Journal cover Journal topic
Annales Geophysicae Sun, Earth, planets, and planetary systems An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/angeo-2018-7
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
ANGEO Communicates
23 Jan 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Annales Geophysicae (ANGEO).
Transfer entropy and cumulant based cost as measures of nonlinear causal relationships in space plasmas: applications to Dst
Jay R. Johnson1, Simon Wing2, and Enrico Camporeale3 1Andrews University, Berrien Springs, MI, USA
2The Johns Hopkins University, Applied Physics Laboratory, Laurel, Maryland, USA
3Center for Mathematics and Computer Science (CWI), Amsterdam, The Netherlands
Abstract. It is well known that the magnetospheric response to the solar wind is nonlinear. Information theoretical tools such as mutual information, transfer entropy, and cumulant based analysis are able to characterize the nonlinearities in the system. Using cumulant based cost, we show that nonlinear significance of Dst peaks at 3–12 hours lags that can be attributed to VBs which also exhibit similar behavior. However, the nonlinear significance that peaks at lags 25, 50, and 90 hours can be attributed to internal dynamics, which may be related to the relaxation of the ring current. These peaks are absent in the linear and nonlinear self-significance of VBs. Our analysis with mutual information and transfer entropy show that both methods can establish that there are a strong correlation and transfer of information from Vsw to Dst at a time scale that is consistent with that obtained from the cumulant based analysis. However, mutual information also shows that there is a strong correlation in the backward direction, from Dst to Vsw, which is counterintuitive. In contrast, transfer entropy shows that there is no or little transfer of information from Dst to Vsw, as expected because it is the solar wind that drives the magnetosphere, not the other way around. Our case study demonstrates that these information theoretical tools are quite useful for space physics studies because these tools can uncover nonlinear dynamics that cannot be seen with the traditional analyses and models that assume linear relationships.

Citation: Johnson, J. R., Wing, S., and Camporeale, E.: Transfer entropy and cumulant based cost as measures of nonlinear causal relationships in space plasmas: applications to Dst, Ann. Geophys. Discuss., https://doi.org/10.5194/angeo-2018-7, in review, 2018.
Jay R. Johnson et al.
Jay R. Johnson et al.
Jay R. Johnson et al.

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Short summary
The magnetospheric response to the solar wind is nonlinear. Information theoretical tools are able to characterize the nonlinearities in the system. We show that nonlinear significance of Dst peaks at 3–12 hours lags that can be attributed to VBs which also exhibit similar behavior. However, the nonlinear significance that peaks at lags 25, 50, and 90 hours can be attributed to internal dynamics, which may be related to the relaxation of the ring current.
The magnetospheric response to the solar wind is nonlinear. Information theoretical tools are...
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