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The history of the research on the SC (sudden commencement) of magnetic storms before World War II is studied in this paper. Since geomagnetic research activities before World War II are still not yet fully known, this paper aims to reveal some historical facts related to SC investigation at that time. The first conclusion of this paper is the possible first discoverer of the simultaneity of SC at distant locations. We show that a Portuguese scientist had already pointed it out 16 years earlier than believed. The second conclusion is the role and activities of Aikitu Tanakadate as the reporter of the SC investigation committee of STME (Section of Terrestrial Magnetism and Electricity) and IATME (International Association of Terrestrial Magnetism and Electricity) in the IGGU (International Geodetic and Geophysical Union) or IUGG (International Union of Geodesy and Geophysics). Very little was known about his activities as the reporter of this committee. Our investigation at the Tanakadate Aikitu Memorial Science Museum disclosed how he acted and what he thought of SC, based on his frequent letters to and from other scientists. The third conclusion concerns SC research carried out by Japanese scientists during the period of the Second International Polar Year (1932–1933). Not only Tanakadate but also many other Japanese scientists participated in SC research during this international project. This formed a traditional basis of SC investigation in Japan, prompting a number of Japanese scientists to study SC after World War II. [ABSTRACT FROM AUTHOR]

In order to study the imprints of solar-ENSO-geomagnetic activity on the Indian Subcontinent, we have applied the Singular Spectral Analysis (SSA) and wavelet analysis to the tree ring temperature variability record from the western Himalayas. The data used in the present study are the Solar Sunspot Number (SSN), Geomagnetic Indices (aa Index), Southern Oscillation Index (SOI) and tree ring temperature record from western Himalayas (WH), for the period of 1876-2000. The SSA and wavelet spectra reveal the presence of 5 years short term ENSO variations to 11 year solar cycle indicating the influence of both the solar-geomagnetic and ENSO imprints in the tree ring data. The presence of 33-year cycle periodicity suggests the Sun-temperature variability probably involving the induced changes in the basic state of the atmosphere. Our wavelet analysis for the SSA reconstructed time series agrees with our previous results and also enhance the amplitude of the signals by removing the noise and showing a strong influence of solar-geomagnetic and ENSO patterns throughout the record. The solar flares are considered to be responsible for cause in the circulation patterns in the atmosphere. The net effect of solar-geomagnetic processes on temperature record thus appears to be the result of counteracting influences on shorter (about 5-6 years) and longer (about 11-12 years) time scales. The present analysis thus suggests that the influence of solar processes on Indian temperature variability operates in part indirectly through ENSO, but on more than one time scale. The analyses hence provides credible evidence for teleconnections of tropical pacific climatic variability with Indian climate ranging from interannual-decadal time scales and also demonstrate the possible role of exogenic triggering in reorganizing the global earth-ocean-atmospheric systems. [ABSTRACT FROM AUTHOR]

Joint interpretation of magnetotelluric and geomagnetic depth sounding results in the period range of 10-105 s in the Western European Alps offer new insights into the conductivity structure of the Earth's crust and mantle. This first large scale electromanetic study in the Alps covers a cross-section from Germany to northern Italy and shows the importance of the alpine mountain chain as an interrupter of continuous conductors. Poor data quality due to the highly crystalline underground is overcome by Remote Reference and Robust Processing techniques and the combination of both electromagnetic methods. 3-D forward modeling reveals on the one hand interrupted dipping crustal conductors with maximum conductances of 4960 S and on the other hand a lithosphere thickening up to 208 km beneath the central Western Alps. Graphite networks arising from Palaeozoic sedimentary deposits are considered to be accountable for the occurrence of high conductivity and the distribution pattern of crustal conductors. The influence of huge sedimentary Molasse basins on the electromagnetic data is suggested to be minor compared with the influence of crustal conductors. Dipping direction (S-SE) and maximum angle (10.1°) of the northern crustal conductor reveal the main thrusting conditions beneath the Helvetic Alps whereas the existence of a crustal conductor in the Briançonnais supports theses about its belonging to the Iberian Peninsula. In conclusion the proposed model arisen from combined 3-D modeling of noise corrected electromagnetic data is able to explain the geophysical influence of various structural features in and around the Western European Alps and serves as a background for further upcoming studies. [ABSTRACT FROM AUTHOR]

The closure of the Mongo-Okhotsk ocean has a strong influence on the tectonic evolution of Northeast China. However, the dynamic mechanism in the Mongol-Okhotsk suture area is controversial. This paper intends to obtain the deep structure of beneath Northeast China based on geomagnetic depth sounding, and constrain the subduction of Mongol-Okhotsk Ocean from the perspective of electrical properties. This paper collects and processes the data of geomagnetic stations in China and adjacent areas, and obtains stable C -response data. The staggered grid finite difference method is used for forward modeling, and the finite memory quasi Newton method based on L 1-norm is used for inversion. The three-dimensional inversion of geomagnetic data is carried out in spherical coordinates. The intensive model testing stations can obtain high-resolution underground electrical structures. The measured data show that there are obvious high conductivity anomalies in the mantle transition zone in Northeast China, especially in the west of the Great Xing'an Range, showing an area of high conductivity anomalies. Combined with the regional tectonic background of the region, we speculate that the high conductivity anomaly body is related to the southward subduction of the Mongol-Okhotsk Ocean. The Mongol-Okhotsk Ocean subducted under the Eurasian plate at a small angle in the southward direction. With the closing of the Okhotsk Ocean and the extension environment after the termination of subduction, the subducted oceanic crust plate has been faulted and depressed and partially stopped in the mantle transition zone. [ABSTRACT FROM AUTHOR]

The paper discusses the accuracy of the scalar Coupled Dark State Magnetometer on board the Jupiter Icy Moon Explorer (JUICE) mission of the European Space Agency. The scalar magnetometer, referred to as MAGSCA, is part of the J-MAG instrument. MAGSCA is an optical, omni-directional scalar magnetometer based on coherent population trapping, a quantum interference effect, within the hyperfine manifold of the 87Rb D1 line. The measurement principle is only based on natural constants and therefore, it is in principle drift free and no calibration is required. However, the technical realisation can influence the measurement accuracy. The most dominating effects are heading characteristics, which are deviations of the magnetic field strength measurements from the ambient magnetic field strength. The verification of the accuracy and precision of the instrument is required to ensure its compliance with the performance requirement of the mission: 0.2 nT (1- σ). The verification is carried out with four dedicated sensor orientations in a Merritt coil system, which is located in the geomagnetic Conrad observatory. The coil system is used to compensate the Earth's magnetic field and to apply appropriate test fields to the sensor. This paper presents a novel method to separate the heading characteristics of the instrument from residual (offset) fields within the coil system by fitting a mathematical model to the measured data. It allows verifying that the MAGSCA sensor unit does not have a measurable remanent magnetisation as well as that the desired accuracy of 0.2 nT (1- σ) is achieved by the MAGSCA flight hardware for the JUICE Mission. [ABSTRACT FROM AUTHOR]

