Three-Dimensional MHD Magnetic Reconnection Simulations With a Finite Guide Field: Proposal of the Shock-Evoking Positive-Feedback Model

Abstract

Using a three-dimensional magnetohydrodynamic model, we simulate the magnetic reconnection in a single current sheet. We assume a finite guide field, a random perturbation on the velocity field and uniform resistivity.Our model enhances the reconnection rate relative to the classical Sweet-Parker model in the same configuration. The efficiency of magnetic energy conversion is increased by interactions between the multiple tearing layers coexisting in the global current sheet. This interaction, which forms a positive-feedback system, arises from coupling of the inflow and outflow regions in different layers across the current sheet. The coupling accelerates the elementary reconnection events, thereby enhancing the global reconnection rate. The reconnection establishes flux tubes along each tearing layer. Slow-mode shocks gradually form along the outer boundaries of these tubes, further accelerating the magnetic energy conversion. Such positive-feedback system is absent in two-dimensional simulation, three-dimensional reconnection without a guide field and a reconnection under a single perturbation mode. We refer to our model as the "shock-evoking positivefeedback" model.

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.…”

Observational Evidence of Particle Acceleration Associated With Plasmoid Motions

“…The elongation of plasmoids may be due to the existence of a strong guide field (e.g. Linton & Priest 2003;Wang et al 2015). This interpretation is supported by the fact that the plasmoids were observed only in the early phase of this flare during which the free magnetic energy is expected to be stored in the form of magnetic shear near and along the polarity inversion line.…”

Three-dimensional magnetic reconnection and its application to solar flares

“…2005; Wang et al. 2007; Janvier, Kishimoto & Li 2011; Wang, Yokoyama & Isobe 2015). Finally the effect of line-tying, relevant in the context of coronal magnetic field, was investigated in Delzanno & Finn (2008), which found that the growth rate scaled with for small structure lengths (compared with the system size), while it was tearing-like for long structures.…”

“…Furthermore, multiple tearing instabilities can greatly enhance the reconnection rate in the nonlinear regime due to coupling between islands (where the reconnection outflow of a magnetic island can increase the inflow of a nearby reconnection site, e.g. Pritchett, Lee & Drake 1980;Ishii, Azumi & Kishimoto 2002;Bierwage et al 2005;Janvier, Kishimoto & Li 2011;Wang, Yokoyama & Isobe 2015). Finally the effect of line-tying, relevant in the context of coronal magnetic field, was investigated in Delzanno & Finn (2008), which found that the growth rate scaled with η for small structure lengths (compared with the system size), while it was tearing-like for long structures.…”