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arXiv · 2611.05880

The kinematic Kelvin-Helmholtz instability-driven dynamo: implications for merging compact objects

James R. Beattie·Amitava Bhattacharjee·Elias R. Most·Bart Ripperda·Alexander Philippov·Ralf S. Klessen·Salvatore Cielo
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Abstract

Binary neutron star (BNS) mergers excite a Kelvin--Helmholtz instability (KHI) in the shear layer between them. It is parasitized upon by the magnetic field to form a powerful magnetic dynamo. Using a large ensemble of high-resolution visco-resistive KHI-driven dynamo simulations we construct analytical, asymptotic in Reynolds number ($\rm{Re}$) models for the magnetic field growth rates and mean vertical field dynamo onset times. Our models suggest that in the $\rm{Re} \gg 1$ limit, the mean vertical field is seeded immediately, kinematic growth rates become asymptotic in $\rm{Re}$, and the dynamo moves out of the kinematic stage on $\mathcal{O}(0.1\,\rm{ms})$ timescales, readily attaining magnetar-strength fields during this transition. This suggests that most global BNS merger simulations are not time-resolving the correct KHI-driven dynamo regime.

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James R. Beattie, Amitava Bhattacharjee, Elias R. Most, Bart Ripperda, Alexander Philippov, Ralf S. Klessen, Salvatore Cielo. 2026-11-04. The kinematic Kelvin-Helmholtz instability-driven dynamo: implications for merging compact objects. https://arxiv.org/abs/2611.05880

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