Ocean Hemisphere Geomagnetic Network: its instrumental design and perspective for long-term geomagnetic observations in the Pacific

Geomagnetic field observations are planned and started in the Ocean Hemisph ere Network Project. A new magnetometer system suitable for on-land long-te rm observations in remote places in the Pacific area are designed. Performa nce and characteristics of the magnetometers are examined through test obse rvations, which revealed that magnetic held variation due to temperature ch ange of the fluxgate sensor unit is the major cause for inaccuracy in three components. Analysis of test observation data indicated that the temperatu re induced variations can be removed using a simple two-coefficient filter. A conservative expectation of absolute accuracy is 10 nT or less if proper temperature correction and once-a-year absolute measurement at each OHP st ation are carried out. Distributions of the OHP geomagnetic stations to obt ain better geomagnetic field model are examined. It was found that establis hing about 10 geomagnetic stations in the Pacific will greatly improve the geomagnetic field models, and will facilitate the study of geomagnetic fiel d distribution and variation in the Pacific. The concept of the design of t he OHP magnetometer system may be applied to long-term ocean bottom magneti c observation, which is another way to cover the Earth by geomagnetic stati ons.