Ocean hemisphere geomagnetic network: Its instrumental design and perspective for long-term geomagnetic observations in the Pacific

Abstract

Geomagnetic field observations are planned and started in the Ocean Hemisphere Network Project. A new magnetometer system suitable for on-land long-term observations in remote places in the Pacific area are designed. Performance and characteristics of the magnetometers are examined through test observations, which revealed that magnetic field variation due to temperature change of the fluxgate sensor unit is the major cause for inaccuracy in three components. Analysis of test observation data indicated that the temperature 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 station are carried out. Distributions of the OHP geomagnetic stations to obtain better geomagnetic field model are examined. It was found that establishing about 10 geomagnetic stations in the Pacific will greatly improve the geomagnetic field models, and will facilitate the study of geomagnetic field distribution and variation in the Pacific. The concept of the design of the OHP magnetometer system may be applied to long-term ocean bottom magnetic observation, which is another way to cover the Earth by geomagnetic stations.