Geomagnetic Elements Research Articles

Hardware Design and Implementation of a High-Precision Optically Pumped Cesium Magnetometer System Based on the Human-Occupied Vehicle Platform

High-precision magnetometers play a crucial role in ocean exploration, geophysical prospecting, and military and security applications. Installing them on human-occupied vehicle (HOV) platforms can greatly enhance ocean exploration capabilities and efficiency. However, most existing magnetometers suffer from low sensitivity and excessively large size. This study presents a high-sensitivity, miniaturized magnetometer based on cesium optically pumped probes. The designed magnetometer utilizes a three-probe design to eliminate the detection dead zone of the cesium optically pumped probe and enable three-dimensional magnetic detection. The proposed magnetometer uses a flux gate probe to detect the three-axis magnetic field and ensure that the probe does not enter the dead zone. The three probes can automatically switch by measuring the geomagnetic elements and real-time attitude of the HOV platform. This article primarily introduces the cesium three-probe optically pump, flux gate sensor, and automatic switching scheme design of the above-mentioned magnetometer. Moreover, it is proven through testing that the core indicators, such as the accuracy and sensitivity of the cesium three-probe optically pumped and flux gate sensor, reach international standards. Finally, the effectiveness of the automatic switching scheme proposed in this study is demonstrated through drone-mounted experiments.

COMPORTAMIENTO SECULAR EN LOS DATOS GEOMAGNÉTICOS DE LOS OBSERVATORIOS PERMANENTES DE ARGENTINA

The secular variation of the geomagnetic field is the temporal variation that takes place in the field on time scales between few years to hundreds or thousands of years. On the other hand, impulses or ”geomagnetic jerks” indicate a rapid change in the slope of the secular variation. The origin of these phenomena is linked to the behavior of the geodynamo and the contribution of the outer mantle-core interaction.ROMP (acronym from spanish “ Red de Observatorios Magnéticos Permanentes”) is composed by the following observatories: ”Las Acacias ”(LAS) at Buenos Aires,” Trelew ”(TRW) at Chubut,” Pilar ”(PIL) at Córdoba and ”Orcadas”(ORC) at the Argentine sector in Antartic; the first two depend on the National University of La Plata and the latter on the National Meteorological Service. In the present work one analyzes the secular variation and the determination of jerks in the geomagnetic elements recorded at the ROMP stations, in historical times up to the present.

INVESTIGATING THE VARIATIONS OF HORIZONTAL (H) AND VERTICAL (Z) COMPONENTS OF THE GEOMAGNETIC FIELD AT SOME EQUATORIAL ELECTROJET STATIONS

This research is monitoring equatorial geomagnetic current which causes atmospheric instabilities and affects high frequency and satellite communication. It presents the variations of Horizontal (H) and vertical (Z) component of the geomagnetic field at some Equatorial Electrojet (EEJ) Stations during quiet days. Data from five (5) observatories along the magnetic equator were used for the study. Daily baseline values for each of the geomagnetic element 𝐻 and Z were obtained. The monthly average of the diurnal variation and the seasonal variations were found. Results showed that the variations of the geomagnetic element of both H and Z differ in magnitudes from one stations to another along the geomagnetic Equator due to the differences of their geomagnetic latitude. The Amplitude curves for Z) are seen to be conspicuously opposite to that of H), and there is absence of CEJ in Z- Component but present in H- Components. The values during the pre-sunrise hours are low compare to daytime hours. Minimum variations of dH was observed during June solstice and maximum variations was observed during Equinox season. This study shows that daily variations of (H) and (Z) occur in all the stations. The enhancement in H is as a result of EEJ current

THE STUDY OF LONGITUDINAL AND LATITUDINAL VARIATION OF EQUATORIAL ELECTROJET SIGNATURE AT STATIONS WITHIN THE 96°MM AND 210°MM AFRICAN AND ASIAN SECTORS RESPECTIVELY UNDER QUIET CONDITIONS.

