  Based on satellite data, both large and small-scale flows were identified on
the core surface .At the same time, the observed rapid decrease in the dipole
component of the main geomagnetic field does not find a satisfactory
explanation. In the previous papers we carried out the comparative studies of
the structure of the lowest mantle with the motion path of the small size
current loops approximating the MGF's small-scale anomalies. The hypothesis was
stated that heterogeneities in the lowest mantle structure and the topographic
irregularities of the core-mantle boundary associated with ancient subduction
zones is one of the primarily responsible for the small-scale vortices
formation and the local MGF variation. In this paper, we carry out the
analogous comparison for the large scale sources approximating the nondipole
part of the geomagnetic field.
