海洋磁测日变校正的纬度改正方法研究

Study on latitude correction method of diurnal variation correction for marine magnetic survey

目前,在远海开阔性海域磁测中,尚难以有效设立日变站,致使日变改正仍存在着困难.本文利用地磁台站实测资料对地磁日变的纬度分布特征进行研究,发现日变值随纬度变化具有由Sq电流中心向南北两侧递增的规律,且二者之间的关系可用二次函数近似描述。以此规律为基础我们建立了纬度改正方法,该方法以经度链为基站,利用基站数据得到日变值与磁纬度的拟合函数以进行纬度改正,再调整时差作为经度校正即得到计算站的日变值.实测数据计算结果表明,相较于加权平均法,此方法在远距离(经度差达40°)仍能保持较高的校正精度(<4 nT),因而能更好地适用于远海磁测.

Nowadays,as it is difficult to effectively establish a station for measuring diurnal variation of geomagnetic field,the diurnal variation correction in the remote marine magnetic survey is greatly limited.Based on extensive researches on the latitude distribution of geomagnetic diurnal variation using data collected from geomagnetic observatories,we find that the diurnal variation value is associated with the geomagnetic latitude,and the relationship there between can be approximately fitted by a quadratic function.Specifically,the value of diurnal variation increases from the Sq current center to the north and south sides.Based on the pattern,a latitude correction method is thus established.In this method,observatories similar in longitude and varying in latitude are selected as base stations,from which the data are used to obtain relationship between the diurnal variation value and geomagnetic latitude for latitude correction.Then time difference is adjusted for longitude correction,thus obtaining diurnal variation values from various stations.Compared to the existing weighted average method,this method can still maintain a high correction accuracy(<4 nT)for remote stations(with a longitude difference of 40°),so it is more suitable for the magnetic survey in remote sea.