribed limit. According to WQI, total 10 samples on RS and 09 samples on LS were found to have excellent quality water (57.58%) and 04 samples on RS and 05 samples on LS are good water (27.27%). The resulting Wilcox diagram also classifies the groundwater as excellent to good and good to permissible. The hydrochemical facies found Ca2+-Cl− type along RS and Mg2+-HCO3− type along LS. Based on hydrogeochemical characteristics and groundwater quality, the cross sectional aquifer is inferred to be predominantly influenced by natural as well as man induced causes, which have been validated by LULC results.

Monika Korte, Catherine G. Constable, Christopher J. Davies et al.

There has been longstanding controversy about whether the influence of lateral variations in core-mantle boundary heat flow can be detected in paleomagnetic records of geomagnetic field behavior. Their signature is commonly sought in globally distributed records of virtual geomagnetic pole (VGP) paths that have been claimed to exhibit specific longitudinal preferences during polarity transitions and excursions. These preferences have often been linked to thermal effects from large low seismic velocity areas (LLVPs) in the lowermost mantle, but the results have been contested because of potential sensitivity to sparse temporal and spatial sampling. Recently developed time varying global paleofield models spanning various time intervals in 1–100 ka, three of which include excursions, allow us to complement assessments of spatial distributions of transitional VGP paths with distributions of minimum field intensity. Robustness of the results is evaluated using similar products from four distinct numerical dynamo simulations with and without variable thermal boundary conditions and including stable geomagnetic polarity, excursions and reversals. We determine that VGP distributions are less useful than minimum field intensity in linking the influences of thermal CMB structure to geographical variations in actual paleofield observables, because VGP correlations depend strongly on good spatial sampling of a sufficient number of relatively rare events. These results provide a basis for evaluating comparable observations from four paleofield models. The distribution of VGP locations provide unreliable results given the restricted time span and available data locations. Rough correlations of global distributions of minimum intensity with areas outside the LLVPs give some indications of mantle control during excursions, although the results for the eastern hemisphere are complex, perhaps highlighting uncertainties about the hemispheric balance between thermal and compositional variations in the lowermost mantle. However, access to other geomagnetic properties (such as intensity and radial field at the CMB) provides a strong argument for using extended and improved global paleofield models to resolve the question of mantle influence on the geodynamo from the observational side.

Yuichi Otsuka, Luca Spogli, S. Tulasi Ram et al.

The 2nd Equatorial Plasma Bubble (EPB) workshop, funded by the Institute of Geology and Geophysics, Chinese Academy of Sciences, and the National Natural Science Foundation of China, took place in Beijing, China during September 13–15, 2019. The EPB workshop belongs to a conference series that began in 2016 in Nagoya, Japan at the Institute for Space-Earth Environmental Research, Nagoya University, resulting in a special issue of Progress in Earth and Planetary Science that focused on EPBs. The main goal of the series is to organize in-depth discussion by scientists working on ionospheric irregularities, and solve the scientific challenges in EPB and ionospheric scintillation forecasting. The 2nd EPB workshop gathered almost 60 scientists from seven countries. A total of 20 invited and contributing papers focusing on ionospheric irregularities and scintillations were presented. Here we briefly comment on 10 papers included in this special issue.

Shoya Matsuda, Yoshizumi Miyoshi, Satoko Nakamura et al.

Magnus D. Hammer, Grace A. Cox, William J. Brown et al.

Abstract We present geomagnetic main field and secular variation time series, at 300 equal-area distributed locations and at 490 km altitude, derived from magnetic field measurements collected by the three Swarm satellites. These Geomagnetic Virtual Observatory (GVO) series provide a convenient means to globally monitor and analyze long-term variations of the geomagnetic field from low-Earth orbit. The series are obtained by robust fits of local Cartesian potential field models to along-track and East–West sums and differences of Swarm satellite data collected within a radius of 700 km of the GVO locations during either 1-monthly or 4-monthly time windows. We describe two GVO data products: (1) ‘Observed Field’ GVO time series, where all observed sources contribute to the estimated values, without any data selection or correction, and (2) ‘Core Field’ GVO time series, where additional data selection is carried out, then de-noising schemes and epoch-by-epoch spherical harmonic analysis are applied to reduce contamination by magnetospheric and ionospheric signals. Secular variation series are provided as annual differences of the Core Field GVOs. We present examples of the resulting Swarm GVO series, assessing their quality through comparisons with ground observatories and geomagnetic field models. In benchmark comparisons with six high-quality mid-to-low latitude ground observatories we find the secular variation of the Core Field GVO field intensities, calculated using annual differences, agrees to an rms of 1.8 nT/yr and 1.2 nT/yr for the 1-monthly and 4-monthly versions, respectively. Regular sampling in space and time, and the availability of data error estimates, makes the GVO series well suited for users wishing to perform data assimilation studies of core dynamics, or to study long-period magnetospheric and ionospheric signals and their induced counterparts. The Swarm GVO time series will be regularly updated, approximately every four months, allowing ready access to the latest secular variation data from the Swarm satellites.

