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Ocean Hemisphere Geomagnetic Network: its instrumental design and perspective for long-term geomagnetic observations in the Pacific
Earth, Planets and Space volume 51, pages 917–932 (1999)
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.
Achache, J., J. L. LeMouël, and V. Courtillot, Long-period geomagnetic variations and mantle conductivity: an inversion using Bailey’s method, Geophys. J. R. astr. Soc., 65, 579–601, 1981.
Banks, R. J., Geomagnetic variations and the electrical conductivity of the upper mantle, Geophys. J. R. astr. Soc., 17, 457–487, 1969.
Barton, C. E., R. T. Baldwin, D. R. Barraclough, S. Bushati, M. Chiappini, Y. Cohen, R. Coleman, G. Hulot, P. Kotze, V. P. Golovkov, A. Jackson, R. A. Langel, F. J. Lowes, D. J. McKnight, S. Macmillan, L. R. Newitt, N. W. Peddie, J. M. Quinn, and T. J. Sabaka, International Geomagnetic Reference Field, 1995 revision presented by IAGA Division V, Working Group 8, Phys. Earth Planet. Inter, 97, 23–26, 1996.
Bloxham, J. and D. Gubbins, The secular variation of Earth’s magnetic field, Nature, 317, 777–781, 1985.
Chave, A. D., A. W. Green, R. L. Evans, J. H. Filloux, L. K. Law, R. A. Petitt, Jr., J. L. Rasson, A. Schultz, F. N. Spiess, P. Tarits, M. Tivey, and S. C. Webb, Report of a workshop on technical approaches to construction of a seafloor geomagnetic observatory, Woods Hole Oceanographic Inst. Tech. Rep., WHOI-95-12, 43 pp., 1995.
Forbes, A. J., General Instrumentation, in Geomagnetism vol. 1, edited by J. Jacobs, pp. 51–142, Academic Press, 1987.
Fukao, Y, The Ocean Hemisphere Network Project, Proc. OHP International Symp., 9, 1997.
Gubbins, D. and J. Bloxham, Geomagnetic field analysis—III. Magnetic fields on the core-mantle boundary, Geophys. J. R. astr. Soc., 80, 695–713, 1985.
Langel, R. A., The main field, in Geomagnetism vol. 1, edited by J. Jacobs, pp. 249–512, Academic Press, 1987.
Langel, R. A., R. T. Baldwin, and A. W. Green, Toward and improved distribution of magnetic observatories for modeling of the main geomagnetic field and its temporal change, J. Geomag. Geoelectr, 47, 475–508, 1995.
Merrill, R. T., M. W. McElhinny, and P. L. McFadden, The Magnetic Field of the Earth, 531 pp., Academic Press, 1996.
Schultz, A. and J. C. Larsen, On the electrical conductivity of the mid-mantle—I. Calculation of equivalent scalar magnetotelluric response functions, Geophys. J. R. astr. Soc., 88, 733–761, 1987.
Schultz, A. and T. S. Zhang, Regularized spherical harmonic analysis and the 3-D electromagnetic response of the Earth, Geophys. J. Int., 116, 141–156, 1994.
Shimizu, H., T. Koyama, and H. Utada, An observational constraint on the strength of the toroidal magnetic field at the CMB by time variations of submarine cable voltages, Geophys. Res. Lett., 25, 4023–4026, 1998.
Toh, H., T. Goto, and Y. Hamano, A new seafloor electromagnetic station with an Overhauser magnetometer, a magnetotelluric variograph and an acoustic telemetry modem, Earth Planets Space, 50, 895–904, 1998.
Trigg, D. F., P. H. Serson, and P. A. Camfield, A solid state electrical recording magnetometer, Pub. Earth Phys. Branch (Geol. Surv. Canda), 41, 5, 1971.
Yokoyama, Y. and T. Yukutake, Sixty year variation in a time series of the geomagnetic Gauss coefficients between 1910 and 1983, J. Geomag. Geoelectr, 43, 563–584, 1991.
Yumoto, K. and the 210° MM Magnetic Observation Group, The STEP 210° magnetic meridian network project, J. Geomag. Geoelectr, 48, 1297–1309, 1996.
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Shimizu, H., Utada, H. Ocean Hemisphere Geomagnetic Network: its instrumental design and perspective for long-term geomagnetic observations in the Pacific. Earth Planet Sp 51, 917–932 (1999). https://doi.org/10.1186/BF03351563
- Secular Variation
- Temperature Correction
- Sensor Unit
- Power Supply Unit
- Geomagnetic Variation