Magnetic Observations Research Articles

Conception of Geomagnetic Data Integrated Space

. As is known, today the problem of geomagnetic field and its variations parameters monitoring is solved mainly by a network of magnetic observatories and variational stations, but a significant obstacle in the processing and analysis of the data thus obtained, along with their spatial anisotropy, are omissions or reliable inconsistency with the established format. Heterogeneity and anomalousness of the data excludes (significantly complicates) the possibility of their automatic integration and the application of frequency analysis tools to them. Known solutions for the integration of heterogeneous geomagnetic data are mainly based on the consolidation model and only partially solve the problem. The resulting data sets, as a rule, do not meet the requirements for real-time information systems, may include outliers, and omissions in the time series of geomagnetic data are eliminated by excluding missing or anomalous values from the final sample, which can obviously lead to both to the loss of relevant information, violation of the discretization step, and to heterogeneity of the time series. The paper proposes an approach to creating an integrated space of geomagnetic data based on a combination of consolidation and federalization models, including preliminary processing of the original time series with an optionally available procedure for their recovery and verification, focused on the use of cloud computing technologies and hierarchical format and processing speed of large amounts of data and, as a result, providing users with better and more homogeneous data.

Geomagnetic jerk features produced using synthetic core flow models

Geomagnetic jerks are the shortest temporal variations of the magnetic field generated in the Earth's core. The physical mechanism producing such abrupt changes as well as their spatio-temporal characteristics are not well understood. In order to explore geomagnetic jerks generation and their characteristics, we use a set of synthetic core flow models to solve the radial magnetic induction equation. We analyze changes of trend in the secular variation time series using a cubic polynomial fit, by invoking a new formalism of jerk amplitude per unit duration time. A new visualization scheme allows interpreting jerk amplitudes and occurrences in space and time. We find that a mild time-dependence of flow amplitude, while keeping a fixed pattern, reproduces geomagnetic jerk amplitudes. The polynomial fits were compared with two line-segments fits at ten sampled magnetic observatories about historical jerk occurrences. The differences between the misfits in the two approaches are small, which may question the definition of geomagnetic jerks as sharp “V-shape”. The local time series in our models exhibit secular acceleration changes of sign that reproduce some main observed characteristics of geomagnetic jerks: (i) a range of amplitudes that encompass those observed in geomagnetic jerks, (ii) non-simultaneous occurrence, (iii) non-global occurrence, (iv) spatial variability of amplitudes and (v) strongest amplitudes in the radial component.

Solar quiet variation of the horizontal and vertical components of geomagnetic field using wavelet analysis

The solar quiet (Sq) variations of horizontal and vertical (SqH and SqZ) components of the geomagnetic field obtained from both the Northern Hemisphere and Southern Hemisphere of the International Real-Time Magnetic Observatory Network (INTERMAGNET) during solar maximum year 2001 were investigated. The results show enlargement of the SqH component of the geomagnetic field during the daytime, attributed to equatorial electrojet (EEJ) current closer to the geomagnetic equator at the electrojet stations (BNG and MBO), which are produced from large eastward flow of the current. It was observed that SqZ is positive at the southward and negative at the northward hemispheres. SqZ is amplified at HER and HBK around the daytime. Wavelet power spectrum based approach was employed to analyse the SqH, SqZ, and rate of induction (SqZ/SqH) time series in a sequence of time scaling from January to December. The higher energy of SqH and SqZ of the wavelet coefficients is noticeable at high frequency. The monthly variation rate of induction (SqZ/SqH) analyses during the Sq variations are associated with the influence of equatorwards penetration of electric fields from the field-aligned current, Earth conductivity, effect of the ocean, and ionospheric conductivity.

