Residual geomagnetic field from the satellite Cosmos 49

Abstract

The residual field from Cosmos 49 is presented in chart form. This map displays vast areas (1000–4000 km across) of negative and positive ΔT (the T are differences between measured and model fields) that are of the order of a few tens of gammas. The external field does not exert any essential influence on the ΔT distribution. The frequency spectrum of ΔT is similar to that of the model field used for the greater part of the chart, but within the ‘contrast zones’ the ΔT spectrum contains higher harmonics. There is no apparent correlation between the ΔT distribution and near‐surface anomalies or the thickness of the magnetoactive layer of the earth's crust. The correlation with heat flow distribution is somewhat more distinct within certain regions. It appears that the greater part of ΔT is due to a poor representation of the main geomagnetic field. However, the authors do not exclude the possibility of intermediate anomalies of inductive origin within the mantle, which could contribute to the higher‐frequency part of the ΔT spectrum.

A global magnetic anomaly map

“…The resolution of this map permits the identification of anomalies with wavelengths less than 140. This represents a substantial increase in resolution over previous analyses (Benkova et al, 1973;Regan et al, 1973b). The anomalies noted on these earlier maps termed "intermediate size" anomalies, were of half wavelengths of approximately 190 and not clearly of lithospheric origin.…”

The Geomagnetic Spectrum For 1980 and Core-Crustal Separation

“…The fact that there is a complex relationship between the spectrum of the potential function and that of the scalar field was first noted by Benkova, Dolginov & Simonenko (1973), and later amplified by and Hamson & Carle (1982). The poor correspondence between the one-dimensional scalar survey results and those from spherical analyses is further indication that the use of two-dimensional geomagnetic 'spatial' spectrum (i.e.…”

The Use of Geomagnetic Field Models in Magnetic Surveys

“…Each value of n in the spherical harmonic expansion is a global wavenumber; that is, each harmonic represents variations of the potential whose wavelengths are approximately 40,000/n kilometers. This is not strictly true for the variations of the total field, for as has been pointed out by Benkova et al (1973), the total field variations are not exactly identical with those of the potentail but may be "smeared" by several degrees (n). Still, the complexity of a field model is determined by its maximum degree, so that a high n* permits modeling smaller wavelength components of the field.…”