IGRF-11描述的2005-2010年中国地区地磁长期变化及其误差分析

Geomagnetic secular variation in China during 2005-2010 described by IGRF-11 and its error analysis

第11代国际地磁参考场(IGRF-11)是国际地磁学与高空物理学联合会(IAGA)于2009年12月提出的最新与比较准确的IGRF.根据IGRF-11模型,计算了2005-2010年中国地区地磁长期变化(SVC).IGRF-11所描述的2005-2010年中国地区地磁长期变化与实际观测的地磁长期变化(SVO)是基本一致的,但亦有明显差异.分析比较了在中国地区34个台站上的SVO与SVC之间的差异,并得到了它们之间的差值及其均方误差σ,对于地磁偏角和倾角,σ分别为0.35′/a与0.53′/a;对于地磁总强度、水平分量、北向分量、东向分量与垂直分量,σ分别为5.12nT/a,8.91nT/a,8.89nT/a,3.27nT/a与3.59nT/a.引起IGRF-11所描述的2005-2010年中国地区地磁长期变化的误差原因是:中国地区的区域性与局部性的磁异常、IGRF忽略了外源场与IGRF模型的截断阶数、全球台站与测点的分布不均匀、地磁观测误差等因素.由于中国地磁模型(CGM)优于IGRF模型,并能比较准确地描述中国地区地磁场及其长期变化,故在实际应用中应选用CGM.

The eleventh generation International Geomagnetic Reference Field（IGRF-11） was issued in December 2009 by the International Association of Geomagnetism and Aeronomy（IAGA）.The IGRF-11 is the latest and comparatively precise IGRF.According to the IGRF-11 model,the geomagnetic secular variation（SVC） in China during 2005-2010 was calculated.The SVC and the geomagnetic secular variation（SVO） obtained from the geomagnetic data of practical observations in China are basically consistent,but there is obvious difference.The SVO and SVC at 34 observatories in China were analyzed and compared;the differences between the SVO and SVC and the mean square roots σ were obtained.The mean square roots σ are 0.35 ′/a and 0.53 ′/a for geomagnetic declination and inclination respectively;and the σ are 5.12 nT/a,8.91 nT/a,8.89 nT/a,3.27 nT/a and 3.59 nT/a for geomagnetic total intensity,horizontal component,northern component,eastern component and vertical component respectively.The reasons for the error of the geomagnetic secular variation in China during 2005-2010 described by the IGRF-11 are the regional and local magnetic anomalies in China,no external source field for the IGRF and the truncation order of the IGRF,non-homogeneous distribution of the geomagnetic observatories,stations and sites in the world,the errors of geomagnetic observations etc.The China geomagnetic model（CGM） should be used in practical application,because the CGM is better than the IGRF and can describe the geomagnetic field and its secular variation in China with comparative precision.