Статистические взаимосвязи вариаций геомагнитного поля, аврорального электроджета и геоиндуцированных токов

Using observations from the IMAGE magnetic observatories and the station for recording geomagnetically induced currents (GIC) in the electric transmission line in 2015, we examine relationships between geomagnetic field and GIC variations. The GIC intensity is highly correlated (R>0.7) with the field variability |dB/dt| and closely correlated with variations in the time derivatives of X and Y components. Daily variations in the mean geomagnetic field variability |dB/dt| and GIC intensity have a wide night maximum, associated with the electrojet, and a wide morning maximum, presumably caused by intense Pc5–Pi3 geomagnetic pulsations. We have constructed a regression linear model to estimate GIC from the time derivative of the geomagnetic field and AE index. Statistical distributions of the probability density of the AE index, geomagnetic field derivative, and GIC correspond to the log-normal law. The constructed distributions are used to evaluate the probabilities of extreme values of GIC and |dB/dt|.

Statistical relationships between variations of the geomagnetic field, auroral electrojet, and geomagnetically induced currents

Using observations from the IMAGE magnetic observatories and the station for recording geomagnetically induced currents (GIC) in the electric transmission line in 2015, we examine relationships between geomagnetic field and GIC variations. The GIC intensity is highly correlated (R>0.7) with the field variability |dB/dt| and closely correlated with variations in the time derivatives of X and Y components. Daily variations in the mean geomagnetic field variability |dB/dt| and GIC intensity have a wide night maximum, associated with the electrojet, and a wide morning maximum, presumably caused by intense Pc5–Pi3 geomagnetic pulsations. We have constructed a regression linear model to estimate GIC from the time derivative of the geomagnetic field and AE index. Statistical distributions of the probability density of the AE index, geomagnetic field derivative, and GIC correspond to the log-normal law. The constructed distributions are used to evaluate the probabilities of extreme values of GIC and |dB/dt|.

Extreme‐Value Geoelectric Amplitude and Polarization Across the Northeast United States

AbstractMaps are presented of extreme‐value geoelectric field amplitude and horizontal polarization for the Northeast United States. These maps are derived from geoelectric time series calculated for sites across the Northeast by frequency‐domain multiplication (time‐domain convolution) of 172 magnetotelluric impedance tensors, acquired during a survey, with decades‐long, 1‐min resolution time series of geomagnetic variation, acquired at three magnetic observatories. The maps show that, during intense magnetic storms, high geoelectric amplitude hazards are realized across electrically resistive, igneous and metamorphic rock of the Appalachian Mountains and the New England Highlands, while low geoelectric hazards are realized across electrically conductive, sedimentary rock of the Appalachian Plateau and the Mid‐Atlantic Coastal Plain. From statistical extrapolation, once‐per‐century (100‐year) geoelectric amplitudes are highest at a site in Virginia at 25.44 V/km (followed by a site in Maine at 21.75 V/km and a site in Connecticut at 19.39 V/km); 100‐year geoelectric amplitude exceeds 10 V/km at 12 sites across the northeast; geoelectric amplitude is lowest at a site in Virginia at 0.05 V/km. Average errors for these values are estimated to be about 38%, or much less than the more than 2 orders of magnitude range seen in geoelectric amplitudes from one survey site to another across the northeast. It is noteworthy that geoelectric fields tend to be most (least) polarized at locations with high (low) geoelectric hazard. Furthermore, geoelectric fields over the Appalachians tend to be polarized southeast‐to‐northwest, or generally in a direction orthogonal to the southwest‐to‐northeast geological strike. Results reported here inform utility companies in projects for evaluating and managing the response of power grid systems to the deleterious effects of geomagnetic disturbance.

Modeling Geoelectric Fields in Ireland and the UK for Space Weather Applications

AbstractGeoelectric fields at the Earth's surface caused by geomagnetic storms have the potential to disrupt and damage ground‐based infrastructure such as electrical power distribution networks, pipelines, and railways. Here we model geoelectric fields in Ireland and the UK during both quiet and active time intervals of geomagnetic conditions using measurements from magnetic observatories and electromagnetic tensor relationships. The analysis focused on (1) defining periods of the magnetic field variations that are largely affected by the geomagnetic storms, between 30 and 30,000 s; (2) constraining the electromagnetic tensor relationships that defines the Earth's response to magnetic field variations; (3) implementing and validating two approaches for modeling geoelectric fields based on measurements from magnetic observatories and local and interstation electromagnetic transfer functions; and (4) estimating uncertainties when modeling geoelectric fields. The use of interstation tensor relationships allowed us to differentiate between regional and local geomagnetic sources. We found coherence values of 0.5–0.95, signal‐to‐noise ratio of 1–15 dB, normalized root‐mean‐square values of 0.8–3.4, and root‐mean‐square values of 0.7–84 mV/km. Within these ranges of values, sites in close proximity (<100 km) to a magnetic observatory and not affected by local storms will provide the most accurate results, while sites located at further distances and affected by spatially localized features of the storm will be less accurate. These methods enable us to more accurately model geomagnetically induced currents, and their associated uncertainties, in the British and Irish power networks.

