Geomagnetics

Variations of the three components of the geomagnetic field are recorded using two 3-axis fluxgate systems (FGE fluxgate magnetometer from DTU Space, Copenhagen and a DM-100 3-axis fluxgate sensor from STL Systemtechnik Ludwig GmbH, Konstanz). They are orientated sligtly different, one is orientated referring to geomagnetic North and the second one is alligned referring to geographic North. Total intensity is measured with a GSM 19-1 Overhauser proton precession magnetometer. All instruments sample at a 1-second interval. Every 3-4 days declination and inclination of the geomagnetic field is measured manually using a non -magnetic theodolite (Carl Zeiss-20A/B) with a single-axis fluxgate sensor mounted on the telescope. Geographic North direction is determined typically once a month using a gyro compass (WILD GAK-1) mounted on top of the theodolite. The manually determined angles D and I are needed for calibration of the relative fluxgate data. Therefore these measurements have to be carried out always with the highest possible accuracy. Once in a month the geographic North direction has to be determined since we don't have an external azimuth for reference. This is done using a gyro compass (WILD GAK-1) which can be mounted on top of the theodolite. Since 2015 we have been testing an allsky camera for imaging polar lights. At this very beginning stage it is a low budget camera by which we want first to find out if we can obtain at all pictures of the night sky and polar lights with sufficient quality (influence of backscattering of station illumination). First results seem promising.

Data access

All recordings are transferred online from NM-III to AWI in Bremerhaven and from there further on to Niemegk observatory which belongs to GFZ, Potsdam, and also to INTERMAGNET. Plots of calibrated and first adjusted minute means can be generated on request and data. Hourly mean values are archived at the world data center WDC-1 in Edinbourgh. Geomagnetic field variations can also be viewed and downloaded at the  AWI-website.

 

Links:

GFZ

INTERMAGNET

Construction of the observatory

Because NM-III was built about 5 km away from the former Neumayer-II there was also the need for a new construction of the geomagnetic observatory.  The observatory is located some 1.5 km south of NM-III and installed in a deep trench in the firn. The trench is 12 meters long, 5 meters wide and the original depth from the surface to the bottom measured about 8 meters. The trench was covered by strong wooden construction beams and plywood boards.

 

 

 

Observatory

Access to the observatory is possible climbing down a ladder in a vertical entrance shaft. Currently the bottom of the trench is approx. 12 meters below the snow surface. Because of an annual snow accumulation of approx. 1.5 meters the roof of the trench is increasingly depressed. Recording electronics, computers and STL and GSM sensors are installed inside a heated and thermally insulated container. The 3-axis FGE magnetometer is resting outside the container on top of a plastic sewage tube deeply frozen into the snow. All construction materials used are strictly non-magnetic. The broadband seismometer, which is also non-magnetic, is installed at one front end of the trench in a small niche cut into the snow wall. A guidance rope will assist for a safe walk between the base and the observatory when visibility is low during white out conditions, heavy storms or in the dark winter time.