I.K. Pashkevich, M.I. Orlyuk, A.V. Marchenko et al.

This paper presents the results of a comprehensive analysis of geological and geophysical data, carried out to substantiate the existence and nature of transition class of magnetic anomalies produced by the Earth’s core and the lithosphere. This class of anomalies with a wavelength of 2000—4000 km belongs to the overlap region of the geomagnetic field spectra of the core and the lithosphere, and therefore their separation is arbitrary. The original technology of identifying the lithospheric component developed by the authors is based on one of the fundamental principles of geomagnetism — the change in time and space of the Earth’s core field and the stable position of the lithospheric anomalies. The lithospheric component containing anomalies with a wavelength of more than 2400 km was separated from the main geomagnetic field ВIGRF-12. The subject of our research is the submeridional Central European magnetic anomaly of this class, traced from the northern coast of Europe to the edge of the East Saharan mesocraton in Africa. To substantiate its mantle nature information was analyzed on tectonic position of the anomaly and distribution of local magnetic anomalies in the crust, relief of the Moho discontinuity, thickness of the lower (mafic) crust, average velocities VР of the crystalline crust. The inhomogeneity of the Earth’s crust cannot explain the anomaly under study, and therefore it is of mantle in nature. The distribution of the physical parameters of the crust and the tectonic position of the anomaly indicate the possible presence of a long-lived transregional lithospheric lineament such as a suture zone along its axis. Generalization of theoretical and experimental data suggests that under certain thermodynamic, reductive-oxidative, and tectonic conditions of the upper mantle, ferrimagnetic minerals (magnetite, hematite, native iron, and alloys of iron with nickel and cobalt) can exist, transform and form again within a wide range of Curie temperatures from 580 °C to 1100 °C. It limitsthe lower boundary of the magnetization stability at a depth of 600—640 km. The most favorable conditions for the origin of such sources are areas of subduction and relics of relatively cold slabs, suture zones and associated with them present-day fluids and plumes. In the area of the anomaly under study, fluids and the Iberian plume were identified from seismic tomographic data, which, in combination with the rise of the bottom of the upper mantle and the presence of inclined high-velocity layers in its low-velocity part, characterize the excited mantle. Thus, the Central European long-wave magnetic anomaly can be interpreted as the total effect of the relicts of primary ferrimagnets formed under the influence of fluidization of the mantle.

Annemarieke Béguin, Greig A. Paterson, Andrew J. Biggin et al.

Abstract Paleointensity.org is an online, open source, application to analyze paleointensity data produced by the most common paleointensity techniques. Our application currently supports four different methods: thermal Thellier (all variations), microwave Thellier, pseudo‐Thellier, and the multispecimen protocol. Data can be imported using a variety of input file formats such as ThellierTool files, the generic PmagPy file format, and a number of lab‐specific formats. The data for the individual paleointensity methods are visualized by the relevant graphs and parameters, which are updated dynamically while interpreting the data. Beyond manual interpretation, Paleointensity.org features an autointerpreter for specimen level Thellier‐type data. Interpretations and data can be exported to csv and MagIC files. Moreover, it is possible to export the local storage containing all data, saved interpretations, and settings. This file can be shared among researchers or attached to a paper as supporting information. Because of its many features and ease of use, Paleointensity.org is a major step forward in enhancing an open paleomagnetic community in which data can be shared, checked, and reused in line with the findable, accessible, interoperable, and reusable data principles.

Seungho Kuk, Junha Kim, Yongtae Park et al.