The measurement series of the three geomagnetic observatories Potsdam, Seddin and Niemegk spans 130 years, starting in 1890. It is one of the longest, almost uninterrupted series of recordings of the Earth's magnetic field. Data users frequently emphasise the high quality of the data and their significance for geomagnetic base research. Very well known outstanding geomagnetism scientists, such as Max Eschenhagen, Adolf Schmidt, Julius Bartels, Gerhard Fanselau and Horst Wiese, directed the observatories during their existence. This paper describes the history of the Seddin Observatory, which was in operation from 1907 until 1932. [ABSTRACT FROM AUTHOR]

This paper deals with the most intense magnetic storm of the 20th century, which took place on 13–15 May 1921. Part of this storm was observed in the magnetic declination and vertical intensity at Stará Ďala, currently known as Hurbanovo. However, the sensitivity of the magnetometer was not determined there in the years when the storm occurred. Here, we estimated the sensitivity scale values on the basis of data from before and after the studied event. The resulting digitized Stará Ďala's data for 13–15 May 1921 are the main contribution of this work. The data were also put into the context of the records from other observatories. The overall picture of the geomagnetic field variations compiled from the observations by worldwide observatories, including Stará Ďala, suggests that the auroral oval got close to Stará Ďala and other European mid-latitude observatories in the morning hours on 15 May 1921. [ABSTRACT FROM AUTHOR]

By documenting noise levels in 6.5 yr of nighttime measurements by the spaceborne lidar CALIOP above the South Atlantic Anomaly (SAA), we show they contain information about the evolution of upwelling high-energy radiation levels in the area. We find 5 the amount of noisy profiles is influenced by the 11 yr cycle of solar activity, fluctuates by ±5% between 2006 and 2013, and is anticorrelated with solar activity with a 1 yr lag. The size of the SAA grows as solar activity decreases, and an overall westward shift of the SAA region is detectable. We predict SAA noise levels will increase anew after 2014, and will affect future spaceborne lidar missions most near 2020. In other areas, supposedly unaffected by incoming sunlight, nighttime noise levels are much weaker but follow the same 11 yr cycle, superimposed with a one-year cycle that affects both hemispheres similarly and could be attributed to geomagnetic activity. [ABSTRACT FROM AUTHOR]

The measurement series of the three geomagnetic observatories Potsdam, Seddin and Niemegk spans more than 130 years, starting in 1890. It is one of the longest, almost uninterrupted series of recordings of the Earth's magnetic field. Data users frequently emphasise the high quality of the data and their significance for geomagnetic base research. Very well known outstanding geomagnetism scientists, such as Max Eschenhagen, Adolf Schmidt, Julius Bartels, Gerhard Fanselau and Horst Wiese, directed the observatories during their existence. This paper describes the history of the Potsdam Observatory, which was in operation from 1890 until 1928. [ABSTRACT FROM AUTHOR]

The article presents a study that uses two spectral techniques in terms of Fourier and wavelet analysis to detect geometric jerks time series. It suggests that the analysis allows researchers to depict the most important space-time features of the geomagnetic jerks on global scale. It reveals that the spherical harmonic analysis of the secular acceleration power spectrum brings new insights in understanding the rapid changes of the geomagnetic field and their origin.

The Sheshan Geomagnetic Observatory (International Association of Geomagnetism and Aeronomy (IAGA) code SSH), China was built in Xujiahui, Shanghai in 1874 and moved to Sheshan, Shanghai at the end of 1932. So far, the SSH has a history of nearly 150 years. It is one of the earliest geomagnetic observatories in China and one of the geomagnetic observatories with the longest history in the world. In this paper, we present the rescue and quality control (QC) of the historical data at the SSH from 1933 to 2019. The rescued data are the absolute hourly mean values (AHMVs) of declination (D), horizontal (H), and vertical (Z) components. Some of these data are paper-based records and some are stored in a floppy disk in BAS, DBF, MDB, and other file storage formats. After digitization and format transformation, we imported the data into the Toad database to achieve the unified data management. We performed statistics of completeness, visual analysis, outliers detects, and data correction on the stored data. We then conducted the consistency test of daily variation and secular variation (SV) by comparing the corrected data with the data of the reference observatory, and the computational data of the COV-OBS model, respectively. The consistency test reveals good agreement. However, the individual data should be used with caution because these data are suspicious values, but there is not any explanation or change registered in the available metadata and logbooks. Finally, we present examples of the datasets in discriminating geomagnetic jerks and study of storms. The digitized and quality-controlled AHMVs data are available at: 10.5281/zenodo.7005471 (Zhang et al., 2022). [ABSTRACT FROM AUTHOR]

From the perspective of the social history of science and transnational history, this paper reviewed the development of the Institute of Geophysics, Chinese Academy of Sciences (IGCAS), rather than focusing on its scientific achievements. Before the 1950s, the discipline of geophysics in China, except for the branch of meteorology, had a very weak foundation, and few researchers were engaged in it. The systematic development of geophysics began with the establishment of IGCAS. In this paper, the early development of IGCAS was researched thoroughly. At first, we briefly reviewed the establishment process for IGCAS. After being promoted by the desire of scientists to develop big geophysics, the Chinese Academy of Sciences (CAS) integrated scattered academic forces, which included geomagnetism and geophysical exploration, to establish the IGCAS. The IGCAS was based on the Institute of Meteorology of Academia Sinica in the Republic of China era. After that, we summarized work done by IGCAS in the development of geophysics from the 1950s to 1966, the year in which the Cultural Revolution began. We focused on policy support, adjustment of organizational structure, and scientific capacity building, when China was facing an isolated international diplomatic environment, continuous domestic political movements, and an austere social economy. Then, to bolster the development of geophysics in China, the slogan of "Missions Drive Disciplines", which was instilled and implemented by the Chinese scientific community, was introduced briefly. The scientific development of the IGCAS and typical examples in several branches of geophysics, which included atmospheric science, seismology, space physics, and other fields, were systematically summarized and benchmarked to the international academic level. We then summarized the basic research on geophysics carried out by the institute in economic construction and national defense. Finally, the experience and lessons in the development of this institute and its effect on geophysics in China were explored. [ABSTRACT FROM AUTHOR]

Swarm is the European Space Agency (ESA)'s first Earth observation constellation mission, which was launched in 2013 to study the geomagnetic field and its temporal evolution. Two Langmuir probes aboard each of the three Swarm satellites provide in situ measurements of plasma parameters, which contribute to the study of the ionospheric plasma dynamics. To maintain a high data quality for scientific and technical applications, the Swarm products are continuously monitored and validated via science-oriented diagnostics. This paper presents an overview of the data quality of the Swarm Langmuir probes' measurements. The data quality is assessed by analysing short and long data segments, where the latter are selected to be sufficiently long enough to consider the impact of the solar activity. Langmuir probe data have been validated through comparison with numerical models, other satellite missions, and ground observations. Based on the outcomes from quality control and validation activities conducted by ESA, as well as scientific analysis and feedback provided by the user community, the Swarm products are regularly upgraded. In this paper, we discuss the data quality improvements introduced with the latest baseline, and how the data quality is influenced by the solar cycle. In particular, plasma measurements are more accurate in day-side regions during high solar activity, while electron temperature measurements are more reliable during night side at middle and low latitudes during low solar activity. The main anomalies affecting the Langmuir probe measurements are described, as well as possible improvements in the derived plasma parameters to be implemented in future baselines. [ABSTRACT FROM AUTHOR]

