arXiv 1907.080622019-07physics.plasm-ph

具有零点和X点的磁重联

Magnetic reconnection with null and X-points

Allen H. Boozer

DOI：: 10.1063/1.5121320

摘要：

X点和X点本身对磁重联并不直接重要，因为可分辨的磁力线并不靠近它们。即使在无碰撞的等离子体中，在尺度$c/ω_{pe}$上彼此接近的磁场线在演化过程中变得不可区分。重要的是，穿过零点和X点附近的磁力线可以探测到不同的空间区域。传统的重联理论假设重联的磁通量必须被电场耗散或扩散。这种假设在三维系统中是错误的，因为理想的演化可以导致覆盖大体积的磁场线在不可分辨尺度$c/ω_{pe}$内彼此接近。当电子碰撞时间$τ_{ei}$短于磁场$τ_{ev}$的演化时间时，$c/ω_{pe}$的重要性由电阻时间尺度$τ_η=(η/μ_0)L^2$和系统尺度$L$代替。磁雷诺数是$R_m\equivτ_η/τ_{ev}$是巨大的，在许多重联问题的兴趣。磁通量扩散意味着重连与演化尺度竞争所需的电流密度为$R_m$，而磁通量混合意味着与演化尺度竞争所需的电流密度为$\ln R_m$。

英文摘要：

Null and X-points are not themselves directly important to magnetic reconnection because distinguishable field lines do not approach them closely. Even in a collision-free plasma, magnetic field lines that approach each other on a scale $c/ω_{pe}$ become indistinguishable during an evolution. What is important is the different regions of space that can be explored by magnetic field lines that pass in the vicinity of null and X-points. Traditional reconnection theories made the assumption that the reconnected magnetic flux must be dissipated or diffused by an electric field. This assumption is false in three dimensional systems because an ideal evolution can cause magnetic field lines that cover a large volume to approach each other within the indistinguishability scale $c/ω_{pe}$. When the electron collision time $τ_{ei}$ is short compared to the evolution time of the magnetic field $τ_{ev}$, the importance of $c/ω_{pe}$ is replaced by the resistive time scale $τ_η=(η/μ_0)L^2$ with $L$ the system scale. The magnetic Reynolds number is $R_m\equivτ_η/τ_{ev}$ is enormous in many reconnection problems of interest. Magnetic flux diffusion implies the current density required for reconnection to compete with evolution scales as $R_m$ while flux mixing implies the required current density to compete scales as $\ln R_m$.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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