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1

Possible risk resulting from the recent decay of the dipolar component of the terrestrial magnetic feld

Bury Agata, Lewandowski Marek, Mizerski Krzysztof

Acta Geophysica

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2021

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Vol. 69, no. 1

47--52

EN

In this study, we investigated the geomagnetic ground observatory data from 1980 to 2011 collected from World Data Center from 134 stations. To analyze the data we have applied spherical harmonic decomposition to obtain components associated with the Earth’s main magnetic feld and to calculate how the Earth’s dipole was varying in the aforementioned recent 31-year period. There is a visible ~2.3% decay of the dipole magnetic feld of the Earth. We note that the present-day value of the magnetic dipole intensity is the lowest one in the history of modern civilization and that further drop of this value may pose a risk for diferent domains of our life.

2

Assessment of signal processing methods for geomagnetic precursor of the 2012 M6.9 Visayas, Philippines earthquake

Yusof Khairul Adib, Hamid Nurul Shazana Abdul, Abdullah Mardina, Ahadi Suaidi, Yoshikawa Akimasa

Acta Geophysica

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2019

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Vol. 67, no. 5

1297--1306

EN

This study assessed two signal processing methods on geomagnetic data to detect precursory signals appearing before the M6.9 Visayas, Philippines earthquake on 6 February 2012. It aimed to compare the polarization ratio analysis method with the diurnal variation ratio method in terms of reliability and efectiveness. The geomagnetic data were obtained from the MAGDAS magnetometer network for Cebu (CEB) and Legazpi (LGZ) stations which served as the primary and remote stations, respectively. The polarization ratio analysis method was performed on the primary station data to obtain power spectral density in an ultra-low-frequency range before fnding the ratio of vertical to total horizontal component. Meanwhile, the diurnal variation ratio method was used to calculate the diference between the daily maximum and minimum values. Then, the ratio of the daily diferences of the primary station to the remote station for each individual component was calculated. The disturbance storm time index which describes global geomagnetic activity originating from the Sun was utilized to verify that any observed geomagnetic fuctuations were not caused by solar-terrestrial efect. A precursory anomaly was found using the polarization ratio analysis method which appeared 2 weeks before the earthquake. It is concluded that this method might be efective and reliable in detecting geomagnetic anomalies preceding upcoming earthquakes. In contrast, although the diurnal variation ratio method did show perceivable fuctuations, the running averages were not statistically significant to be considered a precursor. The discrepancy between the analytical results of the two methods may be attributed to the detectability of the earthquake being studied which had a relatively low magnitude. Hence, future studies which utilize more earthquake events need to be conducted to reach a definitive conclusion.

3

Geoelektromagnetyzm skał

Gierlotka S.

Wiadomości Elektrotechniczne

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2018

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R. 86, nr 8

17--20

4

Spherical Elementary Current Systems Method Applied to Geomagnetic Field Modeling for the Adriatic

Vujić E., Brkić M.

Acta Geophysica

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2016

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Vol. 64, no. 4

930--942

EN

The aim of this work was to derive an accurate regional model of geomagnetic components on the Adriatic. Data of north, east and vertical geomagnetic components at repeat stations and ground survey sites enclosing the Adriatic Sea were used to obtain a geomagnetic model at 2010.5 epoch. The core field was estimated by use of the global Enhanced Magnetic Model, while the crustal field by a mathematical technique for expanding vector systems on a sphere into basis functions, known as spherical elementary current systems method. The results of this method were presented and compared to the crustal field estimations by the Enhanced Magnetic Model. The maps of isolines of the regional model are also presented.

5

Regional Geomagnetic Field Model for Croatia at 2009.5

Vujcić E., Brkić M., Kovács P.

Acta Geophysica

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2016

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Vol. 64, no. 1

26--42

EN

Geomagnetic data of north, east, and vertical components at Croatian repeat stations and ground survey sites, as well as European geomagnetic observatories and repeat stations, were used to obtain a regional geomagnetic model over Croatia at 2009.5 epoch. Different models were derived, depending on input data, and three modelling techniques were used: Taylor Polynomial, Adjusted Spherical Harmonic Analysis, and Spherical Harmonic Analysis. It was derived that the most accurate model over Croatia was the one when only Croatian data were used, and by using the Adjusted Spherical Harmonic Analysis. Based on Croatian repeat stations’ data in the interval 2007.5-2010.5, and a global Enhanced Magnetic Model, it was possible to estimate the crustal field at those sites. It was also done by taking into account the empirical adjustment for long-term external field variations. The higher crustal field values were found at those stations which are on or close to the Adriatic anomaly.

