Open AccessA Fourier Covariance Analysis of the Long Period Magnetic Field Variations in the British Isles during 1958
Author(s) -
Lamden R. J.
Publication year - 1970
Publication title -
geophysical journal of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0016-8009
DOI - 10.1111/j.1365-246x.1970.tb06062.x
Subject(s) - covariance , ellipse , fourier analysis , geodesy , plane (geometry) , fourier transform , geology , variation (astronomy) , field (mathematics) , physics , mathematics , geometry , mathematical analysis , statistics , astrophysics , pure mathematics
Summary A Fourier analysis has been made of the magnetic variations in X , Y , Z at four British observatories during the year 1958 January 1‐December 31. The spatial variation of activity has been determined by computing covariance spectra for each component, X , Y , Z , measured at four observatories. These serve to define a plane surface which represents the average field distribution. A length scale for the disturbances can be found from the way in which the covariance changes with distance. By comparing different vectors, H , Z and Y , X measured at the same station, an activity ellipse can be defined. This shows significant regional changes which may be ascribable to crustal conductivity variations.