Open AccessTHE SECULAR CHANGE IN THE EARTH'S MAGNETIC FIELD
Author(s) -
E. C. Bullard
Publication year - 1948
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.1948.tb02940.x
Subject(s) - secular variation , geophysics , geology , magnetic field , geodesy , earth's magnetic field , earth (classical element) , core (optical fiber) , field (mathematics) , physics , mathematics , optics , quantum mechanics , pure mathematics , mathematical physics
Summary The hypothesis that the secular change in the magnetic field of the Earth is due to electric currents induced in the material of the core by its movement through the general magnetic field of the Earth is examined. Detailed calculations are made for the focus of rapid change in South Africa. It is shown that many of the observed facts can be accounted for by a circular motion with a diameter of a few hundred kilometres situated near the surface of the core. To get numerical agreement the field at the core has to be assumed larger than seems probable. The magnetic axis of the eddy is approximately horizontal and points N. 45° W.