Solar quiet current (S_q) and Equatorial Electrojet (EEJ) are two current systems which are produced by electric current in the ionosphere. The enhancement of the horizontal magnetic field is the EEJ. This research is needed for monitoring equatorial geomagnetic current which causes atmospheric instabilities and affects high frequency and satellite communication. This study presents the longitudinal and latitudinal variation of equatorial electrojet signature at stations within the 96°mm and 210°mm African and Asian sectors respectively during quiet condition. Data from eleven observatories were used for this study. The objectives was to determine the longitudinal and latitudinal geomagnetic field variations during solar quiet conditions, Investigate monthly variation and diurnal transient seasonal variation; Measure the strength of the EEJ at stations within the same longitudinal sectors and find out the factors responsible for the longitudinal and latitudinal variation of EEJ. Horizontal (H) component of geomagnetic field for the year 2008 from Magnetic Data Acquisition System (MAGDAS) network were used for the study. The International Quiet Days (IQDs) were used to identify quiet days. Daily baseline values for each of the geomagnetic element H were obtained. The monthly average of the diurnal variation was found. The seasonal variation of dH was found. Results showed that: The longitudinal and latitudinal variation in the dH differs in magnitude from one station to another within the same longitude due to the difference in the influence of the EEJ on them.

INVESTIGATING THE VARIATIONS OF HORIZONTAL (H) AND VERTICAL (Z) COMPONENTS OF THE GEOMAGNETIC FIELD AT SOME EQUATORIAL ELECTROJET STATIONS

This research is monitoring equatorial geomagnetic current which causes atmospheric instabilities and affects high frequency and satellite communication. It presents the variations of Horizontal (H) and vertical (Z) component of the geomagnetic field at some Equatorial Electrojet (EEJ) Stations during quiet days. Data from five (5) observatories along the magnetic equator were used for the study. Daily baseline values for each of the geomagnetic element 𝐻 and Z were obtained. The monthly average of the diurnal variation and the seasonal variations were found. Results showed that the variations of the geomagnetic element of both H and Z differ in magnitudes from one stations to another along the geomagnetic Equator due to the differences of their geomagnetic latitude. The Amplitude curves for Z) are seen to be conspicuously opposite to that of H), and there is absence of CEJ in Z- Component but present in H- Components. The values during the pre-sunrise hours are low compare to daytime hours. Minimum variations of dH was observed during June solstice and maximum variations was observed during Equinox season. This study shows that daily variations of (H) and (Z) occur in all the stations. The enhancement in H is as a result of EEJ current.

A novel geomagnetic assimilation method of vector geomagnetic data

Geomagnetic field has important applications in Earth Science, earthquake prediction, aerospace, national defense construction and other areas. Therefore, accurate modeling of regional geomagnetic field is very important. Geomagnetic assimilation method can effectively improve the accuracy of regional vector geomagnetic data, and then promote the establishment of high-precision geomagnetic regional model. The geomagnetic stations at different latitudes and longitudes have different influences on the geomagnetic assimilation of vector geomagnetic data. However, traditional geomagnetic assimilation methods do not take into account the differences in latitude and longitude, which result in low accuracy of the geomagnetic assimilation of vector geomagnetic data. To solve the problem, this paper proposes a new geomagnetic assimilation method based on the three weighting factors of direction, distance and a parameter k. In this method, the longitude differences and latitude differences of different stations are taken as the weight elements to participate in the weight determination, and parameter k is set to further modify the weight, so as to achieve the high precision geomagnetic assimilation to regional vector geomagnetic data. Based on the real observation data of five stations in the European region of station network in the world data center (WDC), this paper conducted geomagnetic assimilation of the vector geomagnetic data of different stations. The experimental results show that at five stations which include some central stations and some marginal stations, for the F, H, D and I geomagnetic elements, the geomagnetic assimilation accuracy of the proposed method is better than that of the method based on the distance weighting method both on magnetically quiet day and on magnetically disturbed day. In addition, the results also show that the geomagnetic assimilation accuracy of FUR station, which is a marginal station, is significantly improved by the proposed method. On magnetically disturbed day, the error of F component is reduced by 0.6 nT, and the error of H component is reduced by 1 nT. On magnetically quiet day, the error of F component is reduced by 0.4 nT, and the error of H component is reduced by 0.1 nT. The above results prove the effectiveness and feasibility of the proposed method in the geomagnetic assimilation of vector geomagnetic data, especially for the vector geomagnetic data of marginal area.

