Plasmoid-mediated reconnection during nonlinear peeling-ballooning edge-localized modes

TL;DR

This paper investigates plasmoid-mediated magnetic reconnection during nonlinear Peeling-Ballooning edge-localized modes in tokamak plasmas, revealing the formation and disruption of current sheets through nonlinear resistive MHD simulations.

Contribution

It demonstrates the formation of multi-scale current sheets and their disruption during P-B ELMs, highlighting the role of plasmoid-mediated reconnection in these phenomena.

Findings

Formation of large-scale and small-scale current sheets during P-B ELMs

Current sheets break during reconnection bursts at high Lundquist numbers

Secondary growth of intermediate modes leads to relaxation of the instability

Abstract

Plasmoid-mediated reconnection is investigated for nonlinear Peeling-Ballooning Edge-Localized Modes (P-B ELMs). The formation of current sheets and the transition to 3-D current sheet instability is demonstrated through fully nonlinear resistive MHD simulations of P-B ELMs in DIII- D discharges. Large-scale axisymmetric current sheets, as well as small-scale poloidally extending current sheets, are formed as the coherent P-B ELM filaments nonlinearly evolve. It is observed that, at high Lundquist numbers, these current sheets break during a reconnection burst, i.e. a secondary exponential growth of intermediate modes followed by relaxation due to the suppression of P-B drive.