Magnetometer Sodankylä Geophysical Observatory

The Sodankylä Geophysical Observatory has been in operation since 1914. Nowadays the observatory runs continuously three vector magnetometers: a Danish fluxgate magnetometer (FG) and two photoelectric torsion magnetometers, a Polish model (called as PSM) and a Russian model (called as RM).

The FG has been in operation since 1996, the PSM since 1983 and the RM since 1996. The PSM was first digitally sampled magnetometer sampled every 15 seconds. 2Hz sampling with 20-bit AD-converters was started in late 1995.

Additionally, there are three magnetometers to measure the total magnetic field: Canadian GEM GSM-90 and GSM-90F1 Overhauser magnetometers and old proton precision magnetometer (PPM) Elsec 770 , which is nowadays used only during field measurements and difference checks at the observatory.

For DI-absolute measurements (typically once a week) there are two DI-fluxgate magnetometers installed on magnetically clean Zeiss Jena 010A theodolites. SGO also participates to the regular DI-absolute observations of IMAGE sites in Northern Finland.

The Danish DMI flux gate magnetometer (FG) has been used for the definitive data of SOD since 1 Jan 2003, when it replaced PSM as a main instrument. The Polish photo torsion magnetometer (PTM) has continued as first backup instrument at the main variometer house. The Russian magnetometer runs in backup variometer house nearby the control house of the geomagnetic observatory. The sampling rate of the FG, PSM and RM magneometers is 2 Hz. Due to impulse response of the instruments the data is suitable with for the periods longer than 3 seconds. The Overhauser magnetometer GEM GSM-90 has a sampling rate of 0.2 Hz.