Journal Article

Multifractal Behavior of Energetic Neutral Atom Time Series from IBEX

Schwadron, N. A, Shrestha, B. L, Sarlis, N. V, Livadiotis, G, McComas, D. J, Rankin, J. S

2026

Overview

Energetic neutral atom (ENA) flux time series measured by the Interstellar Boundary Explorer (IBEX) from the north and south polar regions have recently revealed persistence, which is in accord with the persistence in the solar wind (SW) flow pressure at 1 au. This is not unexpected since the SW is involved in the generation of ENAs. Here, we further explore the origins of this similarity by studying for the first time the multifractal character inherent to these time series. We show that even when removing periodic trends from the time series, the remaining fluctuations exhibit rich multifractality. The multifractality reflects the existence of multiple long-range correlations in the ENA fluctuations. The north polar region presents wider multifractality than the south, exhibiting higher complexity. This is compatible with the fact that the northern region is much more affected than the southern from the IBEX Ribbon, an unanticipated ENA source discovered by IBEX. The ENA flux time series multifractal spectra (MFS) show a clear tendency (>70%) to be right-skewed. SW flow pressure MFS is also right-skewed, indicating the influence of the SW pressure on the ENAs. The analysis relies on two modern techniques commonly used in fractal analysis: the multifractal detrended fluctuation analysis (MFDFA) and the Multiscale Multifractal Analysis (MMA), which is a generalization of MFDFA, both of order m = 3 (determined in our previous study as optimal for detrending). Finally, the MMA of ENA flux time series indicates persistence in 97% of the cases studied, generalizing our previous results.

• Publisher: IOP Publishing
• Subject: Fluctuations / Fractal analysis / Neutral atoms / Solar wind / Time series