51. The Non-dipole Part of the Earth's Magnetic Field

概要

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The non-dipole parts of the earth's magnetic field were synthesized from spherical harmonic coefficients for various epochs, going back to the 16th century. Time variations in the non-dipole fields were then examined. The distribution of the non-dipole field in the northern hemisphere seems to have undergone a great change in the 18th century. Since then, the main features of the non-dipole field have remained nearly the same. Examination of individual non-dipole anomalies revealed the existence of three types of regional anomalies. One is the anomaly drifting westwards. The second one is that staying nearly at the same place but changing its intensity. The third type is the anomaly standing still with constant intensity. It has been revealed that only a few anomalies belong to the first type and that most of the anomalies remain at the same position and belong to the second or third type anomaly.|地球磁場の球函数解析は,既に1550年の磁場分布に対してFritscheが実施している.この報告では,展開係数より逆に非双板子磁場を合成して,その時間変化を調べた.
1968-12-20