SEMIANNUAL VARIATION OF GEOMAGNETIC ACTIVITY
SEMIANNUAL VARIATION OF GEOMAGNETIC ACTIVITY
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DOI：
10.1029/ja078i001p00092
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发表时间：
1973-01-01
影响因子：
--
通讯作者：
MCPHERRON, RL
中科院分区：
文献类型：
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作者：
RUSSELL, CT;MCPHERRON, RL
地磁活动的半年变化在地磁数据中已得到充分证实，但其解释仍然难以捉摸。简而言之，我们认为这是由行星际场有效向南分量的半年变化引起的。南向场的产生是因为行星际场在太阳赤道坐标系中是有序的，而与磁层的相互作用是由磁层系统控制的。研究了利用行星际场向南部分的这种有效调制的几个简单模型。其中之一密切预测了观察到的半年变化的相位和幅度。该模型假设向北的行星际场是非相互作用的，并且与向南的行星际场的相互作用在太阳磁层坐标中是有序的。然而，该模型对磁层顶相互作用强度的日变化的预测与地面数据得出的地磁活动的日变化并不匹配。然而，地面数据研究证实了地磁活动对行星际磁场极性的依赖性以及地磁活动 22 年周期的预测。看来控制地磁活动半年变化的机制已经确定，但定量模型必须等待我们对太阳风-磁层耦合的了解的进一步完善。
The semiannual variation in geomagnetic activity is well established in geomagnetic data Its explanation has remained elusive, however. We propose, simply, that it is caused by a semiannual variation in the effective southward component of the interplanetary field. The southward field arises because the interplanetary field is ordered in the solar equatorial coordinate system, whereas the interaction with the magnetosphere is controlled by a magnetospheric system. Several simple models utilizing this effective modulation of the southward, component of the interplanetary field are examined. One of these closely predicts the observed phase and amplitude of the semiannual variation. This model assumes that northward interplanetary fields are noninteracting and that the interaction with southward fields is ordered in solar magnetospheric coordinates. The prediction of the diurnal variation of the strength of the interaction at the magnetopause by this model, does not, however, match the diurnal variation of geomagnetic activity as derived from ground‐based data. However, predictions of the dependence of geomagnetic activity on the polarity of the interplanetary magnetic field and of a 22‐year cycle in geomagnetic activity are confirmed by studies of ground‐based data. It appears that the mechanism controlling the semiannual variation of geomagnetic activity has been identified but that a quantitative model must await further refinements in our knowledge of the solar wind‐magnetosphere coupling.