SCHA.DIF.4k: 4,000 Years of Paleomagnetic Reconstruction for Europe and Its Application for Dating

AbstractSince the publication of the European archaeomagnetic field model SCHA.DIF.3k in 2009, the number of paleomagnetic data derived from archaeological materials such as baked clays and volcanic rocks coming from Europe has increased by about 90% for directions and around 180% for intensities. Taking advantage of this increase, here we provide an updated regional archaeomagnetic model, called SCHA.DIF.4k, for the European continent and adjacent areas and now covering the last four millennia. To model the three geomagnetic elements, declination, inclination, and intensity, we use the regional R‐SCHA2D technique in space and temporal basis of cubic splines. A critical selection of the archaeomagnetic and volcanic data available in a spherical cap of 30° centered at 40°N latitude and 10°E longitude has been considered. In addition, in order to better constrain the behavior of the archaeomagnetic field during the last centuries, we include the historical data of the HISTMAG compilation. The new regional model allows us to better define the paleomagnetic field over Europe as well as to generate new paleosecular variation curves for archaeomagnetic dating purposes. Using these curves, the dating precision has been estimated for the last 4 kyr. As expected, results show that it strongly depends on the data uncertainties, the temporal data distribution and the behavior of the geomagnetic field itself. In addition, the use of the full vector geomagnetic field, instead of the directional information exclusively, provides more precise archaeomagnetic dating results.

Прогнозування локальних геомагнітних збурень на прикладі даних магнітної обсерваторії «Львів»

For the first time in world practice, predictive models were constructed for X, Y, Z geomagnetic elements. Based on these models, the prediction was made with 3 hours lead time using data of the “Lviv” magnetic observatory. The properties of models are as follows: observatory — LVV, рredicted values — XYZ; lead time — 3 hours; correlation coefficients’ averaged measurement data — 0.824 (X), 0.811 (Y), 0.804 (Z); prediction efficiency — 0.816 (X), 0.803 (Y), 0.801 (Z); skill score — 0.115 (X), 0.095 (Y), 0.099 (Z). The developed models were tested in the Main Center of Special Monitoring, and they were found to meet the Basic Requirements for operational predictive models.

Unstable spatial differences of the geomagnetic elements caused by changing water saturation of a volcanic sediment

Since the beginning of geomagnetic recording at Tihany Geophysical Observatory, baseline instability has been observed, especially in the case of the old variation house. The regularly observed annual baseline change is independent from the type of magnetometer. Common environmental effects on the instruments (for example temperature effects) are not suitable to characterize this variation. A possible reason of this instability is an unconventional geomagnetic effect on the magnetic properties of the sediment. The water saturation of a lake mud in a geyser cone shows correspondence with the variation of the base values. X-ray powder diffraction measurement detected goethite in the lake mud which, in fact makes possible the appearance of a super-ferromagnetic effect on goethite. In this study we present a possible source and the mechanism of the effect.

Magnetic Data Acquisition System (MAGDAS) Malaysia: installation and preliminary data analysis at ESERI, UNISZA

Magnetic Data Acquisition System (MAGDAS) is a magnetometer initiated by the International Center for Space Weather Science and Education in Kyushu University, Japan, to study space weather. The latest of real-time Magnetic Data Acquisition System/Circum-pan Pacific Magnetometer Network was successfully installed at the East Coast Environmental Research Institute in Universiti Sultan Zainal Abidin, Terengganu, Malaysia, by Kyushu University. This is the fifth magnetometer under the MAGDAS network (geographic latitude and longitude: 5.23°, 103.04° and geomagnetic latitude and longitude: − 4.21°, 175.91°). In this study, the results of data plot obtained at Terengganu (TRE) station were shown to have reliable patterns of geomagnetic elements. The amplitude variations for each component were also proximate with other stations and a standard model. This study compared MAGDAS-II data for the H component with solar wind data (input energy, IMF, dynamic pressure and speed).