On timescales longer than the solar cycle, long-term changes in CO 2 concentration and geomagnetic field have the potential to affect thermospheric dynamics. In this paper, we investigate the thermospheric dynamical response to these two factors during the Holocene, using two sets of ∼12000 -year control runs by the coupled thermosphere–ionosphere model, GCITEM-IGGCAS. The main results indicate that increased/decreased CO 2 will enhance/weaken the thermospheric circulation throughout the Holocene, but this effect is non-linear. The cooling effect of CO 2 in the thermosphere further provides plausible conditions for atmospheric tidal propagation and increases the thermospheric tidal amplitude. Geomagnetic variations induce hemispheric asymmetrical responses in the thermospheric circulation. Large changes in the circulation occur at high latitudes in the hemisphere with distant magnetic pole drift, inferring a crucial role of geomagnetic non-dipole variations in circulation changes. A positive correlation between the diurnal migrating tide (DW1) and geomagnetic dipole moment is revealed for the first time. The amplitude of DW1 in temperature will increase by ∼1 –3 K for each 1×1022 A m 2 increase in dipole moment. [ABSTRACT FROM AUTHOR]

In the concluding paper of this tetralogy, we here use the different geomagnetic activity indices to reconstruct the near-Earth interplanetary magnetic field (IMF) and solar wind flow speed, as well as the open solar flux (OSF) from 1845 to the present day. The differences in how the various indices vary with near-Earth interplanetary parameters, which are here exploited to separate the effects of the IMF and solar wind speed, are shown to be statistically significant at the 93% level or above. Reconstructions are made using four combinations of different indices, compiled using different data and different algorithms, and the results are almost identical for all parameters. The correction to the aa index required is discussed by comparison with the Ap index from a more extensive network of mid-latitude stations. Data from the Helsinki magnetometer station is used to extend the aa index back to 1845 and the results confirmed by comparison with the nearby St Petersburg observatory. The optimum variations, using all available long-term geomagnetic indices, of the near-Earth IMF and solar wind speed, and of the open solar flux, are presented; all with ±2σ uncertainties computed using the Monte Carlo technique outlined in the earlier papers. The open solar flux variation derived is shown to be very similar indeed to that obtained using the method of Lockwood et al. (1999). [ABSTRACT FROM AUTHOR]

The closure of the Mongo-Okhotsk ocean has a strong influence on the tectonic evolution of Northeast China. However, the dynamic mechanism in the Mongol-Okhotsk suture area is controversial. This paper intends to obtain the deep structure of beneath Northeast China based on geomagnetic depth sounding, and constrain the subduction of Mongol-Okhotsk Ocean from the perspective of electrical properties. This paper collects and processes the data of geomagnetic stations in China and adjacent areas, and obtains stable C-response data. The staggered grid finite difference method is used for forward modeling, and the finite memory quasi Newton method based on L1-norm is used for inversion. The three-dimensional inversion of geomagnetic data is carried out in spherical coordinates. The intensive model testing stations can obtain high-resolution underground electrical structures. The measured data show that there are obvious high conductivity anomalies in the mantle transition zone in Northeast China, especially in the west of the Great Xing'an Range, showing an area of high conductivity anomalies. Combined with the regional tectonic background of the region, we speculate that the high conductivity anomaly body is related to the southward subduction of the Mongol-Okhotsk Ocean. The Mongol-Okhotsk Ocean subducted under the Eurasian plate at a small angle in the southward direction. With the closing of the Okhotsk Ocean and the extension environment after the termination of subduction, the subducted oceanic crust plate has been faulted and depressed and partially stopped in the mantle transition zone. [ABSTRACT FROM AUTHOR]

Aeromagnetic exploration is an important method of geophysical exploration. We study the compensation method of the towed bird system and establish the towed bird interference model. Due to the geomagnetic gradient changing greatly, the geomagnetic gradient is considered in the towed bird interference model. In this paper, we model the geomagnetic field gradient and analyze the influence of the towed bird system on the aeromagnetic compensation results. Finally, we apply the ridge regression method to solve the problem. We verify the feasibility of this compensation method through actual flight tests and further improve the data quality of the towed bird interference. [ABSTRACT FROM AUTHOR]

Shortly after the introduction of the physical unit for the magnetic field in 1832 and the invention of the bifilar apparatus in 1837, both being extraordinary scientific achievements that took place in Göttingen, the Clementinum observatory in Prague became one of the first places where systematic observations of the horizontal intensity of the geomagnetic field began. Karl Kreil was decisively responsible for this. In this paper, we focus on the very beginnings of geomagnetic observations in Prague, dating from the middle of 1839. We describe the archival materials with data that exist from that time, how the main instrument for observing magnetic storms – the bifilar magnetometer – worked and how it was calibrated, and the first magnetic survey in Bohemia. This study indicates the importance of historical geomagnetic observation materials to modern science, such as space weather research. [ABSTRACT FROM AUTHOR]

The combined Fourier-wavelet (CFW) transform is a useful technique to characterize planetary-scale waves, such as tides and traveling planetary waves in the Earth's atmosphere. A CFW spectrum, presented in a time versus period diagram, can be used to identify wave activity that is localized in time, similar to a wavelet spectrum. A CFW spectrum can be obtained for each of eastward- and westward-propagating wave components with different zonal wavenumbers. This paper introduces an easy-to-implement method to derive CFW spectra in two steps. In the first step, the Fourier transform is performed in space (longitude), and time series of the space Fourier coefficients are derived. In the second step, the wavelet transform is performed on these time series, and wavelet coefficients are derived. It is shown that the CFW transform can be easily derived from these wavelet coefficients. The results suggest that existing Fourier and wavelet software can be utilized to derive CFW spectra. Matlab and Python scripts are created and made available at https://igit.iap-kborn.de/yy01/cfw that compute CFW spectra using the wavelet software provided by Torrence and Compo (1998). Some application examples are presented using longitude-time data from atmospheric and geomagnetic-field models. [ABSTRACT FROM AUTHOR]

