地球磁场的变化大体上可分为长期变化和短期变化。长期变化如磁极移动、西向漂移,磁场强度的稳定衰减以及地史上曾多次发生过的地磁极性倒转等;短期变化又可分为扰动变化和非扰动变化。扰动变化最典型的是磁暴,非扰动变化通常比较稳定和具有一定的规律或周期性,其中规律性或周期性最明显的有太阳日变化,太阴日变化、年变化和朔望月变化。地磁场的这些变化在地表各处具有普遍性和相对稳定性,在时间上具有系统重复性和节律性,故称地磁场的节律变化。太阳日变化是指地磁场各地磁要素以太阳日(24小时)为周期的节律变化,与地表的昼夜变化具有一致 Changes in the Earth’s magnetic field can be broadly divided into long-term changes and short-term changes. Long-term changes such as magnetic pole shift, west drift, stable decay of magnetic field strength, and polarity reversal of geomagnetic polarity that have occurred many times in history have also occurred. Short-term changes can be divided into disturbance changes and non-disturbance changes. The most typical disturbance is the geomagnetic storm. The undisturbed changes are generally stable and have certain regularity or periodicity. The regularity or periodicity has the most obvious solar diurnal variation, diurnal diurnal variation, annual variation and lunar change. These changes in the geomagnetic field are universal and relatively stable throughout the earth’s surface, with systematic repeatability and rhythmicity in time, so that the rhythm of the earth’s magnetic field changes. The diurnal variation of the sun refers to the variation of rhythms of the magnetic elements in the geomagnetic field with the solar day (24 hours), which is consistent with the diurnal variation of the earth’s surface