1690-2000年地磁场能量的三维分布及其长期变化  

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

作　　者：康国发[1] 白春华[1] 李伟[1] 吴小平[1] 胡家富[1] 

机构地区：[1]云南大学地球物理系,昆明650091

出　　处：《地球物理学进展》2007年第1期80-86,共7页Progress in Geophysics

基　　金：国家自然科学基金项目(40464001);云南大学科研基金资助项目(2003Z006B)联合资助

摘　　要：利用Bloxham＆Jackson地磁场模型扣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、东向扣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，地表扣地核以外地磁场总能量及其北向扣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；偶极子扣非儡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．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 timevariation 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 r the dipole and non-dipole magnetic energy is 3780km to the core. The fact that the non-dipole ＇inagnetic 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.

关 键 词：地磁场 磁场能量 非偶极子磁场 地球内部 长期变化 

分 类 号：P318[天文地球—固体地球物理学]