Venerable, geomagnetic Observatories

When geomagnetic measurements have been going on for almost a century in the same location, all sorts of historic treasures can be found.

In Tromsø the magnetic observatory has been in operation since 1928. Here the classic variometers are still standing as they did when the last photographic recording was done in the late 1980s. One can just add photographic paper, wind the clocks, turn on the lightbeams and continue recording!

What makes the Tromsø magnetic observatory special is that there are two classic variometer setups run in parallel. The reason for this is Tromsø’s location at high latitude in the auroral zone: Owing to the large perturbations that may occur in the magnetic field during storms, the three curves on the magnetogram tend to overlap and even shift beyond the edge of the photographic paper, thus producing a mess. To mitigate this, a “storm setup” with courser resolution (tighter quartz threads) was set up to get nice recordings of the larger perturbations.

Dare I claim that the Tromsø Geomagnetic Observatory is the only historic, classic high latitude geomagnetic observatory in the world with both setups intact? Fortunately the Norwegian Government listed it with some of the other buildings at the Auroral Observatory in May this year.

Classic Variometer setup at TRO. Two Eschenhagen type variometers for H and D and a LaCour V variometer
Classic Variometer setup at TRO. Two Eschenhagen type variometers for H and D and a LaCour V variometer
The Storm setup at TRO, here all variometers are of LaCour type.
The Storm setup at TRO, here all variometers are of LaCour type.

Another venerable magnetic observatory operated by TGO is the one at Dombås (DOB) in Southern Norway. DOB is even older than the one in Tromsø started in 1916. The old variometers were in operation until 1993. Here as well, time was just frozen and a flux-gate magnetometer was put up in the room next door. Being on lower latitude this observatory did not need the storm setup.

LaCour variometer setup at Dombås
LaCour variometer setup at Dombås

At DOB the walls are blue, while they are red in Tromsø. It probably does not matter since one cannot turn on the lights anyway, since that would ruin the photographic paper!