A study on variations of non-dipole magnetic field over Chinese mainland during 2000 BC to 1990 AD  

作　　者：FENG Yan JIANG Yong SUN Han AN ZhenChang MAO Fei 

机构地区：[1]The College of Math & Physics, Nanjing University of Information Science & Technology [2]Remote Sensing Application and Experiment Station of National Satellite Meteorological Center [3]Institute of Geology and Geophysics,Chinese Academy of Sciences [4]Chinese Academy of Meteorological Sciences

出　　处：《Science China Earth Sciences》2014年第6期1229-1244,共16页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant No.41174165);Special Project for Meteo-scientific Research in the Public Interest(Grant No.GYHY201306073-2,GYHY200906033);Science Research Project of NUIST(Grant No.20110420)

摘　　要：We calculated and analyzed variation of the non-dipole(ND)magnetic field at the millennium scale over the Chinese mainland during 2000 BC–1900 AD using the newest global geomagnetic model,CALS3K.4(3K.4).The newest-generation IGRF(IGRF11)was used to verify the results.Taking component Z for example,we calculated and analyzed the distribution and annual change rates of the ND field during 1900–1990 AD every 5 yr,using two models.To thoroughly analyze the contributions of field sources,quadrupole and octupole fields,and others within the ND field at the surface and core-mantle boundary(CMB)were investigated.Results show that there were three main variation phases of the field during the period 2000BC–1900 AD.The mean amplitude roughly reflected the ND field because of the distribution and variation of that field,corresponding somewhat to the mean amplitude change.A magnetic anomaly of the ND field over East Asia(EA)first emerged in 1682 AD,and its extreme intensity had increased a total of 15276.95 nT by 1900 AD.Its location moved continuously southeastward after 1690 AD.The asymmetry between location and intensity of extreme points over EA,particularly during1740–1760 AD,indicates irregularity of fluid motion inside the outer core.Mean annual changes of Z are generally divided into four phases,which first oscillated between 2000 and 800 BC,then increased,decreased and increased in the periods 800BC–300 AD,300–900 AD and 900–1900 AD,respectively.The intensity of mean annual change increased a total of 22.87nT/yr.Anomaly extreme locations based on 3K.4 and IGRF11 over EA centered around 44°N and 103°E for degree(n)greater than 5,and intensities continuously increased with n.During 2000 BC–1990 AD,ND energy of Z at the surface and CMB had decreased in total by 18.29%and 23.23%,respectively.The field source of 26–210 pole fields are more or less affected by the lithospheric field.Energies of higher degree at the surface attenuate by almost 99%compared with CMB,but mean attenuation speeds of the low-We calculated and analyzed variation of the non-dipole（ND） magnetic field at the millennium scale over the Chinese mainland during 2000 BC–1900 AD using the newest global geomagnetic model, CALS3K.4（3K.4）. The newest-generation IGRF（IGRF11） was used to verify the results. Taking component Z for example, we calculated and analyzed the distribution and annual change rates of the ND field during 1900–1990 AD every 5 yr, using two models. To thoroughly analyze the contributions of field sources, quadrupole and octupole fields, and others within the ND field at the surface and core-mantle boundary（CMB） were investigated. Results show that there were three main variation phases of the field during the period 2000 BC–1900 AD. The mean amplitude roughly reflected the ND field because of the distribution and variation of that field, corresponding somewhat to the mean amplitude change. A magnetic anomaly of the ND field over East Asia（EA） first emerged in 1682 AD, and its extreme intensity had increased a total of 15276.95 nT by 1900 AD. Its location moved continuously southeastward after 1690 AD. The asymmetry between location and intensity of extreme points over EA, particularly during 1740–1760 AD, indicates irregularity of fluid motion inside the outer core. Mean annual changes of Z are generally divided into four phases, which first oscillated between 2000 and 800 BC, then increased, decreased and increased in the periods 800 BC–300 AD, 300–900 AD and 900–1900 AD, respectively. The intensity of mean annual change increased a total of 22.87 nT/yr. Anomaly extreme locations based on 3K.4 and IGRF11 over EA centered around 44°N and 103°E for degree（n） greater than 5, and intensities continuously increased with n. During 2000 BC–1990 AD, ND energy of Z at the surface and CMB had decreased in total by 18.29% and 23.23%, respectively. The field source of 26–210 pole fields are more or less affected by the lithospheric field. Energies of higher degree at the surface attenuate by al

关 键 词：non-dipole geomagnetic field CALS3K.4 IGRF11 

分 类 号：P318.4[天文地球—固体地球物理学]