Open AccessOn the azimuthally dependent contribution of crustal magnetization to the magnetic field
Author(s) -
Lesur Vincent
Publication year - 2000
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 - 10.1046/j.1365-246x.2000.00191.x
Subject(s) - magnetization , remanence , field (mathematics) , magnetic field , geophysics , condensed matter physics , orbital magnetization , physics , magnetic anisotropy , geology , mathematics , quantum mechanics , pure mathematics
The way in which induced or remanent magnetization contributes to the crustal magnetic field at a point r on or above the Earth's surface is investigated. It is shown that only smoothly varying components of magnetization along an azimuth φ about r contribute to the crustal magnetic field. Stated mathematically, if the distribution of magnetization is expanded in a discrete Fourier basis in φ , only wavenumbers k =0, ±1, ±2 contribute to the crustal field. On the other hand, there is no such simplifying expansion of the magnetization distribution in the radial direction. In the case where the induced magnetic field is due to a local variation of susceptibility in a smooth inducing field such as the core field, this result can be extended to the distribution of susceptibility itself. Then, when induced and inducing magnetic field vectors are defined in the same local spherical system of coordinates, the matrix relating these two fields presents a very well‐defined and simple structure.