Open AccessThe Geomagnetic Spectrum For 1980 and Core‐Crustal Separation
Author(s) -
Cain Joseph C.,
Wang Zhigang,
Schmitz Dave R.,
Meyer J.
Publication year - 1989
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.1989.tb00514.x
Subject(s) - geology , earth's magnetic field , geophysics , inner core , mantle (geology) , crust , outer core , spectral density , geodesy , secular variation , radius , earth radius , core (optical fiber) , seismology , magnetic field , physics , magnetosphere , optics , statistics , mathematics , computer security , quantum mechanics , computer science
Summary The spectrum of a high degree spherical harmonic model of the geomagnetic field is analysed to compute the constants for the core and crustal field contributions. Using a noise estimate of 0.091 nT 2 at the mean Magsat radius of 6791 km, the power reduced to the Earth's surface is found to be 9.66 times 10 8 (0.286) n nT 2 for the core, and 19.1 (0.996) n nT 2 for the crust. These values show half the crustal power extrapolated to n = 0 compared with a previously published n = 23 model, and a white noise depth of only 14km below the mean surface. the core spectrum power is 30 per cent less than previously estimated and becomes flat 80 km below the core‐mantle boundary. the crustal power level is an eighth of that of an estimate based on one‐dimensional analyses of Project MAGNET survey lines. the point where the energy density of the core and crustal components become equal at the Earth's surface is n = 14.2.