High-precision indoor positioning in complex environments has always been a hot research topic within the positioning and robotic communities. As one of the indoor positioning technologies, geomagnetic positioning is receiving widespread attention due to its global coverage. Additionally, geomagnetic positioning does not require special infrastructure configuration, its hardware cost is low, and its positioning errors do not accumulate over time. However, geomagnetic positioning is prone to mismatching, which causes serious problems at the positioning points. To tackle this challenge, this paper proposes an indoor localization method based on spectral clustering and weighted back-propagation neural network. The main research contribution is that in the offline phase, the spatial specificity of geomagnetism is used to define the similarity between fingerprints. In addition, a clustering-based reference point algorithm is proposed to divide the sub-fingerprint database, and a positioning prediction model based on back-propagation neural network is trained. Subsequently, in the online stage, the weights of different positioning prediction models are calculated according to the defined fingerprint similarity, weighted average prediction coordinates are obtained, and thereby the positioning accuracy is improved. Experimental results show that, in comparison with other neural network-based positioning methods, the positioning error of our proposed algorithm is reduced by approximately 26.6% and the positioning time is reduced by 24.7%. Experimental results show that the average positioning error of the algorithm is 1.81m. [ABSTRACT FROM AUTHOR]

Kakioka Magnetic Observatory (KMO) was founded in 1913 by the Central Meteorological Observatory (CMO, later the Japan Meteorological Agency) as a successor to Tokyo Magnetic Observatory. Kakioka was a village 70 km north of Tokyo and was selected to escape from tram noise in Tokyo. At first, it was an unstaffed observatory only for geomagnetic field observation. Then, the Great Kanto Earthquake in 1923 changed the fate of KMO because the earthquake severely damaged the CMO in Tokyo, and recording papers of KMO were lost. KMO was staffed in 1924 and was redesigned as an institute for geophysics rather than geomagnetism. KMO operated a variety of observations, such as the atmospheric electric field, the geoelectric field, the seismicity, the air temperature, the wind velocity, the sunspot and solar prominence as well as the geomagnetic field, by the 1940s. In addition, research activity flourished with the leadership of the first director, Shuichi Imamichi. After World War II was over in 1945, KMO formed a network of observatories in Japan by founding several branch observatories originally for geoelectric field observation. Two branch observatories at Memambetsu and Kanoya survived, with geomagnetic field observation added in the International Geophysical Year project (1957–1958). Efforts in development of instruments for geomagnetic absolute measurement and systems of high-sampling recordings in the 1950s to 1970s resulted in the development of the Kakioka Automatic Standard Magnetometer (KASMMER) system in 1972. KASMMER measured the geomagnetic field every 3 s at the highest standard in the world in digital form, giving 1 min digital values of the geomagnetic field available. This system has been updated, and the high-sampling technology was applied to geoelectric field observation and atmospheric electric field observation. Later, adding geomagnetic field observation at Chichijima in 1971, KMO established a unique electric and magnetic observation network at Kakioka, Memambetsu, Kanoya and Chichijima and provided precise and high-speed sampling data (1 min, 1 and 0.1 s values) by 2001. On the other hand, KMO gradually terminated or automated their observations and reduced their staff in the last several decades following the government's reform policy. The two branch observatories at Memambetsu and Kanoya were unstaffed in 2011, and the atmospheric electric field at Memambetsu was terminated at that time. The geoelectric field observations at Kakioka, Memambetsu and Kanoya were terminated in 2021 as well as the atmospheric electric field at Kakioka. KMO focuses on geomagnetic observation for now and puts efforts into total force observation at volcanoes and the digitization of historic analog data. [ABSTRACT FROM AUTHOR]

In the last 60 years, the largest displacement of the magnetic equator (by about 1100 km northwards) occurred in the Brazilian longitudinal sector. The magnetic equator passed by Tatuoca magnetic observatory (TTB) in northern Brazil in 2012 and continues to move northward. Due to the horizontal geomagnetic field geometry at the magnetic equator, enhanced electric currents in the ionosphere are produced - the so called equatorial electrojet (EEJ). The magnetic effect of the EEJ is observed in the range of ± 3 degrees from the magnetic equator, where magnetic observatories record an amplified daily variation of the H component. In order to track the spatial and temporal variation of this phenomena, a new magnetometer station was installed in Macapá (MAA), which is about 350 km northwest from TTB. In this paper, we present the setup and data analysis of MAA station from 11/2019 until 09/2021. Because of its special configuration, we develop a method for temperature correction of the vector magnetometer data. [ABSTRACT FROM AUTHOR]

The comparative research of the influence of different types of auroral particle precipitation and polar cap patches (PCPs) on the global positioning system (GPS) signals disturbances in the polar ionosphere was done. For this purpose, we use the GPS scintillation receivers at Ny-Ålesund and Skibotn, operated by the University of Oslo. The presence of the auroral particle precipitation and polar cap patches was determined by using data from the EISCAT 42m radar on Svalbard. The optical aurora observations in 557.7 and 630.0 nm spectrum lines on Svalbard were used as well for the detection of ionospheric disturbances. The cusp identification was done with using SuperDARN (Hankasalmi) data. We consider events when the simultaneous EISCAT 42m and GPS data were available for the years 2010–2017, and in this paper we present, in detail, typical examples describing the overall picture, and we present the statistics for 120 events. We considered the dayside/cusp precipitation, substorm precipitation, daytime and nighttime PCPs, and precipitation associated with the interplanetary shock wave arrival. We demonstrate that substorm-associated precipitation (even without PCPs) can lead to a strong GPS phase (σϕ) scintillations up to ∼ 1.5–3 radians, which is much stronger than those usually produced by other types of considered ionosphere disturbances. The value of the substorm-phase scintillations in general correlate with the value of the geomagnetic field disturbance. But sometimes even a small geomagnetic substorm, when combined with the PCPs, produces quite strong phase scintillations. Cusp phase scintillations are lower than dayside PCPs scintillations. PCPs can lead to stronger ROT (rate of total electron content) variations than other types of ionosphere disturbances. So our observations suggest that the substorms and PCPs, being different types of the high-latitude disturbances, lead to the development of different types and scales of ionospheric irregularities. [ABSTRACT FROM AUTHOR]

In this paper, we discuss the influence of meteorological effects on the data of the ground installation CARPET, which is a detector of the charged component of secondary cosmic rays (CRs). This device is designed in the P.N. Lebedev Physical Institute (LPI, Moscow, Russia) and installed at the Dolgoprudny scientific station (Dolgoprudny, Moscow region; 55.56 ∘ N, 37.3 ∘ E; geomagnetic cutoff rigidity (Rc = 2.12 GV) in 2017. Based on the data obtained in 2019–2020, the barometric and temperature correction coefficients for the CARPET installation were determined. The barometric coefficient was calculated from the data of the barometric pressure sensor included in the installation. To determine the temperature effect, we used the data of upper-air sounding of the atmosphere obtained by the Federal State Budgetary Institution "Central Aerological Observatory" (CAO), also located in Dolgoprudny. Upper-air sounds launch twice a day and can reach an altitude of more than 30 km. [ABSTRACT FROM AUTHOR]