Observations from SANSA’s geomagnetic network during the Saint Patrick’s Day storm of 17–18 March 2015

Geomagnetic storms are space weather events that result in a temporary disturbance of the earth’s magnetosphere caused by a solar wind that interacts with the earth’s magnetic field. We examined more closely how some southern African magnetic observatories responded to the Saint Patrick’s Day storm using local K-indices. We show how this network of observatories may be utilised to model induced electric field, which is useful for the monitoring of geomagnetically induced anomalous currents capable of damaging power distribution infrastructure. We show an example of the correlation between a modelled induced electric field and measured geomagnetically induced currents in southern Africa. The data show that there are differences between global and local indices, which vary with the phases of the storm. We show the latitude dependence of geomagnetic activity and demonstrate that the direction of the variation is different for the X and Y components.
 Significance:
 
 The importance of ground-based data in space weather studies is demonstrated.
 We show how SANSA’s geomagnetic network may be utilised to model induced electric field, which is useful for the monitoring of geomagnetically induced anomalous currents capable of damaging power distribution infrastructure.
 
 Open data set: 
 http://www.intermagnet.org/data-donnee/download-eng.php

Time-dependent low-latitude core flow and geomagnetic field acceleration pulses

We present a new model of time-dependent flow at low latitudes in the Earth's core between 2000 and 2018, derived from magnetic field measurements made on board the {\it Swarm} and CHAMP satellites and at ground magnetic observatories. The model, called {\it CoreFlo-LL.1}, consists of a steady background flow without imposed symmetry plus a time-dependent flow that is dominated by geostrophic and quasi-geostrophic components but also allows weak departures from equatorial symmetry. We find that the equatorial region beneath the core-mantle boundary is a place of vigorous, localised, fluid motions; time-dependent flow focused at low latitudes close to the core surface is able to reproduce rapid field variations observed at non-polar latitudes at and above Earth's surface. Magnetic field acceleration pulses are produced by alternating bursts of non-zonal azimuthal flow acceleration in this region. Such acceleration sign changes can occur within a year or less, and when the structures involved are of large spatial scale they can give rise to geomagnetic jerks at the Earth's surface.

Slow variations of the Earth’s magnetic field: technical, methodological and organizational features of measurements

Variations of the Earth’s magnetic field with times of several years or more reflect the processes within the planet and cause great scientific interest. Over the past 100 years the regular observations at magnetic observatories (MOs) and repeat stations are the only experimental basis for studying such variations. In recent decades, satellite measurements have complemented ground-based measurements, thus partially solving the problems of spatially highly heterogeneous global network of magnetic observatories. Absolute observations are made at MOs to get the total field intensity vector. Until now, these measurements are performed manually, they are labor intensity and subject to many factors, that are often poorly controlled and reduce the reliability of the results, especially over long periods of time (years and decades), including (1) systematic errors of used magnetometers; (2) magnetic pollution of the absolute pavilion and its surroundings (at a distance of the first hundred meters); (3) instability of the pillars and remote target required to determine magnetic declination; (4) changes of observers and their weak qualification. Significant methodological problems arise if MO is moved to new location without special activity or infrastructure of MO (pavilions or pillars) is changed without careful control. For long-term stability and reliability of measurements, magnetic observatories were joined in IAGA network and then INTERMAGNET. Within these networks, requirements and standards have been defined, absolute magnetometers are compared every two years and observers are being trained. Modern hardware technologies allow to solve partially problems the automation of absolute observations, the self-calibration of the magnetometers, the checking of the MO’s magnetic environment, etc. Fully automated measurement systems help to expand the MO network.

