Geomagnetic Diurnal Variation Research Articles

Detection and characterization of geomagnetic anomaly waveforms

Geomagnetic anomalies are abnormal changes in the geomagnetic field caused by changes in the stress of the underground rock. Research on geomagnetic anomaly signals can help explore earthquake prediction. This study proposes a window-weighted correlation degree (WWC) method to detect geomagnetic vertical component anomaly waveforms, addressing the limitations of traditional methods. The WWC method calculates the similarity between geomagnetic and reference data in daytime and nighttime windows, identifying abnormal signals based on change values. This method achieves a 0.976 accuracy in identifying geomagnetic anomaly waveforms, effectively detecting and recognizing complex waveform features in the geomagnetic field. Further, based on this method, a dataset of geomagnetic anomaly waveforms under various earthquake events was built, identifying seven typical anomalies. Five types of features were selected and constructed to measure the non-random deviation of diurnal geomagnetic variation from the baseline signal, improving the precision and recall of the random forest classification model. The machine learning method can classify and predict geomagnetic anomaly waveforms related to earthquake occurrence with superior precision and recall compared to traditional methods. This approach offers a productive means for identifying geomagnetic anomaly waveforms associated with earthquake occurrence and analyzing the potential correlations between anomalies and seismic events. It also provides a possibility for exploring the physical mechanism involved in geomagnetic anomalies' generation and evolution process. It provides effective data support for further analysis of seismic-magnetic relationships and helps to promote the deep integration of artificial intelligence and earthquake prediction research.

STUDY OF THE MULTIFRACTALITY OF GEOMAGNETIC VARIATIONS AT THE BELSK OBSERVATORY

The study of the dynamics of periodic variations with periods from 1 to 27 days using the wavelet transform and scaling analysis by the method of maxima of the modules of the wavelet transform coefficients is carried out using the results of instrumental observations of the geomagnetic field performed at the Belsk Central Geophysical Observatory in 2008 and 2018 (low solar activity) and in 2014 (high solar activity). A change in the intensity of periodic variations is established. Close to monofractal nature of diurnal geomagnetic variations is shown. The 27-day variation and its harmonics have a higher degree of multifractality during solar activity maximum compared to solar activity minimum.

Taylor Polynomial Spatial Reference Field Method for Field Geomagnetic Diurnal Variation Reduction

Taylor Polynomial Spatial Reference Field Method for Field Geomagnetic Diurnal Variation Reduction

A relatively dry mantle transition zone revealed by geomagnetic diurnal variations.

The distribution of water within the mantle transition zone (MTZ) has important implications for the material circulation and partial melting of the mantle. Although solubility of hydrogen is very high, leading to speculations that the MTZ plays a key role in the deep-Earth water cycle, the actual water content remains an open question. Electrical conductivity of mantle minerals is very sensitive to water content, so reliable estimates of this physical parameter in the MTZ would provide valuable constraints. Here, we use recently developed joint inversion of geomagnetic diurnal variation for realistic source structure and one-dimensional mantle conductivity profile. Synthetic tests show that the resulting profile is a reasonable proxy for the electrical conductivity distribution of continental mantle over depths where model resolution is best (200 to 600 kilometer), even in the presence of lateral heterogeneity. The inferred water concentration in the MTZ is 0.03 weight %, one to two orders of magnitude below the solubility of wadsleyite and ringwoodite.

Macroscopic nonlocal correlations by new data of the Baikal Experiment

The long-term Baikal experiment on study of macroscopic nonlocal correlations between random dissipative heliogeophysical processes and probe ones in the detectors have revealed prominent features of macroscopic entanglement predicted by action-at-a-distance electrodynamics. These correlations have both the retarded and advanced components with large time shifts. The correlations occur at extremely low frequencies and require long series of observations, so the Baikal experiment is continuing to study their unusual properties. In 2019-2021 new data were obtained on correlation of the signals of spaced detectors with each other and with to the natural processes: solar and hydrodynamic activity in Lake Baikal, as well as with the earthquake. The possibility of forecasting of solar and hydrodynamic activity on nonlocal correlations is demonstrated. Recently we paid attention to relatively short periods and discovered unexpected in-phase diurnal variation in the signals of both deep-sea detectors. This diurnal variation is not related to any hydrological processes. Moreover, this variation turned out in-phase with that one recorded by the remote lab detector (at the longitude difference 67°), that is it occurs in universal time, and cannot be associated with the meteorological or geomagnetic diurnal variations. The source of this signal in nonlocal correlation detectors is unknown yet.

