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Summary. In the maximum entropy spectrum analysis (MESA) of geomagnetic data, the required order can be estimated by the zero‐frequency half‐power width (ZHW) minimum method proposed in this paper. The spectra of the data for 1876–1975 at Zo‐se showed a period of 40yr, in addition to the well‐known periods. The amplitudes of the variations were estimated with parabolic‐sinusoidal series fitting.

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This is a brief account of a proposed observational program to be carried out in China during IMS. It consists mainly of four parts: (1) reform and reinforcement of the existing stations, (2) installation of new equipment for IMS, (3) analysis of IMS data and study of STP, and (4) coordination of scientific activities at home and abroad. Altogether, 16 items are proposed. For the realization of these four modernization projects we should like to learn everything good for us. But now, I want to take this opportunity to talk about an observational program, which I proposed to the Academy several months ago, to be carried out in China during IMS.

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