A Preliminary Risk Assessment of Geomagnetically Induced Currents over the Italian Territory

AbstractGeomagnetically induced currents (GICs), occurring as a result of space weather events, represent a hazard for the secure and safe operation of electrical power grids and oil/gas pipelines. The most exposed countries are those at high latitudes where, in the past, the occurrence of intense GICs has seriously damaged part of their power networks. However, very powerful space weather events have resulted in intense GICs also at middle and low latitudes. The GIC index is a proxy of the geoelectric field, and it can be estimated straightforwardly from magnetic observatory data. In this work, the GIC index is computed to investigate the possible impact of space weather events on the Italian territory. We first calculate the GIC index using data from the magnetic observatories of Castello Tesino, Duronia, and Lampedusa, together covering the whole Italian latitudinal extension, and show its behavior during the 2015 St. Patrick's day storm. Then, we consider measurements from the two longest running Italian magnetic observatories, that is, Castello Tesino and L'Aquila, and estimate the GIC index over more than 20 years of observations. A preliminary characterization of the general risk to which the Italian power grid network is exposed is given. Results show that during periods of high magnetic activity, potentially detrimental GICs could flow through the power network, especially at the highest Italian latitudes that are characterized by a low conductivity lithosphere.

Characterization of Cameras for the COSMO K-coronagraph

Abstract Digital image sensors are ubiquitous in astronomical instrumentation and it is well known that they suffer from issues that must be corrected for data to be scientifically useful. I present discussion on errors resulting from digitization and characterization of nonlinearity and ADC errors of the PhotonFocus MV-D1024E cameras selected for the K-coronagraph of the Coronal Solar Magnetism Observatory. I derive an analytic expression for quantization errors. The MV-D1024E camera has adequate bit depth for which quantization error is not an issue. I show that this is not the case for all cameras, particularly those with deep wells and low read noise. The impact of nonlinearity and ADC errors on science observations of the K-coronagraph is analyzed using a simplified telescope model. Errors caused by the camera ADCs result in systematic errors in the measurement of the polarimetric signal of several times 10−9 B ⊙, which is about an order of magnitude above the desired sensitivity. I demonstrate a method for post-facto data correction using a lookup table and derive parameters from camera characterization measurements that were made with a lab setup. Nonlinearity is traditionally addressed with a global correction. I show through analysis of calibration data that for the MV-D1024E this correction leaves residual systematic errors after dark and gain correction of up to 1% of the signal. I demonstrate that a pixel-wise correction of nonlinearity reduces the errors to below 0.1%. These corrections are necessary for the K-coronagraph data products to meet the science requirements. They have been implemented in the instrument data acquisition system and data reduction pipeline. While no other instruments besides the K-coronagraph or cameras besides the MV-D1024E are discussed here, the results are illustrative for all instruments and cameras.

Ensino de Geociências na universidade

RESUMO No Brasil colonial, apesar de intensa atividade mineira na busca de ouro e diamantes, não houve práticas geocientíficas relevantes. No século XIX ocorreram diversas explorações geológicas, das quais resultou uma vasta contribuição escrita. Além disso foram criadas importantes instituições, como o Observatório Nacional, o Serviço Meteorológico, o Observatório Magnético de Vassouras e a Escola de Minas de Ouro Preto em 1876. O ensino formal de Geociências no Brasil foi iniciado apenas em 1957, com a Campanha de Formação de Geólogos (CAGE), que criou e forneceu recursos materiais e humanos para quatro cursos de graduação em Geologia. Na Meteorologia a graduação se iniciou em 1963, na Oceanografia em 1971, e na Geofísica em 1983. Atualmente, 47 universidades brasileiras oferecem 71 cursos de graduação nas Geociências. Há 33 cursos de Geologia, três de Engenharia Geológica, 14 de Meteorologia, 13 de Oceanografia e 8 de Geofísica. Há no Brasil 57 programas de pós-graduação em Geociências, 13 dos quais considerados de excelência, indicando que a situação atual da área é de consolidação e maturidade. Geólogos e geofísicos foram absorvidos, em sua maioria, pelas atividades de mapeamento geológico, exploração mineral e de petróleo. Meteorologistas dedicaram-se ao monitoramento meteorológico e climático, e também a projetos de energia hidroelétrica, eólica e solar. Na Oceanografia, os formados atuaram em órgãos relacionados com ambiente, agricultura e no Ministério da Marinha. Quanto à pesquisa, as ciências atmosféricas e oceanográficas são de grande relevância global, no estudo das mudanças climáticas e o aquecimento global. Por sua vez, o maior desafio de geólogos e geofísicos é o de melhorar do conhecimento do território brasileiro, na escala local ou regional.

