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arXiv · 2607.01475

Understanding Non-Gaussian Chorus Wave Statistics via the Benjamin-Feir Index

D. J. Ratliff·O. Allanson·D. Rasinskaite·J. Stawarz·C. E. J. Watt·S. Chakraborty·A. W. Smith
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Abstract

We derive an extended wave action model for equatorial chorus waves, identifying a wave activity index (a version of the Benjamin-Feir index, BFI) which indicates non-Gaussian frequency spectra emerge when BFI$>$0.5. Global maps of this index indicate the night and dawn sectors ($0<{\rm MLT}<9)$ of the magnetosphere as the primary region for non-Gaussian wave statistics to emerge. Comparisons with events measured by the Van Allen probe A demonstrate good qualitative agreement whilst identifying key aspects for model refinement. A key strength of our model that our work highlights is its ability to account for the asymmetric frequency spectra characteristic of non-Gaussian chorus. This work ultimately establishes the first wave activity index that distinguishes Gaussian and non-Gaussian wave scenarios from first principles, providing the groundwork for a threshold-based quantification for use in space weather modelling.

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D. J. Ratliff, O. Allanson, D. Rasinskaite, J. Stawarz, C. E. J. Watt, S. Chakraborty, A. W. Smith. 2026-07-03. Understanding Non-Gaussian Chorus Wave Statistics via the Benjamin-Feir Index. https://arxiv.org/abs/2607.01475

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