Geomagnetic observatory

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A geomagnetic observatory , also called geomagnetic observatory , is a device for the continuous observation, recording and documentation of the temporal and local fluctuations of the earth's magnetic field by means of various measuring instruments.

The location of a geomagnetic observatory should be free of local geological features. Electric railways should be more than 15 km, water and sewage systems more than 200 m from the measuring station. High-voltage lines should also not be located in the vicinity of the observatory, as these can cause disturbances in the measurements depending on the operating load and the direction of the location. The structures of the observatory should be made of non-magnetic materials. In general, conductive materials should be avoided, as the magnetic sensors could be influenced by the eddy currents caused by seismic vibrations in the metal . A stable platform is also required for most of the measuring instruments to be installed.

Adolf Schmidt Observatory in Niemegk, Absoluthaus inside

tasks

The long-term variations of the three components declination , inclination and total intensity are recorded with different magnetometers in order to determine the secular variation of the earth's magnetic field. The daily variations as well as the seasonal fluctuations of the geomagnetic field and its relationship to solar activity are also analyzed and published as the degree of disturbance of the geomagnetic field in the form of indicators. These data are u. a. sent as minute averages to the world data centers and published as annual averages in the yearbooks of the observatories. Thus they are available for worldwide research. There is now a global network of around 200 observatories that participate in the data exchange.

The measurement data obtained are not only used for scientific research into the earth's magnetic field, but also have practical uses. Declination maps were used earlier and sometimes still today for navigation in shipping and aviation. For the search for raw materials such as B. ore and oil deposits, the geomagnetic measurement data are important. They are also used in biological and medical research. The activity indicators of the earth's magnetic field are u. a. useful for wireless communication: high numbers mean e.g. For example, that the quality of satellite positioning via GPS drops and communication via shortwave is severely disrupted.

history

Alexander von Humboldt carried out systematic measurements in Prussian mining and on his research trips. In 1829 the Imperial Academy in St. Petersburg followed his proposals and set up several stations in Russia.

Carl Friedrich Gauß built the first geophysical observatory in Göttingen and constructed a sensitive magnetometer for it in 1832 . He recognized that globally distributed measurements would have to take place at the same time in order to localize the causes of the fluctuations and to be able to measure the static field more precisely. The Magnetischer Verein, founded for this purpose, and the British Royal Society supplied data from 1836, which he and Wilhelm Weber evaluated. In 1839 he was able to show that the main part of the earth's static magnetic field comes from inside the earth, while smaller, short-term variations of the earth's magnetic field come from outside. Since Weber lost his professorship as a scientist who belonged to the "Göttinger Sieben", who had signed a protest note against the king's breach of the constitution, the measurements were continued in Leipzig in 1848, where an independent control room was set up in a separate building.

Further international measurement campaigns took place during the polar years of 1882, 1932 and in the International Geophysical Year 1957–1958. The earlier mechanical magnetometers ( magnetic field balances , torsion magnetometers ) were increasingly being replaced by inductive or atomic (saturation core, fluxgate ( Förster probes ); proton and cesium) magnetometers.

In terms of industrial history, the development of corresponding precision measuring devices in Germany in cooperation with research was closely connected with the Askania works in Potsdam, for example with Schmidt's field scales, which are widespread around the world and , in addition to measuring regional data of the earth's magnetic field, also allowed the estimation of the magnetization of rock samples.

The spatial distribution of the earth's magnetic field between the geomagnetic observatories was initially provided by shipping. This task is increasingly taken over by specialized satellites, Magsat 1980, the Danish satellite Oerstedt 1999, the four cluster satellites 2000, CHAMP 2000, SWARM 2013. Spatial coverage of relatively slow fluctuations has been good since then, while the currently more than 200 laboratories for coordinated monitoring are shorter Variations are indispensable.

The mining authorities in Ibbenbüren and Bochum initially carried out measurements with simple compasses from 1844 onwards. In 1854, the first iron-free house was built in order to take regular measurements with measuring instruments such as the Breitkamp Declinatoria.

The Westfälische Berggewerkschaftskasse (WBK) set up its first magnetic control room in Bochum in 1888, but this had to be relocated several times due to the industrialization of the area with its iron masses and stray currents from the overhead lines of the trams. In 1912 she moved her waiting south of the Ruhr to a sparsely populated mountain ridge in Vossnacken . The control room was closed in 1946, as the increasing steel expansion of the coal pits made magnetic measurements almost impossible.

Geomagnetic observatories in Germany

There are four geomagnetic observatories in Germany:

  • the geomagnetic observatory in Wingst .

Historical observatories:

  • Bochum , control room of the mining office, founded in the 1840s, housed in an independent building by the Westfälische Berggewerkschaftskasse (WBK) in 1888 and moved to Vossnacken in 1912 .
  • Ibbenbüren , control room of the mining authority, founded in the 1840s.
  • Leipzig , founded in 1848 by Wilhelm Eduard Weber, moved several times on the university grounds, building was demolished in the 1970s.
  • Wilhelmshaven , the marine observatory, had carried out geomagnetic observations for several decades since 1878, the devices were handed over to the Wingst control room in 1936.
  • Geomagnetic Observatory Wingst , control room of the Deutsche Seewarte , founded in 1938, last operated by GFZ Deutsches GeoForschungsZentrum until 2019.
  • Vossnacken , built in the garden of the Vossnacker School in 1912 and looked after by the main teacher, discontinued in 1948.

literature

  • Glückauf, Berg - und Hüttenmänische Zeitschrift, No. 51, December 21, 1912, Volume 48, page 2061 to page 2070 "The new self-writing declinatorium for the Lower Rhine-Westphalian coal district."
  • Wallace H. Campbell: Introduction to geomagnetic fields , Cambridge University Press, 1997, ISBN 0-521-57193-6

Individual evidence

  1. ↑ Researchers discover forgotten history in Langenberg at: derwesten.de from November 3, 2015
  2. ^ Geomagnetic Observatories. Retrieved July 18, 2020 .
  3. ^ Schulz, G .: 60 Years of the Earth Magnetic Observatory Wingst, From the Deutsche Seewarte Hamburg to the GeoforschungsZentrum Potsdam, 2001.
  4. ↑ GFZ Potsdam - Observatories operated by the GFZ.
  5. ↑ Welt.de: Buyer wanted for observatory and ex-manor Heisenhof
  6. ↑ see also 75 years of the Earth Magnetic Observatory Wingst - a review, in: DGG-Mitteilungen 2013

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