The geomagnetic field in New Zealand at epoch 1970.5

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Reilly, W.I.; Burrows, A.L. 1973 The geomagnetic field in New Zealand at epoch 1970.5. [s.l.]: [s.n.]. DSIR Bulletin 211. 43 p.

Abstract: Observations of the magnetic vector between 1940 and 1970 have been used in the least-squares determination of the geomagnetic normal field for the New Zealand region, expressed as an analytic function of geographic co-ordinates and time involving 26 coefficients. The observational data comprise a total of 708 vector determinations at 211 magnetic stations in New Zealand and outlying islands, at 269 points on `Project Magnet' survey flight lines over the surrounding oceans, and at Amberley, Apia, Toolangi, and Macquarie Island Observatories. The results are given in the form of contour maps of the seven normal field elements at epoch 1970.5, the maps covering an area from 33 deg. to 53 deg.S latitude, and 165 deg. to 185 deg.E longitude. Also given are the values of the 26 numerical coefficients in the expression for the normal field, and the values of the observed and residual magnetic vector for each observation. Mean station residuals for each element are shown on the contour maps. A comparison of the present normal field charts with those of earlier epochs shows that the new method of analysis has produced significant changes only in the representation of the easterly force (Y) and declination (D) in the North Island, and this is due to adoption of a criterion of consistency between X and Y (or D and H). A further comparison between the present normal field and that predicted from the parameters of the International Geomagnetic Reference Field 1965.0 shows such discrepancies as to suggest that the latter does not give an adequate representation of the geomagnetic field in the New Zealand region. (auth)


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