The physical decomposition of the Earth's permanent magnetic field—No. I. the assumed normal magnetization and the characteristics of the resulting residual field
Abstract
The object of this paper is to resolve the earth's so-called permanent field into component ones physically interpretable. It is an elaboration of a preliminary communication read in 1896 before the American Association for the Advancement of Science and the British Association, and entitled “On the Component Fields of the Earth's Permanent Magnetism”2 In this first paper the deductions were based on the measured magnetic components at 84 symmetrically distributed points; namely, at the intersections of meridians 30° apart, with the parallels of latitude ±60°, ±40°, ±20°, and the equator. The present investigation, on the other hand, depends upon the measured magnetic components at 1800 points, situated at the intersections of meridians, 5° apart, with the 5° parallels between 60°N. and 60°S.If we take a cursory glance at a series of magnetic charts of the Earth, we are at once impressed with the complexity of the distribution of its magnetism. Turn to an isogonic chart, for instance, and behold the peculiar condition of things existing at the present time in Eastern China and Japan. You will note that here we have a closed curve along which the needle is “true to the pole.” Within the oval the needle everywhere points W. of N., while outside, the compass everywhere bears East. What is the cause of the peculiar distribution in this region? Is it due, for example, to peculiarities in the geological structure of this part of the earth? We find, moreover, that this oval is not a permanent feature of that region. It has formed only within the present century, and is now enlarging. In the sixteenth century we had a somewhat similar state of affairs in the Atlantic Ocean, only that in this case the oval inclosed places where the needle stood East, instead of West as in the Asiatic oval.
- Publication:
-
Terrestrial Magnetism and Atmospheric Electricity
- Pub Date:
- 1899
- DOI:
- 10.1029/TE004i001p00033
- Bibcode:
- 1899TeMAE...4...33B