中国地区地磁场水平梯度的计算与分析

Calculation and analysis of geomagnetic field horizontal gradients in China

根据2000年中国地区156个地磁台站和复测点的实测数据以及国境外的6个地磁台站实测数据,加上国境外36个IGRF点,分别利用Taylor多项式模型和曲面Spline模型,建立了中国地区地磁场总强度(F)、磁偏角(D)和磁倾角(I)的地磁模型,通过对两种模型中各分量的ψ(纬度)和λ(经度)进行微分,计算得到F、D、I的水平梯度值,并绘制相应分量沿南北方向和东西方向的水平梯度图,将其与2000年IGRF10的水平梯度图作比较,最后对水平梯度的空间分布以及三种梯度图进行了分析比较.结果表明:F和I的水平梯度主要随纬度变化,F随纬度增加,变幅约为7.0～6.0nT/min,在中部地区(25°～35°N,90°～120°E)强度达到最大;I随纬度的增加,变幅约为2′/min～1′/min;D的水平梯度随纬度和经度而变化,随着经度和纬度的增加,变幅分别约为0.4′/min～—0.3′/min和—0.1′/min～—0.4′/min.

Based on survey data of 156 observatories and repeat stations of China,6 observatories and 36 IGRF points outside the China in 2000 ,the geomagnetic field models of total intensity（F）, declination（D） and inclination（I） are established by Taylor polynomial model and Surface Spline model, meanwhile, the differential for Ф （latitude） and λ （longitude） of models is carried out to calculate the geomagnetic horizontal gradients, respectively. Then the gradients distribution charts of corresponding components in south-north and east-west direction are drawn, from which a comparison between horizontal gradient charts and IGRF10 for 2000 is made, consistency and difference among these three kinds of horizontal gradient are implemented, too. Finally, the spacial distribution of horizontal gradient is analyzed numerically. Results showed that horizontal gradients of while latitu of China, Ir varied F and I varied mainly with latitude, which of F ranged from 7.0 nT/min to 6.0 nT/min de increased, and got the biggest values in the central region （25°-35°N,90°-120°E） s gradients varied range from 2r/min to lt/min while latitude increased, Drs gradients both latitude and longitude, which ranged from 0.4＇/min to -0.3r/min in northsouth direction while longitude increased and -0. 1＇/min to -0.4P/min in east-west direction while latitude increased respectively.