Analysis of the Time Lag Between Geomagnetic Ap Index and Solar Cycle
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摘要: 把1932-2006年地磁Ap指数12个月流动均值分解成为(Ap)R和(Ap)I.其中(Ap)R为太阳黑子数R的线性函数,与太阳黑子数R相位相同,可能对应于日冕物质抛射(CME)等地磁控制因素. (Ap)I分量与太阳黑子数R相位相差约180°,该分量可能对应于极冕洞变化(从太阳峰年开始,由日面极区逐渐向赤道延伸).以地磁Ap指数与太阳黑子数R滞后非常严重的第20太阳周为例,证实了(Ap)I分量与极冕洞向赤道延伸循环变化相对应.因此极冕洞循环变化可能是导致地磁扰动指数与太阳周循环相位不一致,出现滞后现象的一个十分重要原因.Abstract: The data of twelve-month running average of monthly mean Ap index from 1932 to 2006 is decomposed into two components, (Ap)R and (Ap)I. (Ap)R is a linear function of the twelve-month running average of monthly mean sunspot number R, which has the same phase with sunspot number R and is possible due to Coronal Mass Ejections and equatorial coronal holes. The latter is due to long lived solar wind sources such as polar coronal holes extending toward equator and is inconsistent with sunspot number R in phase. Analyzing of (Ap)I and polar coronal holes variation of cycle 20, in which the lag between twelve-month running average of monthly mean Ap index and twelve-month running average of monthly mean R is remarkable, it is testified that the (Ap)I component corresponds to polar coronal holes. Thus it is concluded that the variation of polar coronal holes is a very important factor, which contributes possibly to the lag time between Ap index and solar cycle.
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Key words:
- Sunspot number /
- Geomagnetic indices /
- Polar coronal holes
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