Line-Tied Flux Rope Relaxation and Reconnection: A 3D Kinetic Case Study

TL;DR

This study uses a novel 3D kinetic model to simulate line-tied flux rope interactions, revealing a current-dependent transition in magnetic regimes and consistent reconnection diagnostics.

Contribution

Introduces a new parallel-kinetic-perpendicular-moment (PKPM) model for simulating 3D flux rope interactions with realistic plasma parameters, capturing kinetic physics.

Findings

Ropes transition from diamagnetic to paramagnetic regimes based on current.

Kinetic dynamics are similar across different magnetic regimes.

Squashing factor and quasi-potential effectively diagnose 3D reconnection.

Abstract

Magnetic flux ropes are ubiquitous magnetic structures found in plasmas ranging from astrophysical to laboratory. We employ a newly-developed parallel-kinetic-perpendicular-moment (PKPM) model to simulate the 3D interaction and evolution of two line-tied flux ropes at realistic laboratory plasma parameters, while retaining essential parallel kinetic physics in the system. We find that ropes undergo a current-dependent transition from a diamagnetic to paramagnetic regime, which we quantify with a simple analytic model. Although the macroscopic structural evolution qualitatively differs significantly between these regimes, analyzing the reconnection in proper field-aligned coordinates reveals that the underlying kinetic dynamics remain similar. Using the squashing factor and quasi-potential as diagnostics of 3D magnetic reconnection, we identify the formation of a quasi-separatrix layer and show that these quantities provide consistent metrics for reconnection rate and structure.