Swarm is ESA's (European Space Agency) first Earth observation constellation mission, which was launched in 2013 to study the geomagnetic field and its temporal evolution. Two Langmuir Probes (LPs) on board of each of the three Swarm satellites provide very accurate measurements of plasma parameters, which contribute to the the study of the ionospheric plasma dynamics. To maintain a high data quality for scientific and operational applications, the Swarm products are continuously monitored and validated via science-oriented diagnostics. This paper presents an overview of the data quality of the Swarm Langmuir Probes' measurements. The data quality is assessed by analysing short and long data segments, where the latter are selected sufficiently long to consider the impact of the solar activity. Langmuir Probes data have been validated through comparison with numerical models, other satellite missions, and ground observations. Based on the outcomes from quality control and validation activities conduced by ESA, as well as scientific analysis and feedback provided by the user community, the Swarm products are regularly upgraded. In this paper we discuss the data quality improvements introduced with the latest baseline, and how the data quality is influenced by the solar cycle. The main anomaly affecting the LP measurements is described, as well as possible improvements to be implemented in future baselines. [ABSTRACT FROM AUTHOR]

The historical magnetic observatory Clementinum operated in Prague from 1839 to 1926. The data from the yearbooks that recorded the observations at Clementinum have recently been digitized and were subsequently converted, in this work, into the physical units of the International System of Units (SI). Introducing a database of geomagnetic data from this historical source is a part of our paper. Some controversial data are also analysed here. In the original historical sources, we identified an error in using the physical units. It was probably introduced by the observers determining the temperature coefficient of the bifilar apparatus. By recalculating the values ​​in the records, some missing values ​​are added; for instance, the temperature coefficients for the bifilar magnetometer, the baselines, and the annual averages for the horizontal intensity in the first years of observations were redetermined. The values ​​of absolute measurements of the declination in 1852, which could not be found in the original sources, were also estimated. The main contribution of this article rests in critically reviewed information about the magnetic observations in Prague, which is, so far, more complete than any other. The work also contributes to the space weather topic by revealing a record of the now almost forgotten magnetic disturbance of 3 September 1839. [ABSTRACT FROM AUTHOR]

The Coimbra Magnetic Observatory (COI), Portugal, established in 1866, has provided nearly continuous records of the geomagnetic field elements for more than 150 years. However, during its long lifetime inevitable changes to the instruments and measurement procedures and even the relocation of the observatory have taken place. In our previous work (Morozova et al., 2014) we performed homogenization – elimination of the artificial changes – of the measured declination series (D) for the period from 1866 to 2006. In this paper we continue work on applying homogenization procedures to the measured series of the absolute monthly values of the horizontal (H , 1866–2006), vertical (Z , 1951–2006) and inclination components (I , 1866–1941). After homogenization of all measured series for the 1866–2006 time interval, we performed the homogenization of the series of all geomagnetic field elements (X , Y , Z , H , D , I and F) to the level of the 2015 epoch. Since all series except D have a gap of about 10 years in the middle of the 20th century, splitting each of them into two, the homogenization to the level of 2015 was done only for the series available after 1951 (with the D series homogenized for the whole time interval of 1866–2015). The COI geomagnetic field elements are available via the following addresses: 10.5281/zenodo.4308022 (Ribeiro et al., 2020) for the original COI data (ASCII and XLSX formats) and 10.5281/zenodo.4308036 (Morozova et al., 2020) for the homogenized COI data (ASCII and XLSX formats). [ABSTRACT FROM AUTHOR]

The QuakeFinder network of magnetometers has recorded geomagnetic field activity in California since 2000. Established as an effort to follow up observations of ULF activity reported from before and after the M =7.1 Loma Prieta earthquake in 1989 by Stanford University, the QuakeFinder network has over 50 sites, fifteen of which are high-resolution QF1005 and QF1007 systems. Pairs of highresolution sites have also been installed in Peru and Taiwan. Increases in pulse activity preceding nearby seismic events are followed by decreases in activity afterwards in the three cases that are discussed here. In addition, longer term data is shown, revealing a rich signal structure not previously known in QuakeFinder data, or by many other authors who have reported on pre-seismic ULF phenomena. These pulses occur as separate ensembles, with demonstrable repeatability and uniqueness across a number of properties such as waveform, angle of arrival, amplitude, and duration. Yet they appear to arrive with exponentially distributed inter-arrival times, which indicates a Poisson process rather than a periodic, i.e., stationary process. These pulses were observed using three-axis induction coil magnetometers that are buried 1--2m under the surface of the Earth. Our sites use a Nyquist frequency of 16 Hertz (25 Hertz for the new QF1007 units), and they record these pulses at amplitudes from 0.1 to 20 nano-Tesla with durations of 0.1 to 12 s. They are predominantly unipolar pulses, which may imply charge migration, and they are stronger in the two horizontal (north-south and east-west) channels than they are in the vertical channels. Pulses have been seen to occur in bursts lasting many hours. The pulses have large amplitudes and study of the three-axis data shows that the amplitude ratios of the pulses taken from pairs of orthogonal coils is stable across the bursts, suggesting a similar source. This paper presents three instances of increases in pulse activity in the 30 days prior to an earthquake, which are each followed by steep declines after the event. The pulses are shown, methods of detecting the pulses and calculating their azimuths is developed and discussed, and then the paper is closed with a brief look at future work. [ABSTRACT FROM AUTHOR]

Electromagnetic phenomena associated with crustal activities have been reported in a wide frequency range (DC-HF). In particular, ULF electromagnetic phenomena are the most promising among them because of the deeper skin depth. However, ULF geoelctromagnetic data are a superposition of signals of different origins. They originated from interactions between the geomagnetic field and the solar wind, leak current by a DC-driven train (train noise), precipitation, and so on. In general, the intensity of electromagnetic signals associated with crustal activity is smaller than the above variations. Therefore, in order to detect a smaller signal, signal discrimination such as noise reduction or identification of noises is very important. In this paper, the singular spectrum analysis (SSA) has been performed to detect the DC-driven train noise in geoelectric potential difference data. The aim of this paper is to develop an effective algorithm for the DC-driven train noise detection. [ABSTRACT FROM AUTHOR]

Wireless capsule endoscopy is an established medical application for the examination of the gastrointestinal tract. However, the robust and precise localization of these capsules is still in need of further scientific investigation. This paper presents an innovative differential magnetic localization method for capsule endoscopy to prevent interference caused by the geomagnetic field. The effect of changing the orientation of the capsule on the localization process was also examined. Simulations using COMSOL Multiphysics with the superimposed geomagnetic field were performed. The Levenberg–Marquardt algorithm was applied in MATLAB to estimate the position and orientation of the capsule. Comparing the proposed differential method with the absolute magnetic localization method under ideal conditions, the mean position and orientation errors were reduced by three orders in magnitude to less than 0.1 mm and 0.1 ∘ respectively. Even if sensor non-idealities are considered, the simulation-based results reveal that our proposed method is competitive with state-of-the-art geomagnetic compensation methods for static magnetic localization of capsule endoscopes. The achieved localization accuracy by applying the differential method is not dependent on the rotation of the localization system relative to the geomagnetic flux density under the made assumptions and the impact of the magnet orientation is neglectable. It is concluded that the proposed method is capable of preventing all interference whose components are approximately equal at all sensors with identical orientation. [ABSTRACT FROM AUTHOR]