Historical Database of Geomagnetic and Auroral Activity for the Study of Solar–Terrestrial Relationships

In situ data on geomagnetic and auroral activity obtained in recent years has contributed to a greater understanding of solar–terrestrial processes. However, because space exploration began only in the middle of the 20th century, in situ data are insufficient to analyze geomagnetic variations and solar-activity variations on a time scale from decades to centuries. The Russian network of magnetic and meteorological observatories provides one of the longest data series. For example, the magnetograms from St. Petersburg (SPE), Pavlovsk (SLU), and Voeikovo (LNN) stations provide long series of continuous records of variations of declination (D) and horizontal (H) and vertical (Z) components of the geomagnetic field. The aim of this paper is to make this data publicly available. For this purpose, a specialized database has been developed for the study of various aspects of solar–terrestrial relationships, including heliobiomagnetology. The database contains (1) digital images of analog magnetograms from SPE (1869–1877) and SLU (1878–1921, images for 1921–1941 are still being scanned), (2) hourly values of declination D and horizontal H and vertical Z components of the geomagnetic field obtained at SPE and SLU stations for 1869–1914, (3) data on geomagnetic storms from the SLU station for 1878–1941 and from the LNN station for 1947–1954, and (4) data on aurora borealis observed at 141 stations of the Russian Meteorological Network for 1837–1909. The database is designed to provide online access to the Russian collection of historical data on geomagnetic and auroral activity. On this basis, it is possible to carry out research on various aspects of space weather and climate and use it, among other things, to solve problems of heliomagnetobiology. Users are provided with easy access to individual magnetograms at different zoom levels. Online access will allow a wide range of researchers to use these databases to solve problems related to historical space weather data.

The Eruption of a Prominence-carrying Coronal Flux Rope: Forward Synthesis of the Magnetic Field Strength Measurement by the COronal Solar Magnetism Observatory Large Coronagraph

From a magnetohydrodynamic (MHD) simulation of the eruption of a prominence hosting coronal flux rope, we carry out forward synthesis of the circular polarization signal (Stokes V signal) of the FeXIII emission line at 1074.7 nm produced by the MHD model as measured by the proposed COronal Solar Magnetism Observatory (COSMO) Large Coronagraph (LC) and infer the line-of-sight magnetic field BLOS above the limb. With an aperture of 150 cm, integration time of 12 min, and a resolution of 12 arcsec, the LC can measure a significant BLOS with sufficient signal to noise level, from the simulated flux rope viewed nearly along its axis with a peak axial field strength of about 10 G. The measured BLOS is found to relate well with the axial field strength of the flux rope for the height range of the prominence, and can discern the increase with height of the magnetic field strength in that height range that is a definitive signature of the concave upturning dipped field supporting the prominence. The measurement can also detect an outward moving BLOS due to the slow rise of the flux rope as it develops the kink instability, during the phase when its rise speed is still below about 41 km/s and up to a height of about 1.3 solar radii. These results suggest that the COSMO LC has great potential in providing quantitative information about the magnetic field structure of CME precursors (e.g. the prominence cavities) and their early evolution for the onset of eruption.

