Stumpo Mirko, Consolini Giuseppe, Alberti Tommaso, Quattrociocchi Virgilio
Department of Physics, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma, Italy.
INAF-Istituto di Astrofisica e Planetologia Spaziali, via del Fosso del Cavaliere 100, 00133 Roma, Italy.
Entropy (Basel). 2020 Feb 28;22(3):276. doi: 10.3390/e22030276.
The interaction between the solar wind and the Earth's magnetosphere-ionosphere system is very complex, being essentially the result of the interplay between an external driver, the solar wind, and internal processes to the magnetosphere-ionosphere system. In this framework, modelling the Earth's magnetosphere-ionosphere response to the changes of the solar wind conditions requires a correct identification of the causality relations between the different parameters/quantities used to monitor this coupling. Nowadays, in the framework of complex dynamical systems, both linear statistical tools and Granger causality models drastically fail to detect causal relationships between time series. Conversely, information theory-based concepts can provide powerful model-free statistical quantities capable of disentangling the complex nature of the causal relationships. In this work, we discuss how to deal with the problem of measuring causal information in the solar wind-magnetosphere-ionosphere system. We show that a time delay of about 30-60 min is found between solar wind and magnetospheric and ionospheric overall dynamics as monitored by geomagnetic indices, with a great information transfer observed between the component of the interplanetary magnetic field and geomagnetic indices, while a lower transfer is found when other solar wind parameters are considered. This suggests that the best candidate for modelling the geomagnetic response to solar wind changes is the interplanetary magnetic field component B z . A discussion of the relevance of our results in the framework of Space Weather is also provided.
太阳风与地球磁层 - 电离层系统之间的相互作用非常复杂，本质上是外部驱动力（太阳风）与磁层 - 电离层系统内部过程相互作用的结果。在此框架下，模拟地球磁层 - 电离层对太阳风条件变化的响应需要正确识别用于监测这种耦合的不同参数/量之间的因果关系。如今，在复杂动力系统的框架内，线性统计工具和格兰杰因果关系模型都无法有效检测时间序列之间的因果关系。相反，基于信息论的概念可以提供强大的无模型统计量，能够理清因果关系的复杂本质。在这项工作中，我们讨论了如何处理太阳风 - 磁层 - 电离层系统中因果信息的测量问题。我们表明，通过地磁指数监测发现，太阳风与磁层和电离层的整体动力学之间存在约30 - 60分钟的时间延迟，在行星际磁场分量与地磁指数之间观察到大量的信息传递，而考虑其他太阳风参数时信息传递较低。这表明，用于模拟地磁对太阳风变化响应的最佳候选者是行星际磁场分量B z 。本文还讨论了我们的结果在空间天气框架中的相关性。
