The Repeat Station Network and Estimation of Secular Variation in the Australian Region

Abstract:The second part of the history of the Algerian magnetic repeat station network goes back to 1989 when the new one was started with 37 stations. It was then followed by three other networks in 1993, 1997 and 2005. The first part of this history started at the beginning of the XXth and ended ca 1956.After a 14-year break, we launched a new repeat stations network in February 2019. The number of carried out stations was increased to 51 to try to cover all the territory.Each repeat station network consists of stations of periodically, say &#160;5-6 years, measured of three components of the Earth's magnetic field. to try to derive the spatial distribution of the geomagnetic field of Algeria and it's secular variation. This periodicity is also very important for the need to update local as well as global geomagnetic field models such as the International Geomagnetic Reference Field (IGRF).In this work we describe the new 2019 Algerian repeat station network. Then we will discuss the steps of the absolute measurements using two methods. The first one is called the &#8216;method of zero&#8217; and the second one &#8216;method of residuals&#8217;. The accuracy and resolution of the instruments and data reduction used and their effect on the final results will as well be discussed. We derive the spatial distribution of the geomagnetic field, and its secular variation. Finally, we will show how local, for instance regional polynomial modeling, is the key issue.Key words: geomagnetic repeat network, absolute measurements, zero method, residual method, magnetic maps of Algeria, secular variation.

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Secular variation on the territory of the Czech Republic and reduction of the magnetic survey to the epoch 2010.5

Annals of Geophysics ◽

10.4401/ag-5445 ◽

2013 ◽

Vol 55 (6) ◽

Author(s):

Pavel Hejda ◽

Josef Horáček ◽

Tomáš Bayer

Keyword(s):

Czech Republic ◽

Secular Variation ◽

Magnetic Survey ◽

The Czech Republic ◽

Station Network ◽

First Order ◽

Repeat Station ◽

Basic Network ◽

Three Components

A recent stage of the magnetic surveying activities in the Czech Republic was started in the fifties by setting up a basic network of the first order. It consists of 199 points. Complete measurements of three components, D, H, and Z, were carried out in 1976-78 and 1994-96. Since 1970 six selected points have been revisited approximately every two years. Five of them are situated close to the Czech boundaries, the last one inland. The repeat station network was complemented by another inland station in 2003. The repeat station measurements, together with the data from neighboring observatories, were now used to reduce the data from the last magnetic survey to the epoch 2010.5 and new magnetic charts were drawn. The accuracy of the results and their comparison with IGRF model is also discussed.

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Repeat station data compared to a global geomagnetic field model

Annals of Geophysics ◽

10.4401/ag-5410 ◽

2013 ◽

Vol 55 (6) ◽

Author(s):

Monika Korte ◽

Vincent Lesur

Keyword(s):

Magnetic Field ◽

Secular Variation ◽

Global Model ◽

Time Interval ◽

Night Time ◽

Core Field ◽

Repeat Station ◽

Station Data ◽

Long Term Trends

Geomagnetic repeat station surveys with local variometers for improved data reductions have been carried out in Germany for about ten years. For nearly the same time interval the satellites Ørsted and CHAMP have provided a good magnetic field data coverage of the whole globe. Recent global field models based on these satellite data together with geomagnetic observatory data provide an improved description of the core field and secular variation. We use the latest version of the GFZ Reference Internal Magnetic Model to compare the magnetic field evolution predicted by that model between 2001 and 2010 to the independent repeat station data collected over the same time interval in Germany. Estimates of crustal bias at the repeat station locations are obtained as averages of the residuals, and the scatter or trend around each average provides information about influences in the data from field sources not (fully) described by the global model. We find that external magnetic field signal in the order of several nT, including long-term trends, remains both in processed annual mean and quiet night time repeat station data. We conclude that the geomagnetic core field secular variation in this area is described to high accuracy (better than 1 nT/yr) by the global model. Weak long-term trends in the residuals between repeat station data and the model might indicate induced lithospheric anomalies, but more data are necessary for a robust analysis of such signals characterized by very unfavorable signal-to-noise ratio.