In our previous papers we have shown that the fractal (monofractal) dimension (Do) showed a significant increase before the Guam earthquake occurred on 8 August, 1993. In order to have a further support to this precursory effect to the general rupture (earthquake) we have carried out the corresponding multifractal analysis (by means of detrended fluctuation analysis) for the same data to study the statistical self-similar properties in a wide range of scales. We have analyzed the ULF geomagnetic data (the most intense H component) observed at Guam observatory. As the result, we have found that we could observe significant changes in the multifractal parameters at Guam such that αmin showed a meaningful decrease about 25 days before the earthquake and correspondingly δalpha; increased because αmax exhibited no significant change at all. The most sensitive parameter seems to be non-uniformity factor δ. Correspondingly, the generalized multifractal dimension Dq (q>1) showed a significant decrease (whereas Dq (q<0) showed no change) and D0 (=Dq (q=0) (as already found in our previous papers) is reconfirmed to increase before the earthquake. These multifractal characteristics seem to be a further support that these changes are closely associated with the earthquake as a precursor to the Guam earthquake, providing us with appreciable information on the pre-rupture evolution of the earthquake. [ABSTRACT FROM AUTHOR]

This paper proposes a new method to evaluate geomagnetic activity based on wavelet analysis during the solar minimum activity (2007). In order to accomplish this task, a newly developed algorithm called effectiveness wavelet coefficient (EWC) was applied. Furthermore, a comparison between the 5 geomagnetically quiet days determined by the Kp-based method and by wavelet-based method was performed. This paper provides a new insight since the geomagnetic activity indexes are mostly designed to quantify the extent of disturbance rather than the quietness. The results suggest that the EWC can be used as an alternative tool to accurately detect quiet days, and consequently, it can also be used as an alternative to determine the Sq baseline to the current Kp-based 5 quietest days method. Another important aspect of this paper is that most of the quietest local wavelet candidate days occurred in an interval 2 days prior to the high-speed-stream-driven storm events. In other words, the EWC algorithm may potentially be used to detect the quietest magnetic activity that tends to occur just before the arrival of high-speed-stream-driven storms. [ABSTRACT FROM AUTHOR]

On timescales longer than the solar cycle, long-term changes in CO2 concentration and geomagnetic field have the potential to affect thermospheric dynamics. In this paper, we investigate the thermospheric dynamical response to these two factors during the Holocene, using two sets of ~12,000-yr control runs by the coupled thermosphere-ionosphere model, GCITEM-IGGCAS. The main results indicate that increased/decreased CO2 will enhance/weaken the thermospheric circulation throughout the Holocene, but this effect is nonlinear. The cooling effect of CO2 in the thermosphere further provides plausible conditions for atmospheric tidal propagation and increases the thermospheric tidal amplitude. Geomagnetic variations induce hemispheric asymmetrical responses in the thermospheric circulation. Large changes in the circulation occur at high latitudes in the hemisphere with distant magnetic poles drift, inferring a crucial role of geomagnetic non-dipole variations in circulation changes. A positive correlation between the diurnal migrating tide (DW1) and geomagnetic dipole moment is revealed for the first time. The amplitude of DW1 in temperature will increase by ~1–3 K for each 1×1022 Am2 increase in dipole moment. [ABSTRACT FROM AUTHOR]

This work focuses on the progress of space weather monitoring in Pakistan. Pakistan's first geomagnetic observatory was established in Quetta in 1953. However, the beginning of what we would now call space weather services on a formal level took place in 1971, when the national space agency, the Pakistan Space and Upper Atmosphere Research Commission (SUPARCO), established the country's first ionospheric station. Later, in 1983, a geomagnetic observatory was set up in Karachi with the aim of providing high frequency (HF) support and geomagnetic storm alerts to relevant users. With the progression of time, nations began to prioritize space weather monitoring to ensure the safety and security of technological assets. Therefore, it was considered imperative to upgrade the array of instruments in order to maintain the reliability of operations and the efficient utilization of data to contribute to research at local, regional and global scales. Pakistan has recently established a dedicated space weather monitoring facility known as the Pakistan Space Weather Centre (PSWC). This paper describes the historic evolution of space weather infrastructure in Pakistan and the current contribution of the PSWC. [ABSTRACT FROM AUTHOR]

The present paper studies the perturbations in an equatorial ionization anomaly (EIA) region during the Southern Hemisphere (SH) sudden stratospheric warming (SSW) of 2002, using the location of EIA crests derived from global positioning system (GPS) station observations, the total electron content (TEC) obtained by the International GNSS (global navigation satellite system) Service (IGS) global ionospheric TEC map (GIMs) and the equatorial electrojet (EEJ) estimated by the geomagnetic field in the Asian sector. The results indicate the existence of an obvious quasi-10 d periodic oscillation in the location and TEC of the northern and southern EIA crest. An eastward phase progression of the quasi-10 d wave producing the SH SSW of 2002 is also identified in polar stratospheric temperature. Previous studies have shown that a strong quasi-10 d planetary wave with zonal wave numbers s=1 extended from the lower stratosphere to the mesosphere and lower thermosphere during the SH SSW of 2002 (Palo et al., 2005). Moreover, the EEJ driven by the equatorial zonal electric field exhibits quasi-10 d oscillation, suggesting the enhanced quasi-10 d planetary wave associated with SSW penetrates into the ionosphere E region and produces oscillation in the EIA region through modulating the E-region electric fields. Our results reveal some newer features of ionospheric variation that have not been reported during Northern Hemisphere (NH) SSWs. [ABSTRACT FROM AUTHOR]

Studying the access of the cosmic rays (CRs) into the magnetosphere is important to understand the coupling between the magnetosphere and the solar wind. In this paper we numerically studied CRs' magnetospheric access with vertical geomagnetic cutoff rigidities using the method proposed by Smart and Shea (1999). By the study of CRs' vertical geomagnetic cutoff rigidities at high latitudes we obtain the CRs' window (CRW) whose boundary is determined when the vertical geomagnetic cutoff rigidities drop to a value lower than a threshold value. Furthermore, we studied the area of CRWs and found out they are sensitive to different parameters, such as the z component of interplanetary magnetic field (IMF), the solar wind dynamic pressure, AE index, and Dst index. It was found that both the AE index and Dst index have a strong correlation with the area of CRWs during strong geomagnetic storms. However, during the medium storms, only AE index has a strong correlation with the area of CRWs, while Dst index has a much weaker correlation with the area of CRWs. This result on the CRW can be used for forecasting the variation of the cosmic rays during the geomagnetic storms. [ABSTRACT FROM AUTHOR]