6

Model dipolowy

Sas-Uhrynowski A., Welker E.

Geodeta : magazyn geoinformacyjny

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2006

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nr 1

24-27

7

Installation for compensating negative impact of geomagnetic storms onto human organism

Khomeriki O., Kachukhashvili G., Gheonjian L., Invia N.

Biocybernetics and Biomedical Engineering

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2004

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Vol. 24, no. 1

49-60

EN

It is known that during the geomagnetic storms an increase of the functional activity of the cardiovascular dosorders. Previous attempts to protect patients from geomagnetic storms by the use of iron shielding seem not have been quite successful. An alternative possibility is to use active shielding, or rather a compensatory method, which involves the creation in a hospital room of three-dimensional magnetic field time-varying within the normal variations of the geomagnetic field. The generated field must be maximally uniform, it must compensate for magnetic disturbances while retaining natural geomagnetic conditions - the main (quasi-constant) geomagnetic field as well as its short-periodic variations. To satisfy these requirements theoretical calculations and their experimental examinations have been carried out. Investigations using a magneto-compensating installation should give an answer to the fundamental question: are the variations of the geomagnetic field, as one of the consequences of the solar activity, the major, or at least a sufficient factor responsible for exacerbation of disorders of cardiovascular system? If the answer is affirmative, the installation could be recommended for use clinical practice.

8

Badania zmian wiekowych pola geomagnetycznego na terytorium Polski i Białorusi

Sas-Uhrynowski A., Karatajew H., Mroczek S., Karagodina O.

Prace Instytutu Geodezji i Kartografii

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2000

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T. 47, z. 100

25--34

PL

Praca zawiera opis sieci magnetycznych punktów wiekowych założonej przez polsko-białoruski zespół specjalistów. Sieć liczy 11 punktów. Na 7 z nich zostały już wykonane pierwsze pomiary deklinacji i inklinacji magnetycznej oraz pomiary modułu wektora indukcji magnetycznej. Ponadto Obserwatorium Magnetyczne Pleszczenice zostało dowiązane do obserwatoriów europejskich w wyniku przeprowadzenia odpowiednich pomiarów porównawczych.

EN

In 1997, eleven magnetic secular variation (SV) stations on the Belarussian territory were established. These stations, together with the Magnetic Observatory Pleshchenice, create the Belarussian SV network. In 1996, the Magnetic Observatory Pleshchenice was connected with European observatories Belsk (Poland) and Niemegk (Germany) by means of comparison measurements, performed using proton magnetometer and magnetometer Flux D/I.. In summer 1997, at seven SV stations the first set of 3 day observations were made using the same magnetometers. The rest (4) stations in 1998 will be observed. Both, Belarussian SV network and the Polish one which consists of 19 stations and 2 observatories - Belsk and Hel, will be used for research o f the magnetic secular variations on the territories of both countries. The main attention will be paid on the Northern-part o f the Prccambrian Platform. It is planed also to include the Lithuanian SV network into common research.

9

On vector representation of secular variation of the geomagnetic field

Demina I.M., Kasyanenko L.G., Uhrynowski A.

Prace Instytutu Geodezji i Kartografii

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1998

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T. 45, z. 96

73--107

EN

In the paper, there is presented a comparison analysis of resultant secular changes of moduli [delta]F and [delta]H increments, and the resultant changes of vector moduli ׀[delta]F׀ and ׀[delta]H׀. It has been pointed out that in some cases the character of the secular geomagnetic changes is improperly represented by charts of isopors.

PL

W pracy przedstawiono globalne mapy zmian indukcji pola geomagnetycznego w wektorowej postaci, zestawione dla dziesięcioletnich interwałów, począwszy od 1920 r. Wskazano na istnienie rozbieżności pomiędzy zmianami przyrostów modułów [delta]F i [delta]H a wypadkowymi zmian modułu wektora ׀[delta]F׀ i ׀[delta]H׀. Wykazano, że mapy reprezentujące charakter zmian pola, w pewnych wypadkach są jakościowo niewłaściwe. Taki sam wniosek można także wysnuć w odniesieniu do map niedipolowej części pola dla składowej Z na Południowej Półkuli. W szczególności należy podkreślić, że wykorzystanie wypadkowych zmian wiekowych pola geomagnetycznego, zamiast rocznych, jest bardziej słuszne dla rozwiązywania pewnych, ostatnio dyskutowanych zagadnień na przykład anomalii pośrednich.