1690～2000年地磁场能量的三维分布及其长期变化

利用Bloxham & Jackson 地磁场模型和国际参考地磁场模型(IGRF)，研究了1690～2000年地磁总能量及其北向、东向和垂直向分量的能量以及非偶极子磁场的能量在地球内部的分布及长期变化.结果表明，地表和地核以外地磁场总能量及其北向和垂直向的能量是持续衰减的，垂直向的磁场能量占总能量的64％以上，对总能量的贡献起主要作用；东向分量的能量随时间的变化以增加为主.地磁场的能量变化率存在56年的周期，主要是由偶极子磁场产生的.地表以外的非偶极子磁能从减小到增大转折出现在1770年，比地核以外滞后40年.地球内部磁能随时间的变化显示，偶极子磁能逐渐减小，非偶极子磁能增加，越靠近核幔边界增加越快；偶极子和非偶极子磁能的变化量相等的分界面在距地心3780km处.从核幔边界到地表，磁能变化的衰减非偶极子比偶极子快，表明偶极子磁场比非偶极子磁场有更深的场源.

Three-Dimensional Distribution of Geomagnetic Energy in the Earth's interior and its Secular variation for 1690-2000a

Based on the geomagnetic models of J. Bloxham & A. Jackson (BJ) and the International Geomagnetic Reference Field (IGRF), the distribution and time-variation of the geomagnetic total energy and its northern、eastern and vertical components as to that of non-dipole field in the Earth’s interior have been investigated for 1690~2000a. The results show that the total energy of geomagnetic field beyond the Earth’s core and the surface and its northern and vertical components are continually decreasing, moreover, the vertical component responsible for 64% of the geomagnetic energy plays a main role on the contribution to total energy; And the energy of the eastern component is mostly increased with time-variation. A period of 56 years mainly produced by the dipole magnetic field is existed in the changing rate of geomagnetic power. The transition from decreasing to increasing for the power of the non–dipole magnetic field beyond the core appeared on the year 1770a, 40 years later than that beyond the surface. The time-variation of geomagnetic energy shows that the dipole energy gradually drops in the Earth’s interior while goes up for the non-dipole energy and more quickly at CMB nearby; and the depth of the interface with equal change amount for the dipole and non-dipole magnetic energy is 3780km to the core. The fact that the non-dipole magnetic energy attenuation is faster than that of the dipole field indicates that there is a deeper field resource for the dipole magnetic field compared with the non-dipole magnetic field.