Local time dependence of earthquakes occurrence and its possible connection with geomagnetic diurnal variations

ABSTRACT Occurrence of earthquakes is not only controlled by internal processes such as the tectonic processes, but also by external ones as Sun-Earth system processes. The aim of the current study is to examine the distribution of earthquakes occurrence at some active seismic regions in order to determine the dominant period of earthquakes occurrence with respect to local time and its possible connection with geomagnetic diurnal variations. Analyzing long-term datasets from 1986 to 2020 demonstrated that the occurrence of earthquakes at the studied regions is strongly depending on local time where earthquakes tend to occur more often during noon local time. This behavior is in somehow similar to the pattern of geomagnetic diurnal variations. Therefore, the study was extended to investigate the probable correlation between both of them. Diurnal variation of North-South geomagnetic component (X-component) was examined and compared with the local time distribution of earthquakes at each region. Data analysis revealed a significant correlation between the geomagnetic diurnal variations and earthquakes occurrence. Thus, the results support the idea of existence a dominating time interval of earthquakes occurrence and also a relationship between local time dependence of earthquakes and geomagnetic diurnal variations that may help in earthquakes prediction in the future.

Statistical Global Investigation of Pre-Earthquake Anomalous Geomagnetic Diurnal Variation Using Superposed Epoch Analysis

Recent studies reported that the diurnal variation of the geomagnetic field exhibited anomalous characteristics several months before earthquakes (EQs). However, the statistical significance of such anomalies detected using the diurnal variation range ratio (DVRR) method still requires verification as only a limited number of EQs occurring in certain seismoactive zones were included. In this study, the DVRR method was employed in conjunction with the superposed epoch analysis (SEA) to perform a large-scale study. A total of 157 EQs that occurred between 2000 and 2019 were investigated using vast geomagnetic field data collected from 92 ground-based magnetometer stations spread across multiple global regions. The case study conducted on the May 13, 2011, M6.1 Honshu (Japan) EQ showed that the diurnal variation of the vertical geomagnetic component disappeared around a week before the EQ. The case study also demonstrated the effectiveness of the DVRR method in minimizing solar disturbance influences, further proving that the observed anomalies were not caused by the Sun. The subsequent SEA revealed statistically significant increases in anomaly counts before the occurrence of EQs for all three geomagnetic components. The number of anomalies gradually increased approaching the day of EQs with temporal lags between the components. Furthermore, a control group analysis confirmed the findings by demonstrating that the increases were not coincidental and several explanations have been suggested, focusing primarily on the emergence and generation mechanisms of the anomalies. Results from this study showed that the anomalies were significant and were potentially precursors to the succeeding EQs.

Statistical significance of geomagnetic diurnal variation anomalies prior to worldwide earthquakes

Statistical significance of geomagnetic diurnal variation anomalies prior to worldwide earthquakes

Influence of Geomagnetic Disturbances at Different Times of Day on Locomotor Activity in Zebrafish (Danio Rerio).

The influence of magnetic fields and natural geomagnetic storms on biological circadian rhythms are actively studied. This study reveals an impact of local natural perturbations in the geomagnetic field that occurred at different times of the day on circadian patterns of locomotor activity of zebrafish. A decrease in zebrafish swimming speed was observed during the geomagnetic disturbances before or after the fluctuations of diurnal geomagnetic variation. However, if the geomagnetic perturbations coincided with the fluctuations of diurnal geomagnetic variation, the decrease in zebrafish swimming speed was insignificant. This result suggests that the biological effects of geomagnetic disturbances may depend on synchronization with the diurnal geomagnetic variation. It implies that the previously published correlations between geomagnetic activity and medical or biological parameters could result from a disruption in circadian biorhythms.

The Influence of Changes in Magnetic Variations and Light-Dark Cycle on Life-History Traits of Daphnia magna.

