Abstract
The paper makes a new contribution to the problem of separation of magnetovariation fields, observed over a limited area of the Earth's surface, into parts of external and internal origins. It is shown that there are important advantages in making such separations in the wavenumber domain, making use of the orthogonality of external and internal parts. The method uses a unified potential both for the adjustment of data to minimize their curl, and in the separation process. The technique is tested by combining the analytically calculated fields of line currents above and below the plane of “observation”, separating them and comparing the separated field components with the known original fields. While the precision is limited by known effects of the limited area covered by the data, satisfactory correlation coefficients are obtained between separated and original fields. The new separation technique is finally applied to a magnetovariation event recorded in a recent array study in western Canada, and it is shown that a prominent anomaly is caused by internal currents.
