熵指数（EI）：一种识别行星际磁云存在的辅助工具
The Entropy Index (EI): an Auxiliary Tool to Identify the Occurrence of Interplanetary Magnetic Clouds
摘要：
通过研究与熵相关的动力学过程，建立了一种仅利用行星际磁场（IMF）数据识别行星际磁云（MC）的数学工具。作为分析方法的基础，时空熵（STE）在空间和时间域中测量图像（递归图）的“结构性”。最初，我们使用Huttunen等人2005年的数据集，研究了41个在云之前识别出冲击波的MC。分别计算了维数和时延均为1的Bx、By、Bz IMF时间序列的STE值。我们发现较高的STE值的鞘和零STE值的三个组件中的一些在大多数的MC（30 41事件）。以物理上一致的方式，选择2500个磁记录的数据窗口作为时间序列的计算间隔。由于并非所有MC同时具有零STE，因此我们创建了一个标准化索引（熵索引，称为EI）以允许连接三个分量的结果。通过使用EI，确实确定了三个未知的MC，然后MVA方法允许计算它们的边界。因此，EI建议作为一个辅助工具，以确定MC候选人只基于IMF的分析。在承诺条件下，该方法的实现为MC的自动识别过程提供了基础，并对空间天气的目的肯定是有用的。
英文摘要：
By the study of the dynamical processes related to entropy, this work aims to create a mathematical tool to identify magnetic clouds (MCs) in the interplanetary space using only interplanetary magnetic field (IMF) data. Used as basis for an analysis methodology, the spatio-temporal entropy (STE) measures the image (recurrence plots) "structuredness" in both space and time domains. Initially we worked with the Huttunen et al. 2005's dataset and studied the 41 MCs presenting a shock wave identified before the cloud. The STE values for each Bx, By, Bz IMF time series, with dimension and time delay equal to one, were respectively calculated. We found higher STE values in the sheaths and zero STE values in some of the three components in most of the MCs (30 among 41 events). In a physically consistent manner, data windows of 2500 magnetic records were selected as the calculation interval for the time series. As not all MCs have zero STE simultaneously, we created a standardization index (an entropy index, called as EI) to allow joining the result of the three components. With the use of EI three not known MCs were indeed identified and then the MVA method allowed calculating their boundaries. Thus the EI is proposed as an auxiliary tool to identify MC candidates based only on IMF analysis. In a promissor condition, this methodology implemented gives basis for an automatic MC identification procedure and surely useful for space weather purposes.
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