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Research | Space Research | Geomagnetic field - Nurmijärvi Geophysical Observatory
Nurmijärvi Geophysical Observatory
The slow secular change of the Earth's magnetic field is detected at about 200 geomagnetic observatories all around the world. In Finland, there are two permanent observatories: Nurmijärvi and Sodankylä. The Nurmijärvi Geophysical Observatory was founded in the beginning of 1950's on shore lake Sääksjärvi, far away from man-made magnetic disturbances, about 40 km north-west from Helsinki.
The magnetic field is recorded in a separate building with two fluxgate magnetometers. Samplings are taken every second of all three components of the field, and results are delivered to the international scientific community. To control the secular change, magnetometer readings are checked weekly by an absolute measurement. It is performed in another building by using a non-magnetic theodolite (to detect the direction of the field), a fluxgate instrument and a proton magnetometer (to measure the total amplitude).
The absolute measurement equipment is also used at special measurement points in Finland to record the secular change in a regional scale. The measurement is performed about once a year at each site. During recent years, similar measurements have been performed in Estonia to derive magnetic charts for the country.
The Nurmijärvi observatory is an active partner in the IMAGE magnetometer network project. The observatory staff is responsible to operate and maintain eight IMAGE stations. Recordings are daily transfered via telephone lines to the observatory where data are carefully checked before international delivery.
A speciality of the observatory is its magnetic test laboratory where it is possible to calibrate magnetic instruments, or measure magnetic properties of any (small) bodies, e.g. of instruments installed in space research satellites. There is a separate building for the laboratory including a large coil system with which a desired magnetic field can be created. The fast and accurate system has been developed in co-operation with the Ukrainian Lviv Centre of Space Research Institute. A copy of the calibration equipment was delivered to Geosciense Australia (AGSO Canberra, Australia) in 1999.
There are also other recording systems in the area of the observatory. Magnetic pulsations are measured with magnetometers by the Oulu and York Universities. Seismological Institute of the Helsinki University has one of its seismic recording stations in the area. An automatic MILOS weather station is operated by the Finnish Meteorological Institute, as well as an equipment for monitoring radioactivity. The water level of the lake Sääksjärvi is followed for local needs.
More information:
, tel. 358 9 1929 5740
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Observatory's main building
Other recording systems:
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