Day-night cycle is the main zeitgeber (time giver) for biological circadian rhythms. Recently, it was suggested that natural diurnal geomagnetic variation may also be utilized by organisms for the synchronization of these rhythms. In this study, life-history traits in Daphnia magna were evaluated after short-term and multigenerational exposure to 16 h day/8 h night cycle, 32 h day/16 h night cycle, diurnal geomagnetic variation of 24 h, simulated magnetic variation of 48 h, and combinations of these conditions. With short-term exposure, the lighting mode substantially influenced the brood to brood period and the lifespan in daphnids. The brood to brood period, brood size, and body length of crustaceans similarly depended on the lighting mode during the multigenerational exposure. At the same time, an interaction of lighting mode and magnetic variations affected to a lesser extent brood to brood period, brood size, and newborn's body length. The influence of simulated diurnal variation on life-history traits in daphnids appeared distinctly as effects of synchronization between periods of lighting mode and magnetic variations during the multigenerational exposure. Newborn's body length significantly depended on the lighting regime when the periods of both studied zeitgebers were unsynchronized, or on the interaction of light regime with magnetic variations when the periods were synchronized. These results confirm the hypothesis that diurnal geomagnetic variation is an additional zeitgeber for biological circadian rhythms. Possible mechanisms for these observed effects are discussed. Bioelectromagnetics. © 2020 Bioelectromagnetics Society.

Effect of a Shift in Diurnal Geomagnetic Variation on the Activity and Sensitivity of Digestive Glycosidases in Roach Underyearlings to Heavy Metals

The effect of temporal shifts in diurnal geomagnetic variation with 6- and 12-h intervals relative to the day–night cycle on the activity of digestive glycosidases (maltase and amylolytic activity) and their sensitivity to the in vitro influence of heavy metal ions (Cu2+, Zn2+, Pb2+, Cd2+) at a concentration of 25 mg/L has been studied in roach Rutilus rutilus (L.) underyearlings. Amylolytic activity (the total activity of starch-hydrolyzing enzymes: α-amylase, glucoamylase, and maltase) is determined by the modified Nelson method, maltase activity by the glucoseoxidase method with a Fotoglukoza clinical biochemistry kit. It is found that exposing embryos to both 6- and 12-h shifts in diurnal geomagnetic variation reduces the activity of maltase and its sensitivity to the effect of zinc and cadmium ions. Amylolytic activity increases only in roach underyearlings exposed to a 6-h shift in diurnal geomagnetic variation as embryos. The sensitivity of starch-hydrolyzing enzymes to the influence of copper (6- and 12-h shifts) and cadmium (12-h shift) increases. The decrease in the enzyme activity and its increased sensitivity to the inhibitory effect of heavy metals may reduce the efficiency of carbohydrate hydrolysis in roach underyearlings. The increase in the amylolytic activity can be considered as adaptation of the digestive system of the fish to a 6-h shift in diurnal geomagnetic variation relative to the day–night cycle during embryogenesis.

Spectra of the geomagnetic field diurnal variations

Spectral analysis of the geomagnetic field time series with the discreteness of 60 s (Intermagnet data) and a duration of, for example, 1 year (31×10 6 s) yields an average-annual amplitude spectrum over periods from approximately 500 s to 5×10 6 s. The spectrum consists of the continuous part (continuum spectrum) and narrow lines at the diurnal period T 0 =86400 s and its harmonics with periods T = T 0 / n , where n =2—7. The subject of this work is the diurnal line of the spectrum and its harmonics. The average-annual spectra of the geomagnetic field diurnal variations of 32 Intermagnet observatories in North America were calculated. Also the average-seasonal spectra of five observatories, which represent high, medium and low geomagnetic latitudes of both northern and southern hemispheres were obtained. At the near-pole high geomagnetic latitudes, only the daily harmonic T 0 is observed, at the geomagnetic equator 7 harmonics are observed, in the aurora zone and middle latitudes — an intermediate number of harmonics: from two to seven. The amplitude is maximal at high latitudes (50—80 nТ), less at the geomagnetic equator (≈40 nТ), and quite minor at middle latitudes (10—15 nТ). These results are in good agreement with the known data on diurnal variations. The used representation of the harmonics of diurnal period by spectral lines makes it easy and clearly to track the features of diurnal variations and their changes both according to the data of individual observatories and synchronous data of many observatories. An interesting new scientific result is the detected widening of the diurnal harmonic spectral line from September to February and the absence of the widening from March to August for all three considered years 2009—2011 at all five observatories. This is not a seasonal variation, since it is equally observed at observatories in both the northern and southern hemispheres, in which the seasons are in antiphase. We can assume that this phenomenon is associated with a certain orientation of the Earth in outer space relative to some factor that changes the daily spectral line to a wider one. The absolute motion of the Earth, formed by a hierarchy of cosmological rotations, is supposed as such a factor. A brief review of the literature on the determination of the parameters of absolute motion is given.