The Egyptian geomagnetic reference field to the Epoch, 2010.0

The present work is a compilation of two tasks within the frame of the project “Geomagnetic Survey & Detailed Geomagnetic Measurements within the Egyptian Territory” funded by the “Science and Technology Development Fund agency (STDF)”. The National Research Institute of Astronomy and Geophysics (NRIAG), has conducted a new extensive land geomagnetic survey that covers the whole Egyptian territory. The field measurements have been done at 3212 points along all the asphalted roads, defined tracks, and ill-defined tracks in Egypt; with total length of 11,586km. In the present work, the measurements cover for the first time new areas as: the southern eastern borders of Egypt including Halayeb and Shlatin, the Quattara depresion in the western desert, and the new roads between Farafra and Baharia oasis. Also marine geomagnetic survey have been applied for the first time in Naser lake.Misallat and Abu-Simble geomagnetic observatories have been used to reduce the field data to the Epoch 2010. During the field measurements, whenever possible, the old stations occupied by the previous observers have been re-occupied to determine the secular variations at these points.The geomagnetic anomaly maps, the normal geomagnetic field maps with their corresponding secular variation maps, the normal geomagnetic field equations of the geomagnetic elements (EGRF) and their corresponding secular variations equations, are outlined. The anomalous sites, as discovered from the anomaly maps are, only, mentioned. In addition, a correlation between the International Geomagnetic Reference Field (IGRF) 2010.0 and the Egyptian Geomagnetic Reference Field (EGRF) 2010 is indicated.

Report on the magnetic survey in Slovakia for the 2014.5 epoch

Abstract The models of the distribution of the elements of the geomagnetic field must be updated regularly. For this purpose geomagnetic measurements have to be carried out repeatedly at geomagnetic observatories as well as at temporary observation points. In this paper the results of the geomagnetic survey that was carried out in Slovakia in the year 2014 are presented. The measurements were performed at 12 observation points and they were reduced to the 2014.5 epoch. The secular variation between 2007.5 and 2014.5 was also calculated. The obtained values of the geomagnetic elements were used for calculating a 1st-degree polynomial model for the distribution of magnetic declination, inclination and total field. The comparison with the IGRF model showed that the polynomial model provided more accurate results for magnetic inclination and total field. For magnetic declination, on the contrary, the IGRF model produced slightly better results than the polynomial model.

Colaba–Alibag magnetic observatory and Nanabhoy Moos: the influence of one over the other

Abstract. The first permanent magnetic observatories in colonial India were established by the East India Company and under the Göttingen Magnetic Union. One of the world's longest running observatories was set up at Colaba (Bombay) in 1841, which was shifted to Alibag in 1904 to avoid electric traction effects on magnetic recordings. The observatory is located at the northwestern tip of Maharashtra, India, on the Arabian Sea. The magnetic data at Colaba were collected through eye-observation instruments from 1841 to 1872 and by photographic (magnetograph) instruments from 1872 to 1905, which reveal seasonal and other periodic effects on geomagnetic elements. Seasonal influence can be deciphered on the H minimum, but not on the maximum; the disturbances in March and April were opposite to those in December and January. D was maximum in 1880 (57' E) and minimum in 1904 (10' E). The data from 1882 to 1905 revealed that H annual inequality was influenced by 5.5-year periodicity, D by 13.5 days from 1888 to 1905, and I and Z by 11-year periodicity from 1894 to 1905 and 1873 to 1905, respectively. Secular variation of Z was parallel to that of I. Z exhibited an increasing trend from 1868 (12 874 nT) to 1905 (15 083 nT). The plan and location of Colaba–Alibag as well as the instruments used are discussed. The initial Colaba magnetic data containing "magnetic disturbances" was harnessed to identify the "disturbing point" on Earth. Nanabhoy Moos, the first Indian director, presciently hinted at a solar origin for magnetic disturbances, revealed the dependence of magnetic elements on the sunspot cycle, unraveled disturbance daily variation, and tried to understand the association, if any, between geomagnetic, seismological and meteorological phenomena. The two giant volumes published in 1910 attest to Moos' seminal work and his inventiveness in organizing and analyzing long series data. He also had a major role in moving Colaba magnetic observatory to Alibag. Thus, the observatory and Moos had a synergestic relationship influencing each other. The long data series has as much historical significance as scientific, which can bring out short- as well as long-term trends in geomagnetic data.