RESPONSE OF BIOLOGICAL SYSTEMS TO GEOMAGNETIC STORMS

At present, influence of weak magnetic fields associated with solar and geomagnetic activity on biological systems is gaining more interest. Taking into account the accumulated data on the influence of geomagnetic storms on different biological levels, it is obvious that the mechanism of influence is universal. One of the approaches in this search may be the study of patterns and differences in the response to geomagnetic storms of various biological objects. As a research material served: data on the number of ambulance calls in the city of Irkutsk for acute myocardial infarction, cerebral infarction; results of retrospective analysis of the number of spontaneous parturition of the city of Irkutsk; data on the motion activity of fruit fly Drosophyla melanogaster, obtained by automated monitoring. The investigated indicators were compared with the parameters of geomagnetic activity at different time scales. As indicators of geomagnetic storms, three-hour (ap) and daily (Ap) equal to the average amplitude of variation of the geomagnetic field of the Earth. In the case of comparing the motion activity of fruit flies with magnetic storms, the local companions of the Earth’s magnetic field were additionally considered according to the data of the Irkutsk magnetic observatory. As a result of the conducted studies it was established that the detected response of biological systems depends on the characteristics of the state of the Earth’s magnetic field, which falls on the period of passage of magnetic storms. The obtained data also indicate possible gender differences in the response to the effects of the geomagnetic factor by organisms of different levels.

Latitudinal dependence of geomagnetically induced currents during geomagnetic storms

Major geomagnetic storms drive rapid intensification and variability of magnetospheric and iono- spheric current systems that give rise to large ground-induced currents (GIC). Space weather as- sociated GIC pose a serious threat to the reliability of power-transmission systems and other elec- trically conducting infrastructure such as oil and gas pipelines. The most severe effects are ob- served at high latitudes due to ionospheric currents associated with the aurora. However, as power transmission grid and pipeline infrastructure continues to grow at middle and low-latitudes, GIC hazards are no longer just concerns of high-latitude regions. We investigate how GIC amplitude varies in latitude during six major geomagnetic storms that occurred between 1989 and 2004. Due to limited direct GIC measurements, a proxy of the geoelectric field is used, i.e. the GIC index. This is calculated for the selected geomagnetic storms using 25 magnetic observatories relatively uniformly distributed in geomagnetic latitude, 14 magnetic observatories with longitudes varying within a range of 45 degrees as well as for the 7 November 2004 storm using 104 observatories. In addition, we suggest a possible way to follow the latitudinal displacement of the auroral oval dur- ing geomagnetic storms through the maximum value of GIC index, estimated over 2-hour inter- vals on a wide number of magnetic observatories.

Multiscale variation model and activity level estimation algorithm of the Earth's magnetic field based on wavelet packets

Abstract. We suggest a wavelet-based multiscale mathematical model of geomagnetic field variations. The model is particularly capable of reflecting the characteristic variation and local perturbations in the geomagnetic field during the periods of increased geomagnetic activity. Based on the model, we have designed numerical algorithms to identify the characteristic variation component as well as other components that represent different geomagnetic field activity. The substantial advantage of the designed algorithms is their fully automatic performance without any manual control. The algorithms are also suited for estimating and monitoring the activity level of the geomagnetic field at different magnetic observatories without any specific adjustment to their particular locations. The suggested approach has high temporal resolution reaching 1 min. This allows us to study the dynamics and spatiotemporal distribution of geomagnetic perturbations using data from ground-based observatories. Moreover, the suggested approach is particularly capable of discovering weak perturbations in the geomagnetic field, likely linked to the nonstationary impact of the solar wind plasma on the magnetosphere. The algorithms have been validated using the experimental data collected at the IKIR FEB RAS observatory network. Keywords. Magnetospheric physics (storms and substorms)

Approach to Assessment of the Relative Informational Efficiency of Intermagnet Magnetic Observatories

The IAGA-2002 1-min geomagnetic time series published by the International Real-time Magnetic Observatory Network (INTERMAGNET) are considered. Their completeness and anomalies are analyzed. The concept of the relative informational efficiency index is introduced. Theory elements are developed for its qualitative and quantitative assessment. Time series of geomagnetic data published by INTERMAGNET for 2014–2017 are used to find the range for the determination of this index and its basic statistical characteristics. An approach to the classification of INTERMAGNET magnetic observatories by the relative informational efficiency index is proposed. The nature of the geospatial distribution of the appropriate classes of magnetic observatories is investigated.

Hermanus Magnetic Observatory: a historical perspective of geomagnetism in southern Africa

Abstract. 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.