The high linear correlation between the smartphone magnetometer readings in close proximity can be exploited for physical human contact detection, which could be useful for such applications as infectious disease contact tracing or social behavior monitoring. Alternative approaches using other capabilities in smartphones have aspects that do not fit well with the human contact detection. Using Wi-Fi or cellular fingerprints have larger localization errors than close human contact distances. Bluetooth beacons could reveal the identity of the transmitter, threatening the privacy of the user. Also, using sensors such as GPS does not work for indoor contacts. However, the magnetometer correlation check works best in human contact distances that matter in infectious disease transmissions or social interactions. The omni-present geomagnetism makes it work both indoors and outdoors, and the measured magnetometer values do not easily reveal the identity and the location of the smartphone. One issue with the magnetometer-based contact detection, however, is the energy consumption. Since the contacts can take place anytime, the magnetometer sensing and recording should be running continuously. Therefore, how we address the energy requirement for the extended and continuous operation can decide the viability of the whole idea. However, then, we note that almost all existing magnetometer-based applications such as indoor location and navigation have used high sensing frequencies, ranging from 10 Hz to 200 Hz. At these frequencies, we measure that the time to complete battery drain in a typical smartphone is shortened by three to twelve hours. The heavy toll raises the question as to whether the magnetometer-based contact detection can avoid such high sensing rates while not losing the contact detection accuracy. In order to answer the question, we conduct a measurement-based study using independently produced magnetometer traces from three different countries. Specifically, we gradually remove high frequency components in the traces, while observing the correlation changes. As a result, we find that the human coexistence detection indeed tends to be no less, if not more, effective at the sampling frequency of 1 Hz or even less. This is because unlike the other applications that require centimeter-level precision, the human contacts detected anywhere within a couple of meters are valid for our purpose. With the typical smartphone battery capacity and at the 1 Hz sensing, the battery consumption is well below an hour, which is smaller by more than two hours compared with 10 Hz sampling and by almost eleven hours compared with 200 Hz sampling. With other tasks running simultaneously on smartphones, the energy saving aspect will only become more critical. Therefore, we conclude that sensing the ambient magnetic field at 1 Hz is sufficient for the human contact monitoring purpose. We expect that this finding will have a significant practicability implication in the smartphone magnetometer-based contact monitoring applications in general.

P. Mahavarkar, J. John, V. Dhapre et al.

A tri-axial square Helmholtz coil system for the study of palaeomagnetic studies, manufactured by GEOFYZIKA (former Czechoslovakia), was successfully commissioned at the Alibag Magnetic Observatory (IAGA code: ABG) in the year 1985. This system was used for a few years, after which the system encountered technical problems with the control unit. Rectification of the unit could not be undertaken, as the information document related to this system was not available, and as a result the system had been lying in an unused state for a long time, until 2015, when the system was recommissioned and upgraded to a test facility for calibrating the magnetometer sensors. We have upgraded the system with a constant current source and a data-logging unit. Both of these units have been designed and developed in the institute laboratory. Also, re-measurements of the existing system have been made thoroughly. The upgraded system is semi-automatic, enabling non-specialists to operate it after a brief period of instruction. This facility is now widely used at the parent institute and external institutions to calibrate magnetometers and it also serves as a national facility. Here the design of this system with the calibration results for the space-borne fluxgate magnetometers is presented.

R. Telschow, C. Gerhards, M. Rother

<p>The extraction of the magnetic signal induced by the oceanic M2 tide is typically based solely on the temporal periodicity of the signal. Here, we propose a system of tailored trial functions that additionally takes the spatial constraint into account that the sources of the signal are localized within the oceans. This construction requires knowledge of the underlying conductivity model but not of the inducing tidal current velocity. Approximations of existing tidal magnetic field models with these trial functions and comparisons with approximations based on other localized and nonlocalized trial functions are illustrated.</p>

Wooyeon Park, Jeongwoo Lee, Yu Yi et al.

Storm sudden commencements (SSCs) occur due to a rapid compression of the Earth's magnetic field. This is generally believed to be caused by interplanetary (IP) shocks, but with exceptions. In this paper we explore possible causes of SSCs other than IP shocks through a statistical study of geomagnetic storms using SYM-H data provided by the World Data Center for Geomagnetism – Kyoto and by applying a superposed epoch analysis to simultaneous solar wind parameters obtained with the Advanced Composition Explorer (ACE) satellite. We select a total of 274 geomagnetic storms with minimum SYM-H of less than –30nT during 1998-2008 and regard them as SSCs if SYM-H increases by more than 10 nT over 10 minutes. Under this criterion, we found 103 geomagnetic storms with both SSC and IP shocks and 28 storms with SSC not associated with IP shocks. Storms in the former group share the property that the strength of the interplanetary magnetic field (IMF), proton density and proton velocity increase together with SYM-H, implying the action of IP shocks. During the storms in the latter group, only the proton density rises with SYM-H. We find that the density increase is associated with either high speed streams (HSSs) or interplanetary coronal mass ejections (ICMEs), and suggest that HSSs and ICMEs may be alternative contributors to SSCs.

G. S. Lakhina, B. T. Tsurutani, A. C.-L. Chian et al.