A simulated geomagnetic storm unsynchronizes with diurnal geomagnetic variation affecting calpain activity in roach and great pond snail.

It has been suggested that geomagnetic storms could be perceived by organisms via disruption of naturally occurring diurnal geomagnetic variation. This variation, in turn, is viewed by way of a zeitgeber for biological circadian rhythms. The biological effects of a geomagnetic storm, therefore, could depend on the local time of day when its main phase occurs. We have assessed calpain activity in tissues of roach (Rutilus rutilus) and great pond snail (Limnaea stagnalis) after exposure to a simulated geomagnetic storm, reproduced at different times of day, in order to evaluate this hypothesis. Significant decrease in calpain activity was observed in organisms exposed to the simulated geomagnetic storm whose main phase, and initial period of a recovery phase, did not coincide with the expected peak of diurnal geomagnetic variation. The results obtained are considered an experimental confirmation of the aforementioned hypothesis. Improvement of a correlative approach for the assessment of biological effects of geomagnetic activity can be achieved by considering information on the synchronization of geomagnetic storm's main phase with diurnal geomagnetic variation.

Background noise estimation of the geomagnetic signal

Abstract. A fast Fourier transform was applied to fit the geomagnetic diurnal variation. Fitting results showed that when the polynomial degree was greater than 160, the residual error was close to 0 nT. White noise is the main component of the residual error when the polynomial degree was greater than 160, so this method was adopted to calculate the background noise of the geomagnetic field. Spectrum analysis further demonstrated that the noise estimation result is reliable.

A reassessment of the anomalous geomagnetic diurnal variation two months prior to the 2011 Tohoku earthquake, Japan (Mw 9.0)

This study reassesses the claim of an anomalous geomagnetic diurnal variation two months prior to and northwest of the eventual epicenter of the 2011 Tohoku earthquake, Japan (Mw 9.0). Instead of discussing the ratios of geomagnetic diurnal variation ranges at observation and reference stations, which previous studies have analyzed, the ranges themselves are examined in the present work. For the reassessment, the technique to identify the range of typical variations is improved, leading to more appropriate values of the geomagnetic diurnal variation range than those obtained by previous studies. The variations that were deemed anomalous by previous authors can be explained by coupling of the ranges of three components of the geomagnetic diurnal variation; this coupling effect was not discussed in previous studies. The cause of the high ratio was a combination of low-amplitude quiet-day diurnal solar variations in the geomagnetic field in winter, day-to-day variations, and a weak magnetic disturbance during the period. It is therefore not strictly correct that the observed variations were anomalous and, as such, they cannot be unambiguously related to seismo-magnetic phenomena due to crustal activity prior to the megathrust earthquake. In addition, due to issues with the statistical treatment of samples in previous studies, a more appropriate statistical discussion of the matter is presented.

A Possible Influence of Seismic Activity on Diurnal Geomagnetic Variations

Recent research has introduced some evidences referring to a possible connection between the variation in geomagnetic field measurements and seismic activities. Thus, the present study focuses on a certain seismic activity that occurred at the northern part of Honshu Island, Japan to find out its impact on the diurnal geomagnetic variations recorded at this region. The study of variability of daily geomagnetic variations amplitude at the northern part of Honshu Island; which is characterized by high seismic activities has introduced motivating results. Data analysis and processing indicate the presence of an unusual change in the diurnal variations amplitude in association with earthquake activity occurred on 24 March 2008 at the studied area. A remarkable anomalous behavior in the diurnal variations amplitude of the East-West horizontal geomagnetic component (D-component) was detected in the vicinity of the epicenter at the Tohno station compared with those recorded at the Kakioka geomagnetic observatory and other remote reference stations. This anomalous behavior is observed only during the day of the studied seismic event, which suggests a possible connection between the earthquake occurrence and the change of diurnal variations range. Moreover, since there were no significant external geomagnetic changes during the occurrence of earthquake as revealed from the Dst and Kp indices, the observed anomalous variability in the diurnal geomagnetic variations range of D-component can be considered as anomalous phenomenon linked with the studied seismic activity. Such anomalous phenomenon can be used for constructing earthquake warning systems.

