地磁长期变化信号提取和模型预测精度评估

高精度地磁场信息在地球物理导航等领域有着广泛应用,一般依靠地磁场模型来预测未来磁场的时空状态变化特征.本文基于中国大陆10个地磁基准台站2009—2022年的连续矢量观测数据,通过月均值年差分和主成分分析方法剔除外源干扰场,进一步去除岩石圈磁场,提取得到了主磁场长期变化信号,并将其与IGRF和WMM系列主磁场模型结果进行对比.通过引入绝对误差、均方根误差等指标,定量评估了IGRF-12和WMM2015模型在中国大陆区域内1—5年尺度的预测精度.结果表明,IGRF-12和WMM2015模型均能总体反映我国大陆主磁场长期变化趋势,两者总场强度的5年均方根误差分别为54.19 nT和15.86 nT,WMM2015模型预测的7个地磁要素的精度均优于IGRF-12.模型误差会随时间逐渐增大,两模型总场强度的1年期最大误差为13 nT,5年期最大误差可达153.65 nT,难以满足高精度定向钻井等领域的地磁导航需求,因此,有必要结合地磁台等观测资料,研制年周期地磁场快速长期变化模型.

Extraction of secular variation signals of geomagnetic field and evaluation of prediction accuracy of geomagnetic field models

The purpose of this research is to compare the secular variations of the core field calculated by IGRF and WMM with those observed by geomagnetic stations and to quantitatively evaluate the accuracy of IGRF-12 and WMM2015 in mainland China. Based on the hourly mean data of 10 geomagnetic reference stations in mainland China from 2009 to 2022, we used annual differences of monthly means and principal component analysis to eliminate the external interference field and remove the crustal magnetic field to extract the secular variation of the core field. The results are the prediction accuracy of the seven geomagnetic elements in the WMM2015 model is better than that of IGRF-12, and the error will gradually increase with time. The maximum 1-year error of the total field intensity of the two models is 13 nT, and the 5-year error reaches 153.65 nT, which is difficult to meet the requirements of high-precision geomagnetic navigation. It is suggested to develop the rapid secular variation model (1 year) to improve its prediction accuracy by supplementing the multi-source magnetic survey data in China.