New Zealand and Antarctic first-order geomagnetic repeat observations 1993-1996

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McKnight, J.D. 1997 New Zealand and Antarctic first-order geomagnetic repeat observations 1993-1996. Lower Hutt: Institute of Geological & Nuclear Sciences. Institute of Geological & Nuclear Sciences science report 97/16 38 p.

Abstract: A network of stations is maintained throughout the New Zealand region and in Antarctica at which periodic (or repeat) observations of the geomagnetic field are made for the purpose of monitoring its secular variation. This report describes these repeat stations and presents the results from the second round of first-order reoccupations, conducted between 1993 and 1996. A first-order reoccupation of a repeat station involves running a portable three-component variometer near the station for a period spanning at least two nights, and making absolute observations on the station during the intervening day(s). The absolute observations are used to calibrate the variometer. An ''undisturbed'' field value for the station is determined from the calibrated variometer record to remove short period variations and records from the nearest observatory are used to remove long period variations. The difference between field values from separate reoccupations of a single station is taken as the measure of the secular variation at that station. The results of the 32 repeat station reoccupations made between October 1993 and February 1996 are given. These results include details of the absolute observations, the mean hourly values recorded by the variometer, and the ''undisturbed'' or adopted field values for each reoccupation. Descriptions of the reoccupations and information about the location of the repeat stations and access to them are also given. (auth)