与海洋地磁日变改正有关的长期变化和磁扰的处理
Processing of secular variation and disturbance related to marine geomagnetic diurnal variation correction
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摘要: 提出地磁日变改正中需要顾及地磁长期变化和磁扰的可靠分离,保证磁力数据改正处理具有明确的基准,提高拼接整合的精度.如果日变站能够控制测区,两者可采用时间同步固定的地磁正常场作为磁异常基准,测区的地磁长期变化由日变站实测的地磁长期变化来改正,反之,对日变站和测区应分别采用时间同步变化的地磁正常场作为磁异常基准,测区的地磁长期变化由地磁正常场的地磁长期变化来改正.为此,应该明确定义与时间相关的日变改正基值为地磁正常场与地磁异常之和.通过磁静日总场观测值偏离正常场的某种形式的长期平均值,可以逼近日变站的地磁异常.磁扰的分离应保证磁扰初动和消失相对于磁静日无磁扰的连续过渡.采用综合模型一并进行日变改正、正常场及其长期变化改正,可以更好地解决目前日变改正中遇到的问题.Abstract: Geomagnetic secular variation and short-term disturbance need to be reliably separated from the geomagnetic diurnal observation.In this wise,it will provide a definite datum for correction to geomagnetic data,and guarantee accuracy of data fusion for different cruises.In the case of good coverage of the geomagnetic diurnal observatory for marine geomagnetic survey,for the secular variation at the survey area to be corrected by that at the geomagnetic diurnal observatory,the geomagnetic normal field fixed at anuni form time would be adopted to become a datum for geomagnetic anomalies at both the geomagnetic diurnal observatory and the survey area.Otherwise,for the secular variation at the survey area to be corrected by the geomagnetic normal field,the geom agnetic normal field changing with time would be adopted to become a datum for geomagnetic anomaly at both the geomagnetic diurnal observatory and the surveyarea.Thus,the base value for geo magnetic diurnal variation correction maybe explicitly defined to be a sum of the geomagnetic normal field and geomagnetic anomaly.Geomagnetic anomaly at the diurnal observatory can be obtained to average the deviation of the geomagnetic total field obser vation from the geomag netic normal field at some way.Geomagnetic disturbance may be at tentively separated to maintain continuous transition to the disturbance beginning and end.The comprehensive model can be adopted to unitedly perform corrections for diurnal variation,normal field and its secular variation,which will preferably solve problems arisen in diurnal variation correction.
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