Exploring Complexity Measures for Analysis of Solar Wind Structures and Streams

Abstract

In this paper we use statistical complexity and information theory metrics to study structure within solar wind time series. We explore this using entropy-complexity and information planes, where the measure for entropy is formed using either permutation entropy or the degree distribution of a horizontal visibility graph (HVG). The entropy is then compared to the Jensen complexity (Jensen-Shannon complexity plane) and Fisher information measure (Fisher-Shannon information plane), formed both from permutations and the HVG approach. Additionally we characterise the solar wind time series by studying the properties of the HVG degree distribution. Four types of solar wind intervals have been analysed, namely fast streams, slow streams, magnetic clouds and sheath regions, all of which have distinct origins and interplanetary characteristics. Our results show that, overall, different metrics give similar results but Fisher-Shannon, which gives a more local measure of complexity, leads to a larger spread of values in the entropy-complexity plane. Magnetic cloud intervals stood out in all approaches, in particular when analysing the magnetic field magnitude. Differences between solar wind types (except for magnetic clouds) were typically more distinct for larger time lags, suggesting universality in fluctuations for small scales. The fluctuations within the solar wind time series were generally found to be stochastic, in agreement with previous studies. The use of information theory tools in the analysis of solar wind time series can help to identify structures and provide insight into their origin and formation.

Published in Nonlinear Processes in Geophysics, September 2025

References in corpus (16)

• From time series to complex networks: the visibility graph
• The multi-scale nature of the solar wind
• Coronal Holes
• The Evolution and Role of Solar Wind Turbulence in the Inner Heliosphere
• Description of stochastic and chaotic series using visibility graphs
• Full-Sun observations for identifying the source of the slow solar wind
• Distinguishing noise from chaos: objective versus subjective criteria using Horizontal Visibility Graph
• Permutation Entropy and Statistical Complexity Analysis of Turbulence in Laboratory Plasmas and the Solar Wind
• The temporal and spatial scales of density structures released in the slow solar wind during solar activity maximum
• Detection of small magnetic flux ropes from the third and fourth Parker Solar Probe encounters
• Radial Evolution of Magnetic Field Fluctuations in an Interplanetary Coronal Mass Ejection Sheath
• Recurrence based quantification of dynamical complexity in the Earth's magnetosphere at geospace storm timescales
• Nonlinear reflection process of linearly-polarized, broadband Alfvén waves in the fast solar wind
• Small-scale flux ropes in ICME sheaths
• Structure and fluctuations of a slow ICME sheath observed at 0.5 au by the Parker Solar Probe
• Flux-tube-dependent propagation of Alfvén waves in the solar corona