Among the lithospheric, atmospheric and ionospheric earthquake precursors, it seems that the ionospheric anomalies showing a meaningful association with seismic activities during absence of solar and geomagnetic activities. Unfortunately there are a limited number of satellite sensors to survey the ionosphere and study on seismo-ionospheric anomalies. This paper represents the data analysis results of Swarm satellites including Alpha, Bravo and Charlie data around the Mexico (September 8, 2017) earthquake. The orbital analysis and time series of magnetic field parameters (magnetic scalar and vectors (X, Y, Z) components) inside the Dobrovolsky's area show anomalous variations close to the time and locations of the Mexico earthquake. There is a concavity or convexity variations in the some of the time-series to the centre of the earthquake day. In other words, from about 90 days before the event a decreasing or increasing trend in variations of parameters is observed and exactly after the earthquake day its trend changes. It should be noted that the variations of the solar and geomagnetic indices must indicate a normal behaviour during the observed seismo-ionospheric anomalies. Therefore this study indicates that the Swarm satellites measurements play an undeniable role in progress the studies of the ionospheric precursors. [ABSTRACT FROM AUTHOR]

Short-term upper atmosphere variations due to magnetospheric forcing are very complex, and neither well understood nor capably modeled due to limited observations. In this paper, mass density variations from 10 years of GRACE observations (2003–2013) are isolated via the parameterization of annual, local solar time (LST), and solar cycle fluctuations using a principal component analysis (PCA) technique. The resulting residual disturbances are investigated in terms of magnetospheric drivers. The magnitude of high-frequency (δ < 10 d) disturbances reveals unexpected dependencies on the solar cycle, seasonal, and an asymmetric behavior with smaller amplitudes in June in the south polar region (SPR). This seasonal modulation might be related to the Russell–McPherron (RM) effect. Meanwhile, we find a similar pattern, although less pronounced, in the northern and equatorial regions. A possible cause of this latitudinal asymmetry might be the irregular shape of the Earth's magnetic field (with the north dip pole close to Earth's rotation axis, and the south dip pole far from that axis). After accounting for the solar cycle and seasonal dependencies by regression analysis to the magnitude of the high-frequency perturbations, the parameterization in terms of the disturbance geomagnetic storm-time index Dst shows the best correlation, whereas the geomagnetic variation Am index and merging electric field Em are the best predictors in terms of time delay. We test several mass density models, including JB2008, NRLMSISE-00, and TIEGCM, and find that they are unable to completely reproduce the seasonal and solar cycle trends found in this study, and show a clear overestimation of about 100 % during low solar activity periods. [ABSTRACT FROM AUTHOR]

A method for the combined processing measurements of the projections and the absolute magnitudes of geomagnetic field intensity vectors, based on mathematical technology of local approximation models, is proposed. The approach realized in this paper, based on the proposed method, provides an increase in quality of the measurements of the projections of the geomagnetic intensity vector. An algorithm for the two-stage combined processing of the measurements of projections and absolute magnitudes of geomagnetic field intensity vectors is developed. The operation of the combined processing algorithm was tested on models and observatory measurements. The estimates of the combined processing algorithm errors were obtained using statistical modelling. The reduction of the root-mean-square error values was achieved for the estimates of the projections of geomagnetic field intensity vectors. [ABSTRACT FROM AUTHOR]

The System for Automated Geoscientific Analyses (SAGA) is an open source geographic information system (GIS), mainly licensed under the GNU General Public License. Since its first release in 2004, SAGA has rapidly developed from a specialized tool for digital terrain analysis to a comprehensive and globally established GIS platform for scientific analysis and modeling. SAGA is coded in C++ in an object oriented design and runs under several operating systems including Windows and Linux. Key functional features of the modular software architecture comprise an application programming interface for the development and implementation of new geoscientific methods, a user friendly graphical user interface with many visualization options, a command line interpreter, and interfaces to interpreted languages like R and Python. The current version 2.1.4 offers more than 600 tools, which are implemented in dynamically loadable libraries or shared objects and represent the broad scopes of SAGA in numerous fields of geoscientific endeavor and beyond. In this paper, we inform about the system's architecture, functionality, and its current state of development and implementation. Furthermore, we highlight the wide spectrum of scientific applications of SAGA in a review of published studies, with special emphasis on the core application areas digital terrain analysis, geomorphology, soil science, climatology and meteorology, as well as remote sensing. [ABSTRACT FROM AUTHOR]

The International Union of Geodesy and Geophysics (IUGG) was established in 1919 to promote activities of already-existing international scientific societies dealing with geodesy, terrestrial magnetism and electricity, meteorology, physical oceanography, seismology, and volcanology. At the first General Assembly a Section of scientific hydrology was added, making a total of seven Sections of the Union. This paper introduces IUGG by presenting its current mission, structure, partners, and programs; discussing various international geophysical efforts before its origin; and describing the Union's development from the end of World War I to the beginning of World War II. During this period (1919–1939), the number of member countries increased from the 9 founding Member countries to 35; seven General Assemblies were held, each in a different international venue; and the number of delegates attending the assemblies increased from a few dozen to more than 800 scientists. At the Fifth General Assembly in 1933, the term "section" was replaced by "international association". Each General Assembly of the Union, since the First General Assembly in Rome, Italy, in 1922 to the VII General Assembly in Washington, DC, USA, in 1939, is summarized, and the distinguished scientists who contributed to the Union's formation and it early development are introduced. [ABSTRACT FROM AUTHOR]

Ionospheric tomography based on the total electron content (TEC) data along the ray path from Global Navigation Satellite Systems (GNSS) satellites to ground receivers is a typical ill-posed inverse problem. The regularization method is an effective method to solve this problem, which incorporates prior constraints to approximate the real ionospheric variations. When two or more prior constraints are used, the corresponding multiple regularization parameters are introduced in the cost functional. Assuming that the ionospheric spatial variations can be separable in the horizontal and vertical directions, different prior constraints are used in each direction, and the dual-parameter regularization algorithm is established to reconstruct the three-dimensional ionospheric electron density in the present paper. To make the reconstruction results comprehensively reflect the observation information and background (prior) information, it is crucial to determine the optimal regularization parameters. The linear model function method is used to choose these regularization parameters. Both an ideal test and a real test show that this regularization algorithm can effectively improve the background model output. [ABSTRACT FROM AUTHOR]

In this paper a brief summary will be given about the historical development of geomagnetism as a science in southern Africa and particularly the role played by Hermanus Magnetic Observatory in this regard. From a very modest beginning in 1841 as a recording station at the Cape of Good Hope, Hermanus Magnetic Observatory is today part of the South African National Space Agency (SANSA), where its geomagnetic field data are extensively used in international research projects ranging from the physics of the geo-dynamo to studies of the near-Earth space environment. [ABSTRACT FROM AUTHOR]

