Comparing the jerk with other global models of the geomagnetic field from 1960 to 1978
Abstract
About 3300 satellite values of geomagnetic intensity and about 7000 observatory values of annual mean magnetic vector components from 1960 to 1978 were fitted by three global models of the geomagnetic field B Each model includes a spatially constant external field whose time dependence is a constant plus another constant times the Dst index, and each model accepts a timeindependent station correction at each observatory. The time dependence of the internal Gauss coefficients is either cubic, quintic, or biquadratic (two independent quadratics, one before and one after January 1, 1970); and g^{0}_{1} also has an induced term proportional to the Dst index. The rms residual of the data fit is the same for the cubic and biquadratic models and insignificantly smaller for the quintic model. The quintic and biquadratic models have 1164 adjustable parameters, and the cubic has 1038. At a high level of significance the parameters of the best fitting biquadratic rule out a physical model for the magnetic impulse of 1969 in which the level surfaces of electrical conductivity in the lower mantle are approximately spherical, and also the radial magnetic field at the coremantle boundary goes from one quadratic time dependence to another in a year or less.
 Publication:

Journal of Geophysical Research
 Pub Date:
 April 1987
 DOI:
 10.1029/JB092iB05p03615
 Bibcode:
 1987JGR....92.3615B
 Keywords:

 Annual Variations;
 Geomagnetism;
 Magnetic Flux;
 Mathematical Models;
 Earth Core;
 Earth Mantle;
 Electrical Resistivity;
 Spatial Distribution;
 Time Dependence;
 Geomagnetism and Paleomagnetism: Spatial variations (all harmonics and anomalies);
 Geomagnetism and Paleomagnetism: Time variations;
 diurnal to secular