Ocean Hemisphere Project Geomagnetic Data General The magnetic field observation in the Ocean Hemisphere Project was started in 1997. The magnetometer, RPF-532 by Tierra Technica, is consisted of a set of fluxgate sensor (three vector components), a proton precession sensor (intensity) and a thermometer attatched to the fluxgate sensor unit. The magnetometer sytem is designed for almost automatic long-term geomagnetic observations. Details of the design and properties of the magnetometer system may be found in the following paper: Shimizu H. and H. Utada (1999), Ocean Hemisphere Geomagnetic Network: its instrumental design and perspective for long-term geomagnetic observations in the Pacific. Earth Planets Space, 51, 917-932. The fluxgate sensor is aligned to local geomagnetic north as usual geomagnetic observations, and the magnetic field data found in this homepage are in geomagnetic coordinate, Hx (geomagnetic +North-South), Hy (geomagnetic +East-West), and Hz (+Downward-Upward). Refering to the results of absolute observations, which may be also downloaded from this homepage, will be necessary to recover the direction and actual strength of the vector components. Data Format The data files consist of two-line header information and following magnetic field data. The following is an example of the first several lines of the data files. ======= example data : Ponape, Jan, 1999 ===== Ponape 199901 31 38700 0 -1000 90.57 217.15 7.68 38263.9 28.620 91.12 217.14 7.74 38267.3 28.620 91.36 217.11 7.70 38217.9 28.620 91.26 217.21 7.51 38173.6 28.620 90.98 217.28 7.33 38263.4 28.620 90.85 217.45 7.17 38131.5 28.620 89.62 217.37 6.87 38272.2 28.620 88.55 217.22 6.73 38261.1 28.620 . . . . . ===== end of example data ===== - Header Information The first line shows station name (Ponape), year-month (199901), and number of days (31) in the month. The second line contains the information of the bias values for Hx (38700), Hy (0), and Hz (-1000). The formats of the first two lines are, in FORTRAN form, format(a15,i7,i3) format(3i6) - Observed Field One-minute values of the variation part of vector data (the first three colums for Hx, Hy, and Hz, respectively), total intensity measured by proton magnetometer (fourth column) and temperature (fifth column) are shown in the following lines. The first minute of the data files (the first line of the data part, the third line in total) is 00:00:00 UT of the first day of the month. To recover vector data from the fluxgate sensor unit, add the bias value and variation part. (For example, Hx=38700+90.57, Hy=0 + 217.15, Hz=-1000+7.68 for the first minute [00:00:00 of Jan. 1, 1999 UT].) The data part should contain 1440*[number of days] lines. The format of the data part is, in FORTRAN form, format(3f7.2,f9.1,f7.3) If you have any questions regarding the magnetic field data, please write to Hisayoshi Shimizu: shimizu@eri.u-tokyo.ac.jp Hisayoshi Shimizu Earthequake Research Institute University of Tokyo Yayoi 1-1-1, Bunkyo-ku Tokyo, 113-0032 JAPAN shimizu@eri.u-tokyo.ac.jp