New Zealand first order geomagnetic repeat observations 2007-2009

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Bennie, S.L. 2010 New Zealand first order geomagnetic repeat observations 2007-2009 Lower Hutt, N.Z.: GNS Science. GNS Science report 2010/60 20 p.

Abstract: A network of stations is maintained throughout the New Zealand region at which periodic (repeat) observations of the geomagnetic field are made for the purpose of monitoring the secular variation. Since 2000 the observations have been focussed on three key sites of the network, Kaitaia, Gisborne and Invercargill. This report describes the three key sites and gives the results of repeat observations at two of these sites – Kaitaia and Invercargill. The re-occupation of a repeat station involves running a portable three component variometer, near the repeat station, to measure the variations in the vector magnetic field. The variometer is run for at least two nights and the absolute observations of the magnetic field are made during the intervening day(s). These “instantaneous” absolute observations are used to calibrate the variometer record. The normal “undisturbed” field value for each station is determined by taking the night-time calibrated variometer values and referencing these to the corresponding values from the Eyrewell Magnetic Observatory near Christchurch. The results of the two repeat station re-occupations are presented. These include the absolute observations and mean hourly values recorded by the variometer. (auth/DG)