This paper presents a statistical study of the equatorward boundary of small-scale field-aligned currents (SSFACs) and investigates the relation between this boundary and the plasmapause (PP). The PP data used for validation were derived from in situ electron density observations of NASA's Van Allen Probes. We confirmed the findings of a previous study by the same authors obtained from the observations of the CHAMP satellite SSFAC and the NASA IMAGE satellite PP detections, namely that the two boundaries respond similarly to changes in geomagnetic activity, and they are closely located in the near midnight MLT sector, suggesting a dynamic linkage. Dayside PP correlates with the delayed time history of the SSFAC boundary. We interpreted this behaviour as a direct consequence of co-rotation: the new PP, formed on the night side, propagates to the dayside by rotating with Earth. This finding paves the way toward an efficient PP monitoring tool based on an SSFAC index derived from vector magnetic field observations at low-Earth orbit. [ABSTRACT FROM AUTHOR]

Electromagnetic phenomena observed in association with increases in seismic activity have been studied for several decades. These phenomena are generated during the precursory phases of an earthquake as well as during the main event. Their occurrence during the precursory phases may be used in short-term prediction of a large earthquake. In this paper, we examine ultra-low frequency (ULF) electric field data from the DEMETER satellite during the period leading up to the Sichuan earthquake. It is shown that there is an increase in ULF wave activity observed as DEMETER passes in the vicinity of the earthquake epicentre. This increase is most obvious at lower frequencies. Examination of the ULF spectra shows the possible occurrence of geomagnetic pearl pulsations, resulting from the passage of atmospheric gravity waves generated in the vicinity of the earthquake epicentre. [ABSTRACT FROM AUTHOR]

Using ULF (ultra low frequency) measurements of magnetometer and ICE (Instrument Champ Electrique) experiments on board the DEMETER satellite, possible irregularities in ULF magnetic and electric components have been surveyed in the vicinity of Samoa (29 September 2009) earthquake region. The data used in this paper cover the period from 1 August 2009 to 11 October 2009. The anomalous variations in magnetic components (Bx, By and Bz) were clearly observed on 1 and 3 days before the event. It is seen that the periodic patterns of the magnetic components obviously changed prior to the earthquake. These unusual variations have been also observed in the variations of polarization index obtained from the magnetic components during the whole period at ~10:30 and ~22:30 LT. It is concluded that the polarization exhibits an apparent increase on 1 and 3 days preceding the earthquake. These observed unusual disturbances in ULF magnetic components were acknowledged using the detected perturbations in ULF electric components (Ex, Ey and Ez) in the geomagnetic coordinate system. Finally, the results reported in this paper were compared with previous results for this Samoa earthquake. Hence, the detected anomalies resulting from the magnetometer and ICE ULF waveforms in quiet geomagnetic conditions could be regarded as seismo-ionospheric precursors. [ABSTRACT FROM AUTHOR]

A new type of the series of quasi-periodic (QP) very low frequency (VLF) emissions in frequency range of 1-5 kHz, and not associated with geomagnetic pulsations, has been discovered at auroral latitudes (L= 5.3) during the Finnish VLF campaign (held in December 2011). At least five unusually spectacular events, each with a duration of several hours, have been observed during the night under conditions of quiet geomagnetic activity (Kp = 0-1), although QPs usually occur during the daytime. Contrary to the QP emissions typically occurring during the day, the spectral structure of these QP events represented an extended, complicated sequence of repeated discrete rising VLF signals. Their duration was about 2-3 min each, with the repetition periods ranging from ∼1 min to ∼10 min. Two such nighttime nontypical events are reported in this paper. The fine structure of the separated QP elements may represent a mixture of the different frequency band signals, which seem to have independent origins. It was found that the periodic signals with lower frequency appear to trigger the strong dispersive upper frequency signals. The temporal dynamics of the spectral structure of the QPs studied were significantly controlled by some disturbances in the solar wind and interplanetary magnetic field (IMF). This finding is very important for future theoretical investigations because the generation mechanism of this new type of QP emissions is not yet understood. [ABSTRACT FROM AUTHOR]

The geomagnetic observatory of Juriquilla Mexico, located at longitude -100.45° and latitude 20.70°, and 1946ma.s.l., has been operational since June 2004 compiling geomagnetic field measurements with a three component fluxgate magnetometer. In this paper, the results of the analysis of these measurements in relation to important seismic activity in the period of 2007 to 2009 are presented. For this purpose, we used superposed epochs of Discrete Wavelet Transform of filtered signals for the three components of the geomagnetic field during relative seismic calm, and it was compared with seismic events of magnitudes greater than Ms > 5.5, which have occurred in Mexico. The analysed epochs consisted of 18 h of observations for a dataset corresponding to 18 different earthquakes (EQs). The time series were processed for a period of 9 h prior to and 9 h after each seismic event. This data processing was compared with the same number of observations during a seismic calm. The proposed methodology proved to be an efficient tool to detect signals associated with seismic activity, especially when the seismic events occur in a distance (D) from the observatory to the EQ, such that the ratio D/ρ <1.8 where ρ is the earthquake radius preparation zone. The methodology presented herein shows important anomalies in the Ultra Low Frequency Range (ULF; 0.005-1 Hz), primarily for 0.25 to 0.5 Hz. Furthermore, the time variance (σ2) increases prior to, during and after the seismic event in relation to the coefficient D1 obtained, principally in the Bx (N-S) and By (E-W) geomagnetic components. Therefore, this paper proposes and develops a new methodology to extract the abnormal signals of the geomagnetic anomalies related to different stages of the EQs. [ABSTRACT FROM AUTHOR]

During the last twenty years a time-synchronized network of magnetometers has operated in Central Italy along the Apennine chain to monitor the magnetic field anomalies eventually related to the tectonic activity. At present time the network consists of five stations. In the past only few anomalies in the local geomagnetic field, possibly associated to earthquakes, has been observed, not least because the network area has shown a low-moderate seismic activity with the epicentres of the few events with Ml≥5 located away from the network station. During 2007 two Ml≈4 earthquakes occurred in proximity of two stations of the network. Here we report the magnetic anomalies in the geomagnetic field that could be related with these tectonic events. To better investigate these two events a study of ULF (ultra-low-frequency) emissions has been carried out on the geomagnetic field components H, D, and Z measured in L'Aquila Observatory during the period from January 2006 to December 2008. We want to stress that this paper refers to the period before the 2009 L'Aquila seismic sequence which main shock (Ml=5.8) of 6 April heavily damaged the medieval centre of the city and surroundings. At present time the analysis of the 2009 data is in progress. [ABSTRACT FROM AUTHOR]

In this paper we give firstly a broad review of the space plasma turbulence around the ion characteristic space and temporal scales within two natural laboratories, the solar wind and the Earth magnetosheath. In both regions power law spectra of magnetic fluctuations are observed. In both regions these spectra have a break in the vicinity of the ion cyclotron frequency. A distinctive feature of the magnetosheath turbulence is the presence of Alfvén vortices at scales of the spectral break. The Alfvén vortices are multi-scale nonlinear structures. We give a review of the main theoretical features of incompressible Alfvén vortsices in the second part of the paper. Finally, we analyze the spectral properties of the Alfvén vortex solution and of the network of such vortices. We show that the observed magnetosheath spectrum in presence of the Alfvén vortices can be described, at least partially, by the vortex network model. [ABSTRACT FROM AUTHOR]