Diffusion regions and 3D energy mode development in spontaneous reconnection

Abstract

The understanding of magnetic reconnection in three-dimensions (3D) is far shallower than its counterpart in two-dimensions due to its potential complication, not to mention the evolving of the spontaneously growing turbulence. We investigate the reason for reconnection acceleration on the characters and development of diffusion regions and sheared 3D energy modes (energy modes that are not parallel to the antiparallel magnetic fields) during the turbulence building stage. We found that multiple reconnection layers emerge due to the growth of 3D sheared tearing instability. Diffusion regions in adjacent reconnection layers form an inflow-outflow coupling that enhances the local reconnection. Further coupling of the existing energy modes breeds new energy modes near the current sheet edge. As reconnection layers span and interact with each other across the whole current sheet, global magnetic energy consumption accelerates. The significant contribution of 3D energy modes and their interaction to the reconnection rate enhancement seems to be independent of magnetic diffusivity. On the other hand, the global guide field changes the layout of the 3D reconnection layer and thus determines whether the system is fast-reconnection-preferable.

3D turbulent reconnection: Theory, tests, and astrophysical implications

“…While the study in Huang and Bhattacharjee (2016) support the LV99 expectation to the transfer of reconnection to the turbulent regime, some statements of these study contradict to the findings in all other numerical studies by performed by different groups around the world that also studied 3D reconnection. In particular, the statement of the similarity of 2D and 3D magnetic reconnection in Huang and Bhattacharjee (2016) is at odds with the findings by other authors who report that in 3D the reconnection is evolving differently from that in 2D (see Oishi et al, 2015;Wang, Yokoyama, and Isobe, 2015;Striani et al, 2016;Beresnyak, 2017;Kowal et al, 2017;Takamoto, 2018;Wang and Yokoyama, 2019;Kowal et al, 2019). This statement in Huang and Bhattacharjee (2016) as well as their finding that the spectral slope and anisotropy of the obtained turbulence are different from expectations of MHD turbulence theory (see §II B) contradict to the LV99 expectations.…”

Particle heating and acceleration by reconnecting and nonreconnecting current sheets

“…The reconnection generated current filaments span and interact with each other across the whole initial CS, which results in global magnetic energy consumption. The characteristic of the inflow turbulence driving the largescale CS forces the field lines to wander around inside the whole initial structure and to gradually release energy by continuously developing new reconnection sites at different positions (Matthaeus & Lamkin 1986;Lazarian & Vishniac 1999;Onofri et al 2004;Kowal et al 2009Kowal et al , 2017Oishi et al 2015;Dahlin et al 2017;Wang & Yokoyama 2019;Leake et al 2020;Agudelo Rueda et al 2021). The turbulence-driven initial largescale CS fragments and expands, filling a large-scale structure with multiple CSs of different characteristic sizes (Isliker et al 2019).…”

Magnetic reconnection in the era of exascale computing and multiscale experiments

“…In collisional MHD regimes, D ∼ L/ √ S c may be set by the current sheet thickness corresponding to S c . Interaction of kinked and wrapped flux ropes can spontaneously result in complex dynamic structures broadening the current sheet 145 and enhancing dissipation 269 . To avoid recycling information in the periodic systems, the required L 3 ≈ (B guide /B rec )L is longer if we demand Alfvén transit time based on guide field is longer in the third direction than the reconnection time.…”