Extended and revised archaeomagnetic database and secular variation curves from Bulgaria for the last eight millennia

The efforts of geophysicists to describe geomagnetic field behaviour in the past lead to creation of different geomagnetic field models. On the other hand, the established regional palaeosecular variations of geomagnetic elements are increasingly used for dating purposes in archaeology. Both of these goals can be achieved if sufficient amounts of long archaeomagnetic data sets exist for different geographical regions. The accumulation of archaeomagnetic determinations began at the middle of the last century, parallel with the progressive development of experimental methodology and acceptance criteria. The presence of great number of old determinations requires their critical assessment. The important question about the reliability of the associated dating intervals should be also re-assessed. All this requires the continuous refinement and extension of the accumulated databases. This paper presents the last synthesis of Bulgarian archaeomagnetic database and the local palaeosecular variation curves obtained using a statistical treatment based on Bayesian approach (RenCurve software). The rock-magnetic characteristics of the newly included, non-published results are summarized.

Correction of artificial jumps in the historical geomagnetic measurements of Coimbra Observatory, Portugal

Abstract. The Coimbra Magnetic Observatory (International Association of Geomagnetism and Aeronomy code COI) in Portugal has a long history of observation of the geomagnetic field, spanning almost 150 yr since the first geomagnetic measurements in 1866. These long instrumental geomagnetic records provide very important information about variability of geomagnetic elements and indices, their trends and cycles, and can be used to improve our knowledge on the sources that drive variations of the geomagnetic field: liquid core dynamics (internal) and solar forcing (external). However, during the long life of the Coimbra Observatory, some inevitable changes in station location, instrument's park and electromagnetic environment have taken place. These changes affected the quality of the data collected at COI causing breaks and jumps in the series of geomagnetic field components and local K index. Clearly, these inhomogeneities, typically shift-like (step-like) or trend-like, have to be corrected or, at least, minimized in order for the data to be used in scientific studies or to be submitted to international databases. In this study, the series of local K index and declination of the geomagnetic field are analysed: the former because it allows direct application of standard homogenization methods and the latter because it is the longest continuous series produced at COI. For the homogenization, visual and statistical tests (e.g. standard normal homogeneity test) have been applied directly to the local geomagnetic K index series (from 1951 to 2012). The homogenization of the monthly averages of declination (from 1867 to 2012) has been done using visual analysis and statistical tests applied to the time series of the first differences of declination values, as an approximation to the first time derivative. This allowed not only estimating the level of inhomogeneity of the studied series but also detecting the highly probable homogeneity break points. These points have been cross-checked with the metadata, and the COI series have been compared with reference series from the nearest geomagnetic stations and, in the case of declination series, from the recent geomagnetic field model COV-OBS to set up the required correction factors. As a result, the homogenized series measured in COI are considered to be essentially free of artificial shifts starting from the second half of the 20th century, and ready to be used by the scientific community.

Day-to-Day Variability of H Component of Geomagnetic Field in Central African Sector Provided by Yaoundé-Cameroon Amber Station

The geomagnetic data obtained from Amber Network station in Cameroon have been used for this study. The variability of H component of geomagnetic field has been examined by using geomagnetic field data of X and Y components recorded at AMBER magnetometer station hosted by the Department of Physics of University of Yaoundé (3.87°N, 11.52°E). The day-to-day variability of the horizontal intensity of the geomagnetic field was examined and shows that the scattering of H component of magnetic field variation is more on disturbed than that on quiet condition. The signatures H of geomagnetic Sq and Sd variations in intensities in the geomagnetic element, has been studied. This study shows that the daytime variations in intensities of geomagnetic elements H, Sq(H) and Sd(H) respectively are generally greater than night-time ones. This paper interests answering the two questions: 1) how can geomagnetic variations be used to study the equatorial ionosphere electrodynamics and electrojet equatorial over Africa in general and Cameroon in particular? 2) How can geomagnetic variations be used to monitor and predict space weather events in Cameroon? This paper presents and interprets the results of H component of geomagnetic field variations during magnetic storms and on quiet days.

