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Geoscientific Instrumentation, Methods and Data Systems An interactive open-access journal of the European Geosciences Union

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https://doi.org/10.5194/gi-2017-15
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
15 May 2017
Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Geoscientific Instrumentation, Methods and Data Systems (GI).
Merging Fluxgate and Induction Coil Data to produce low Noise geomagnetic Observatory Data meeting the INTERMAGNET Definitive One-second Data Standard
Heinz-Peter Brunke1, Rudolf Widmer-Schnidrig2, and Monika Korte1 1GeoForschungsZentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany
2Black Forest Observatory, Heubach 207, 77709 Wolfach
Abstract. For frequencies above 30 mHz the instrument intrinsic noise level of typical fluxgate magnetometers used at geomagnetic observatories can mask ambient magnetic field variations on magnetically quiet days. This is especially true for stations located at mid- and low-latitudes where variations are generally smaller than at high latitudes. INTERMAGNET has set a minimum quality standard for definitive one second data. Natural field variations referred to as pulsations (Pc-1, Pc-2, Pi-1) fall in this 5 band. Usually their intensity is so small, that they rarely surpass the instrumental noise of fluxgate magnetometers. Moreover high quality magnetic field observations in the band 30 mHz–0.5 Hz contain interesting information, e.g. for the study of ionospheric electron interactions with electromagnetic ion cyclotron (EMIC) plasma waves.

We propose a method to improve 1 Hz observatory data by merging data from proven and tested fluxgate magnetometers with induction coil magnetometers into a single data stream.We show how measurements of both instruments can be combined without information loss or phase distortion.

The result is a time series of the magnetic field vector components, combining the benefits of both instruments: long term stability (fluxgate) and low noise at high frequencies (induction coil). This new data stream fits perfectly into the data management procedures of INTERMAGNET and meets the requirements defined in the Definitive One-second Data Standard. We describe the applied algorithm and validate the result by comparing power spectra of the fluxgate magnetometer output with the merged signal. Daily spectrograms from the Niemegk observatory (NGK) show that the resulting data series reveal information at frequencies above 0.05 Hz that can not be seen in raw fluxgate data.


Citation: Brunke, H.-P., Widmer-Schnidrig, R., and Korte, M.: Merging Fluxgate and Induction Coil Data to produce low Noise geomagnetic Observatory Data meeting the INTERMAGNET Definitive One-second Data Standard, Geosci. Instrum. Method. Data Syst. Discuss., https://doi.org/10.5194/gi-2017-15, in review, 2017.
Heinz-Peter Brunke et al.
Heinz-Peter Brunke et al.
Heinz-Peter Brunke et al.

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Short summary
In magnetic observatory data according to the INTERMAGNET Definitive One-second Data Standard the fluxgate magnetometer self noise usually covers the natural signal for frequencies higher than about 30 mHz. We present a numerical method how to merge the data with induction coil data in order to drastically reduce noise and to fill the entire possible bandwidth with information on the earth magnetic field. In spectrograms we visualize interesting phenomena revealed with the method.
In magnetic observatory data according to the INTERMAGNET Definitive One-second Data Standard...
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