24 Oct 2023
 | 24 Oct 2023
Status: this preprint is open for discussion.

Permutation Entropy and Complexity Analysis of Large-scale Solar Wind Structures and Streams

Emilia Katja Johanna Kilpua, Simon Good, Matti Ala-Lahti, Adnane Osmane, and Venla Koikkalainen

Abstract. In this work, we perform a statistical study of magnetic field fluctuations in the solar wind at 1 au using permutation entropy and complexity analysis. Slow and fast wind, magnetic clouds, interplanetary coronal mass ejection (ICME)-driven sheath regions and slow-fast stream interaction regions (SIRs) have been investigated separately. Our key finding is that there are significant differences in permutation entropy and complexity values between the solar wind types at larger timescales and little difference at small timescales. Differences become more distinct with increasing timescale, suggesting that smaller-scale turbulent features are more universal. At larger timescales, the analysis method can be used to identify localized spatial structures. We found that fluctuation properties in compressive structures (sheaths and SIRs) exhibit a clear locality. Our results shows that, in all cases apart from magnetic clouds at largest scales, solar wind fluctuations are stochastic with the fast wind having the highest entropies and low complexities. Magnetic clouds in turn exhibit the lowest entropy and highest complexity, consistent with them being coherent structures in which the magnetic field components vary in an ordered manner. SIRs, slow wind and ICME sheaths are intermediate to magnetic clouds and fast wind, reflecting the increasingly ordered structure. Our results also indicate that permutation entropy – complexity analysis is a useful tool for characterizing the solar wind and investigating the nature of its fluctuations.

Emilia Katja Johanna Kilpua et al.

Status: open (until 30 Dec 2023)

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Emilia Katja Johanna Kilpua et al.

Emilia Katja Johanna Kilpua et al.


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Short summary
The solar wind is organised to slow and fast streams, interaction regions and transient structures originating from solar eruptions. Their internal characteristics are not well understood. The more comprehensive understanding of such features can give insight on physical processes governing their formation and evolution. Using tools from information theory we find that the solar wind shows universal turbulent properties on smaller scales while on larger-scale clear differences arise.