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arXiv · 2604.03089

Finite Ion Temperature Effects on the Merging of Current-Carrying ELM Filaments in the edge region of a tokamak

Souvik Mondal·Nirmal Bisai·Abhijit Sen·Indranil Bandyopadhyay
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Abstract

Edge-localized-mode (ELM) filaments are crucial for cross-field transport at the tokamak edge; yet, their dynamics are often analyzed using the cold-ion approximation, despite experimental data indicating that Ti~Te . This study employs a normalized three-dimensional fluid model to investigate the influence of finite ion temperature on the dynamics of unidirectional current-carrying ELM-like filaments. We demonstrate that increasing ion temperature substantially alters filament propagation and interaction, resulting in a delay of filament merging despite an increase in total kinetic energy due to a stronger pressure-gradient drive. The examination of single-filament dynamics indicates that finite ion temperature generates asymmetric potential structures, strong poloidal flows, and persistent rotational motion, which channel kinetic energy from radial propagation into vortical dynamics. A comprehensive examination of the ion-to-electron temperature ratio reveals a distinct transition from radially dominated to rotation-dominated behavior as ion temperature increases. These results provide a unified physical explanation for reduced radial transport and delayed merging in the warm-ion domain, emphasizing the necessity of incorporating ion temperature effects in the modeling of ELM filament dynamics and edge plasma transport.

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Souvik Mondal, Nirmal Bisai, Abhijit Sen, Indranil Bandyopadhyay. 2026-04-03. Finite Ion Temperature Effects on the Merging of Current-Carrying ELM Filaments in the edge region of a tokamak. https://arxiv.org/abs/2604.03089

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