Magnetospheric and Ionospheric Sources of Geomagnetic Field Variations

This study investigated the magnetospheric and ionospheric sources of geomagnetic field variation using the data set that consists of the hourly values of the geomagnetic element: horizontal intensity H, recorded at the geomagnetic observatory of the Department of physics, university of Ilorin, Ilorin (Long 4.670 and Lat. 8.50, dip 4.1 oS) Nigeria for the months of august, October and December in the year 2008. The study attributed the daytime variation to the ionospheric sources while various reasons were given to explain these night-time variations, which include convective drift currents in the magnetosphere and the asymmetric rings currents in the magnetospheric currents; this variation due to disturbances indicates possible non-ionospheric origin and a partial ring current in the night side magnetosphere. The mean monthly hourly variation showed seasonal variation with the Sq(H) maximizes in equinox with least variation in June solstice. Moreover, the mean ration of seasonal contributions of magnetospheric to ionospheric sources revealed that the E season has more contributions from both magnetospheric and ionospheric sources than other seasons with the least occurring during the J season.

Secular trend of geomagnetic elements in the Indian region

In the present study, secular trends and jerks in the geomagnetic elements D, H and Z are investigated at the six Indian magnetic observatories using annual and monthly mean values for all days, quiet days and night base (night time mean). The residuals of all-day annual and monthly means are computed by removing a polynomial fit from their best fitting curves. The residuals of D, H and Z curves do not show any parallelism with the 11-year sunspot cycle. At Alibag, the D residual shows a periodicity of 2 solar cycles, whereas the H and Z residuals indicate a quasi-periodicity of 3 solar cycles for the period 1921–2009. At the Indian stations, an in-phase solar cycle component is observed for 2 of the solar cycles in the D and Z residuals, while the H residual shows out-of-phase variations with the sunspot cycle for the period 1958–2009. Two geomagnetic jerks, 1970 and 1991, are well reflected in the monthly and annual mean values in the Indian region, as observed globally.

Substitution for lost one-hour means of the geomagnetic elements for the first half of the 20-th century at the Hurbanovo Geomagnetic Observatory by means of neural networks

Abstract The existence of long-acting observatories by itself does not guarantee that their historical magnetograms are available or complete. In the archive of the Hurbanovo Geomagnetic Observatory (acronym HRB; geographical coordinates 47.86 ◦ N, 18.19 ◦ E), records of the geomagnetic field made on photo paper covering the period between the two World Wars were found for which the values of the baselines are unknown. We studied if a feed-forward neural network with one hidden layer can be used to supplement one-hour means of the geomagnetic elements D, H and Z of observatory HRB, using for this purpose the geomagnetic data of observatories Potsdam, Seddin and Niemegk (all of them being referenced to Niemegk). We focused our interest on the first half of the 20-th century. The neural-network model for element D proved to be applicable to substitute for the lost data of the magnetic declination at observatory HRB; however, the usability of the model for both elements H and Z turned out to be limited to a few years close to beginning or end of data gaps. Further we supplemented the time series of annual means of geomagnetic elements D, H and Z at observatory HRB with the model data.

English

This study investigates the possible occurrence of counter equatorial electrojet (CEJ) and a quicker method for identification of CEJ. Data from a chain of magnetic observatories of World Data Center for Geomagnetism in Tokyo, Japan, was employed. It is strikingly interesting to observe that most CEJ occurred from morning through new dusk, with almost the same pattern of dHin depression. In Ascension Island (ASC), Huancayo (HUA) and Pondicherry (PND), most ∆H were found to be less than zero, which reveals an indication of full CEJ. Partial CEJ occurrences were observed during some hours at these stations where ∆Hin >0. It is suggested that IMF turning north indicates CEJ, hence storm effects could also be attributed to CEJ existence. Some of our new findings are at variance with results of some previous workers; hence further work is suggested for further clarification. A quick method of easy identification of CEJ is suggested. Key words: Electrojet, geomagnetic element, counter electrojet, geomagnetism, interplanetary magnetic field (IMF).