京津冀地区地磁场球冠谐分析

2002年在京津冀地区进行了45个测点的地磁三分量测量，对测量资料进行通化处理，通化时间为2002年5月5日16～18时（世界时）. 通化后的观测均方差分别优于1.5nT（地磁场总强度F），0.5′(磁偏角D和磁倾角I). 将国际参考地磁场（IGRF2000）作为地磁正常场，建立了京津冀地区地磁异常场的球冠谐模型（BTHASCH）. 球冠极的空间位置坐标为39.5°N和117.0°E，球冠半角为4°. 在模型计算过程中，球冠谐函数的截断阶数分别取为1～10. 经综合比较， 最终采用的截断阶数为5. 建立了京津冀地区参考地磁场的球冠谐模型（BTHGRF）.根据模型，绘制了京津冀地区地磁异常场图(ΔX、ΔY、ΔZ、ΔF、ΔD、ΔI)和京津冀地区地磁图(X、Y、Z、F、D、I).

SPHERICAL CAP HARMONIC ANALYSIS OF THE GEOMAGNETIC FIELD IN THE BEIJING-TIANJIN-HEBEI REGION

The three component absolute survey of the geomagnetic field at 45 field sites was carried out in the Beijing Tianjin Hebei region in 2002. The survey data were reduced, and the reduced time was 16:00～18:00(UT) on May 5, 2002. The RMS values after reducing are better than 1.5nT(for total intensity F) and 0.5′(for declination D and inclination I, respectively). Taking IGRF2000 as the main normal field in the region, the spherical cap harmonic models（BTHASCH）of the anomaly geomagnetic field in the region are established. The spherical cap harmonic models（BTHGRF）of the geomagnetic reference field in the region are calculated also. The pole of the spherical cap is at 39.5°N and 117.0°E, and its half angle is 4°. During the model calculation, the truncation order is taken from 1 to 10. According to comparison of results, the final truncation order is taken as 5. Using this model, the geomagnetic charts (X, Y, Z, F, D, and I) and the anomaly charts (ΔX,ΔY,ΔZ,ΔF,ΔD, and ΔI) in the region are produced.