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地球表面上某一点的磁场强度是随时间而变化的,而且颇为复杂。有长期变化,也有短期变化,还有突然变化。因此,掌握某点地磁场正常变化的时间分布规律,以便提供该点区域孕震异常的正常背景,是十分必要的。地磁日变化是一种以太阳日为周期的变化。可分为静日变化Sg和扰日变化Sd两种基本变化。平静变化是连续出现而叠加在基本磁场之上的,起源于电离层的一类周期性变化;干
The strength of the magnetic field at a point on the surface of the earth changes over time and is quite complex. There are long-term changes, there are short-term changes, there are sudden changes. Therefore, it is necessary to master the regular distribution of the geomagnetic field at a certain point in time to provide the normal background of the earthquake anomaly at that point. Geomagnetic diurnal variation is a change in the solar day cycle. Can be divided into static changes in Sg and daytime changes Sd two basic changes. Calm variation is a series of cyclical changes that originate in the ionosphere, occurring continuously over the basic magnetic field; dry