Distribution of Negative J·E′ in the Inflow Edge of the Inner Electron Diffusion Region During Tail Magnetic Reconnection: Simulations Vs. Observations

Abstract

Magnetic reconnection is a universal phenomenon existing in the space. Energy conversion is one of the essential parts of reconnection discussed for decades. Positive energy conversion (J·E′ > 0) is usually regarded as the sign of electron diffusion region (EDR), while the negative one (J·E′ < 0) turns out to gather in the outer EDR. Here we report the negative J·E′ appearing in the inflow edge of the inner EDR, based on Magnetospheric Multiscale mission observations and particle‐in‐cell simulations. Both observations and simulations verify that this negative J·E′ is mainly contributed from the electron pressure tensor term in generalized Ohm's law. The energy loss of electrons plays the dominant effect in the electron pressure tensor, and this energy decline is caused by the electric field which is induced by the decreasing magnetic field. Our results provide significant insights to expand the understanding of the reconnection regimes.

Statistic Properties of Electron Energy Enhancement During the Inner Electron Diffusion Region Crossing

“…Based on theoretical cognition, the physical quantity $${\boldsymbol{J}}_{e}\cdot \boldsymbol{E}$$ expresses the energy volume converted from the electromagnetic field to the electrons (Figure 7a). Around the EDR, $${\boldsymbol{J}}_{e}\cdot \boldsymbol{E}$$ has a similar appearance as the term $${\boldsymbol{J}}_{e}\cdot {\boldsymbol{E}}^{\prime }$$ which has a high positive value in the inner EDR (e.g., Burch et al., 2016; Huang et al., 2021; Yi et al., 2019; Zenitani et al., 2011, 2012), and a negative value in the inflow edge (Xiong et al., 2022b) and the outer EDR (e.g., Hwang et al., 2017; Xiong et al., 2022a). Meanwhile, the change of the electron bulk energy with time is written as $$d{\varepsilon }_{\mathrm{b}\mathrm{u}\mathrm{l}\mathrm{k},e}/dt=\partial {\varepsilon }_{\mathrm{b}\mathrm{u}\mathrm{l}\mathrm{k},e}/\partial t+\nabla \cdot {\boldsymbol{K}}_{e}={\boldsymbol{J}}_{e}\cdot \boldsymbol{E}-{\boldsymbol{u}}_{e}\cdot \nabla \cdot {\boldsymbol{P}}_{e}$$, where $${\varepsilon }_{\mathrm{b}\mathrm{u}\mathrm{l}\mathrm{k},\mathrm{e}}$$ represents the electron bulk energy, $${\boldsymbol{K}}_{\mathrm{e}}$$ is the electron bulk energy flux, $${\boldsymbol{u}}_{e}$$ is the electron bulk velocity, and …”

“…We perform the full kinetic particle‐in‐cell simulation under the double Harris type current sheet configuration, which has been used in the previous study (e.g., Huang, Zhou et al., 2015; Huang et al., 2014; Xiong et al., 2022a, 2022b; Zhou et al., 2012). A zero‐guide field is applied to maintain the regularized structure of the inner EDR.…”

A Scheme of Full Kinetic Particle-in-cell Algorithms for GPU Acceleration Using CUDA Fortran Programming

“…Figure 4 displays the iteration results of magnetic reconnection obtained by CPU and GPU computing, respectively. The reconnection model is configured under double Harris current sheets with localized perturbation (e.g., Zhou et al 2012;Huang et al 2014Huang et al , 2015Xiong et al 2022aXiong et al , 2022bXiong et al , 2022c. Some basic physical parameters are listed below: the ion inertial length (d i ) is 40 grids, and the mass ratio between ions and electrons (m i /m e ) is fixed at 25; the temperature ratio between ions and electrons (T i /T e ) is 5, and the frequency ratio of electrons (ω pe /ω ce ) is 3; the simulation domain size is 800 × 1200 grids, and there are 100 pairs of ions and electrons in each cell, which means that 0.96 × 10 8 particles participate in the reconnection.…”

First-Principles Theory of the Relativistic Magnetic Reconnection Rate in Astrophysical Pair Plasmas

“…As discussed the main text, it is known that in the relativistic regime, the bulk inertia term of the Ohm's law balances the reconnection electric field E y at the edge of the diffusion region [24,26,27]. Note that the edge of the diffusion region coincides with the edge of the current sheet.…”

“…See the Appendix for the full derivation. It is known that in the relativistic regime, the bulk inertia term of Ohm's law balances the reconnection electric field E y at the edge of the diffusion region [24,26,27], as seen by comparing the blue to red curve in Fig. 2(a).…”