北京地区地磁场Sq强度的季节变化和长期变化

本文利用北京地区的北京台（BJI）和北京十三陵台（BMT）的地磁场X、Y和Z分量时均值数据，研究了1960年至2013年期间该地区地磁场Sq强度的季节变化和长期变化.结果表明：（1）BJI台和BMT台的地磁场Sq不仅变幅相近，而且具有一致的地方时变化、季节变化、太阳活动周变化和长期变化.（2）BJI台和BMT台Sq强度的逐月变化，其中A_Sq（X）主要表现为春秋增强而冬夏减弱的季节变化.A_Sq（Y）呈现出夏季增强的半年变化.A_Sq（Z）变化较为复杂.虽然在5月和9月出现减小，但是总体来看，其变化曲线也具有夏季增强的半年变化特征.同时，Sq强度与太阳活动F₁₀₇指数之间存在明显的正相关关系，具有一致的11年太阳活动周变化和长期变化，反映出了Sq与太阳活动之间的密切关系.（3）BJI台和BMT台Sq强度差值dA_Sq表明，在大多数年份，两个台站的Sq强度之差一般不超过±2 nT，同时没有明显的季节或年周期变化特征.在2000年和2001年太阳活动高年，dA_Sq出现显著增强，最大可达12.3 nT.反映出了北京地区Sq场强度梯度的剧烈扰动与太阳活动之间的密切关系，意味着在太阳活动高年，Sq电离层发电机电流的局部结构可能发生了明显的改变.

The seasonal variation and secular variation of Sq in Beijing

Using the hourly data of the X, Y and Z component of geomagnetic field during 1960 to 2013 from Beijing and Beijing Ming Tombs geomagnetic observatories in China, the seasonal variation and secular variation of Sq's amplitude are investigated. The result shows that, (1) both in BJI and BMT observatories, there is not only almost same strength of the Sq's amplitude, but also similarly stable local time variation, seasonal variation, solar cycle variation and secular variation; (2) the amplitude of Sq (X) presents a remarkable seasonal variation with an enhancement in spring and autumn months, but Sq (Y) and Sq (Z) has an annual variation with an increasing in summer months; and there is a positive relationship between the Sq's amplitude and F₁₀₇ index, both showing a similar synchronous 11-year solar cycle variation and secular variation; (3) the difference of Sq's amplitude between BJI and BMT observatories is not greater than ±2nT in most years; but in high solar activity years, the difference shows a remarkable enhancement, suggesting the close relationship between the solar activity and the gradient of the Sq's amplitude.