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New Slovak geomagnetic repeat station network

Earth Planets and Space ◽

10.1186/bf03351978 ◽

2006 ◽

Vol 58 (6) ◽

pp. 751-755

Author(s):

Fridrich Valach ◽

Magdalena Vaczyova ◽

Peter Dolinsky

Keyword(s):

Station Network ◽

Repeat Station

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Improved observations at the southern African geomagnetic repeat station network

South African Journal of Geology ◽

10.2113/gssajg.110.2-3.175 ◽

2007 ◽

Vol 110 (2-3) ◽

pp. 175-186 ◽

Cited By ~ 13

Author(s):

M. Korte ◽

M. Mandea ◽

P. Kotze ◽

E. Nahayo ◽

B. Pretorius

Keyword(s):

Station Network ◽

Repeat Station

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MAGNETIC REPEAT STATION NETWORK IN ITALY AND MAGNETIC MEASUREMENTS AT HELIPORTS AND AIRPORTS

Geomagnetics for Aeronautical Safety ◽

10.1007/978-1-4020-5025-1_20 ◽

2007 ◽

pp. 259-270 ◽

Cited By ~ 1

Author(s):

ANGELO DE SANTIS ◽

GUIDO DOMINICI

Keyword(s):

Magnetic Measurements ◽

Station Network ◽

Repeat Station

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Repeat-station surveys: implications from chaos and ergodicity of the recent geomagnetic field

Annals of Geophysics ◽

10.4401/ag-5491 ◽

2013 ◽

Vol 56 (1) ◽

Author(s):

Angelo De Santis ◽

Enkelejda Qamili ◽

Gianfranco Cianchini

Keyword(s):

Time Series ◽

Phase Space ◽

Time Domain ◽

Secular Variation ◽

Geomagnetic Field ◽

Repeat Station ◽

Reconstructed Phase Space ◽

Time Averages ◽

The Time Domain ◽

Strong Necessity

The present geomagnetic field is chaotic and ergodic: chaotic because it can no longer be predicted beyond around 6 years; and ergodic in the sense that time averages correspond to phase-space averages. These properties have already been deduced from complex analyses of observatory time series in a reconstructed phase space and from global predicted and definitive models of differences in the time domain. These results imply that there is a strong necessity to make repeat-station magnetic surveys more frequently than every 5 years. This, in turn, will also improve the geomagnetic field secular variation models. This report provides practical examples and case studies.

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Ukrainian geomagnetic repeat station network and results of the field work reduced to the epoch 2005.5

Annals of Geophysics ◽

10.4401/ag-5406 ◽

2013 ◽

Vol 55 (6) ◽

Author(s):

Valentyn Maksymchuk ◽

Myxailo Orlyuk ◽

Viktor Tregybenko ◽

Yurij Horodyskyy ◽

Dmytro Marchenko

Keyword(s):

Geomagnetic Field ◽

Field Work ◽

Station Network ◽

Repeat Station ◽

Geodetic Measurements ◽

Magnetic Declination

The results of geomagnetic field components of the renewed Ukrainian repeat stations (RS) network are presented. The methods of absolute geomagnetic and astro-geodetic measurements are described. The reduction of geomagnetic field components is carried out to the 2005.5 epoch and a catalogue of RS is created. Maps of magnetic declination for the Ukraine are constructed and compared with results calculated by the IGRF-2005 model.

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The 1990.0 magnetic repeat station survey and normal reference fields for Italy

Annals of Geophysics ◽

10.4401/ag-4185 ◽

1994 ◽

Vol 37 (5) ◽

Author(s):

A. Meloni ◽

O. Battelli ◽

A. De Santis ◽

G. Dominici

Keyword(s):

Secular Variation ◽

Data Reduction ◽

Measuring Equipment ◽

Field Data ◽

Data Mapping ◽

Reduction Procedure ◽

Normal Field ◽

Repeat Station ◽

Magnetic Network ◽

Reference Fields

A survey of 116 repeat stations of the Italian Magnetic Network was carried out between 1989 and 1992. We describe the characteristics of the selected network repeat station sites, the characteristics of the measuring equipment, the data reduction procedure and the analysis in terms of normal field, data mapping and secular variation. Together with the values from our previous campaigns, we also determined, for all elements, the normal fields of secular variation. The new repeat station data are listed. Results, maps and normal fields are discussed with respect to previous work and future survey plans.

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