3D Kinetic Simulations of Driven Reconnection in Merging Force-free Flux Tubes: Drift-kink Dynamics and Particle Acceleration

We present 2D and 3D particle-in-cell simulations of driven collisionless reconnection triggered by the compression and merging of two force-free flux tubes in a strongly magnetized pair plasma. During current-sheet formation, the evolution remains quasi-2D. Reconnection onset is systematically delayed in 3D, especially for stronger guide fields. Increasing the imposed drive accelerates both tearing and drift-kink growth, while the guide field suppresses coherent drift-kink activity. All runs enter a fast-merging phase with normalized reconnection rates of order 0.08–0.1. The 3D runs show slightly stronger in-plane magnetic-energy depletion and particle energization than their 2D counterparts, indicating a modestly enhanced conversion of reconnecting magnetic energy into particle energy. Faster driving increases the fraction of particles at injection and the nonthermal energy fraction, while a stronger guide field decreases it. In contrast, the spectral slopes of the energy distributions remain similar, p ≃ 1.6–2.0, and the cutoff converges to γ cut / σ in ≃ 50 with only a weak dependence on dimensionality, drive strength, or guide field.