engleski

Reduction practices in recent Croatian Geomagnetic RepeatStations Network surveys

In circumstance of no national geomagnetic observatory and no on-site variometer, two approaches to reduction were investigated on Croatian Geomagnetic Repeat Stations Network surveys data of 2004 and 2007. These data were reduced to 2004.5 and 2007.5 epochs by simple and a proposed method, assuming the secular variations at the observatory and repeat station were equal and different, respectively. In proposed method, the annual variation of the field element at the repeat station was estimated as the difference between the values for 2007 and 2004, and assumed to be the constant in the time interval between the measurements in 2004 and 2007. These reductions, derived in reference to L’Aquila, Fürstenfeldbruck and Tihany observatories, and corresponding weighted and non-weighted averages, were compared and found close to each other.

geomagnetic data reduction; annual variation

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