The effect of a temporal shift in diurnal geomagnetic variation on roach Rutilus rutilus L. embryos: A comparison with effects of simulated geomagnetic storms

A study was made of the effects that 6- and 12-h shifts in diurnal geomagnetic variation relative to the night–day light cycles exert on roach Ritulus ritulus L. embryos. Either temporal shift in diurnal geomagnetic variation stimulated blastomere proliferation and early prelarval hatching in exposed embryos compared to controls. Underyearlings developing from exposed embryos displayed higher locomotor activity in a plusshaped maze, a lower number of rays in the anal fin, a redistribution of vertebrae through sections of the vertebral column, and a higher number of seismosensory system openings in the mandibular and preopercular bones. The effects were similar to those described previously for roaches exposed to a simulated geomagnetic storm during embryonic development. The results support the hypothesis that animals perceive geomagnetic storms as a dramatic disturbance that occurs in the habitual diurnal geomagnetic variation at an unusual time relative to the night–day light cycle, which acts as a primary zeitgeber of circadian biological rhythms.

Biological effects related to geomagnetic activity and possible mechanisms.

This review presents contemporary data on the biological effects of geomagnetic activity. Correlations between geomagnetic indices and biological parameters and experimental studies that used simulated geomagnetic storms to detect possible responses of organisms to these events in nature are discussed. Possible mechanisms by which geomagnetic activity influences organisms are also considered. Special attention is paid to the idea that geomagnetic activity is perceived by organisms as a disruption of diurnal geomagnetic variation. This variation, in turn, is viewed by way of a secondary zeitgeber for biological circadian rhythms. Additionally, we discuss the utility of cryptochrome as a biological detector of geomagnetic storms. The possible involvement of melatonin and protein coding by the CG8198 gene in the biological effects of geomagnetic activity are discussed. Perspectives for studying mechanisms by which geomagnetic storms affect organisms are suggested. Bioelectromagnetics. 38:497-510, 2017. © 2017 Wiley Periodicals, Inc.

2011年東北地方太平洋沖地震（Mw9.0）に関連する地磁気日変化異常の時空間的特徴

Recent studies have reported unusual behaviors of geomagnetic diurnal variation (GDV) in the vertical component prior to the 2011 off the Pacific coast of Tohoku earthquake (Mw 9.0). To make a better understanding of this phenomenon, time-spatial analysis of GDV has been applied in this study. Geomagnetic data of long term observations at 17 stations in Japan have been analyzed using the same method in Han et al. 2015. Ratios of diurnal variation range between the target station and the reference station KAK have been computed. After removing seasonal variations revealed by wavelet transform analysis, the 15-day mean values of the ratios in the vertical component shows a clear anomaly exceeding the statistical threshold about 2 months before the mega event in both ESA and MIZ stations in the Tohoku Region. Similar results could not be found in other regions of Japan. Spatial distributions of the ratios show a good agreement between the location of the anomalies and the epicenter of Mw 9.0 earthquake. These time-spatial results are consistent with independent results obtained from other observations such as radon density, seismicity, and GPS displacements, which suggest the geomagnetic data might be useful in earthquake monitoring and disaster mitigation.

Can the comprehensive model phase 4 (CM4) predict the geomagnetic diurnal field for days away from quiet time?

Abstract. The most recent comprehensive model (CM4) of the geomagnetic field (Sabaka et al., 2004) has been used in conjunction with geomagnetic ground observatory station data to analyse and study the geomagnetic diurnal variation field for days away from quiet time and the CM4 prediction for these times. Even though much has been learnt about many components of the geomagnetic field, the diurnal variation field behaviour for days away from quiet time (moderately disturbed time) has not been intensively studied. Consequently, we analyse these, and the predictive ability of the CM4 for ground variations, and whether the CM4 prediction of the diurnal variation (whether at quiet time or away from quiet time) is valid outside the period of reference that from which the data were used in modelling. In carrying out the study, we compared the observatory station data and the CM4 prediction directly. Using the CM4 code, well-characterised internal and magnetospheric components were subtracted from the data, plots and global maps of the residual field generated and then compared with the CM4 to see how well the model performed in predicting the data at moderately disturbed time (Kp ≤ 5). The results show that the CM4 is valid and produces useful predictions outside the period covering the timespan of the model and during moderately disturbed time, despite the lack of active data in the original model dataset. The model predictability of the data increases as we move to higher spherical harmonic degree truncation, as the model–data misfit is reduced, but with increased roughness as a result of small-scale features incorporated. The observed results show that this relationship between the increase in spherical harmonic degree truncation and reduction in misfit can be restricted by data quality or quantity and global coverage or spread.