Sodankylä Geophysical Observatory

History of Geomagnetic observations

Short history of the instrumentation in observatory


At SGO the first instrument to measure the magnetic field was the "Eschenhagen" type variometer, made by O. Töpfer and modified by Ad. Schmidt, both in Potsdam. This instrument, also called "Töpfer", was in use until the end of 1935.

SOD 100 years ago Magnetogram 4.1.1914 noon - 5.1.1914 noon. First geomagnetic storm after official start of the operation in January 1914.

The main instrument from 1936 to 1986 was the well-known Danish "La Cour" variometer, which "quick-run" version were tested already before the Second International Polar Year held in 1932-1933. This was the last analogical instrument in operation at the geomagnetic observatory. Analogical recordings to the photography paper was stopped in 1991.

From 1986 to 2003 the main instrument of SGO was a Polish photoelectric torsion magnetometer (PSM), which was digitally recorded from the early start of operation. Today SGO's main instrument is the Danish fluxgate magnetometer (FG). As backup magnetometer of the main variometer house we still use PSM and as a secondary backup variometer in independent building we use Russian photoelecric torsion magnetometer (RM). For testing and calibration the "La Cour" was in use already since 1931, PSM since 1983, FG since 1996 and RM since 1996.

Absolute observations

For absolute measurements SGO used a "Wild-Edelmann" theodolite in 1914 and since 1915 a "Schulze" theodolite to measure the magnetic declination and the horizontal intensity. SGO had the Earth inductor "Schulze" no. 104 and the galvanometer "Schulze" no. 111 to measure the magnetic vertical intensity.

In 1952 SGO got three well-known Quartz Horizontal Magnetometers (QHM) nos 116, 117 and 118. In order to measure the vertical intensity, SGO got a new instrument BMZ (Balance Magnetomêtrique Zero) no. 31 in 1952 and no. 227 in 1959. For total intensity measurements we got the proton precession magnetometer "Elsec" type 592 no. 226 in 1965 and the proton precession magnetometer "Elsec" type 770 and "Helmholz" coil system in 1984. To measure the magnetic declination SGO got an Askania declinometer and Askania theodolite in 1965. Since 1965 the Askania theodolite was used also instead of the "Schulze" theodolite.

QHM and Ascania
The Quartz Horizontal Magnetometer (QHM) and Ascania theodolite.

In 1984 the observatory took a completely new instrument into use, namely the fluxgate magnetometer "DI-flux", "Elsec 810" to measure the magnetic declination and inclination. From 1992 all absolute measurements were done using only the DI-flux and proton precession magnetometer, which, in 2001, was replaced by a Canadian Overhauser magnetometer GSM-90. For field measurements we purchaesed a "Hungarian" theodolite with Danish electronics in 2001. In our observatory there have been several magnetometers in operation at different times, e.g. the "quick-run magnetometer La Cour" 1931-1983.

Analog measurements ended at the end of 1995.

Absolute measurement
The Helmholz coil and the proton precession magnetometer in the Absolute room,
where the magnetic field is measured once per week.

The former observers in charge since 1950s has been Dr. Eero Kataja and Mr. Johannes Kultima, who retired in 1 November 2009.

Last modified: 2019-07-05, 07:28:27.