论文标题
随机重新连接的功率和空间复杂性
Power and spatial complexity in stochastic reconnection
论文作者
论文摘要
与给定向量字段相关的空间复杂性水平可以通过简单的，依赖时间依赖的函数$ s（t）= {1 \ off 2}（1- \ hat {\ bf f} {\ bf f} _ p f} {\ bf f f}} {\ bf f fiffalse $ {\ false $ {\ bf f（x}，t），t），t）$量化。 $ {\ bf f} _l $（$ {\ bf f} _l $）是比例尺$ l $（$ l> l $）的平均字段，而单位向量为$ \ hat {\ bf f} = {\ bf f} = {\ bf f}/| {\ bf f}/| {\ bf f}因此，\ fi可以通过时间的简单，比例依赖性函数来量化； $ 0 \ leq s（t）\ leq 1 $。以前的工作调用了与速度和磁场有关的动力学和磁复杂性，$ {\ bf u（x}，t），t）$和$ {\ bf b（x}，t），$，研究磁性重新连接和扩散的湍流和磁性磁力。在本文中，使用粗粒的动量方程式，我们认为在湍流惯性范围内与磁重新连接事件相关的流体喷气机主要由lorentz force $ {\ bf {n}} _ l =（ {\ bf b} _l $。该力是由子量表电流诱导的，类似于湍流电动力$ {\ cal e} _l =（{{\ bf u \ times b}）_ l - {\ bf u} _l} _l \ times {\ bf times {\ bf bf bf b} _l in in Dynamo in Dynamo PheoRERIEN中。通常，重新连接期间高（低）磁复杂性意味着磁场的大（小）空间梯度，即强（弱）lorentz力$ {\ bf n} _l $。重新连接发射流体的喷射，因此动力学复杂性的变化速率预计与Lorentz Force $ {\ bf n} _l $注入的功率密切相关。我们使用不可压缩的，均匀的磁流失动力（MHD）模拟测试了这一预测，并将其与先前的结果相关联。因此，湍流越强（较弱），磁场越少（较小）磁场，重新连接场越强（较弱），从而越来越强。
The level of spatial complexity associated with a given vector field on an arbitrary range of scales \iffalse ${\bf F(x}, t)$ can be quantified by a simple, time-dependent function $S(t)={1\over 2}(1-\hat{\bf F}_l.\hat{\bf F}_L)_{rms}$ with ${\bf F}_l$ (${\bf F}_L$) being the average field in a volume of scale $l$ ($L>l$) and the unit vector defined as $\hat{\bf F}={\bf F}/|{\bf F}|$. Thus,\fi can be quantified by a simple, scale-dependent function of time; $0\leq S(t)\leq 1$. Previous work has invoked kinetic and magnetic complexities, associated with velocity and magnetic fields ${\bf u(x}, t)$ and ${\bf B(x}, t)$, to study magnetic reconnection and diffusion in turbulent and magnetized fluids. In this paper, using the coarse-grained momentum equation, we argue that the fluid jets associated with magnetic reconnection events at an arbitrary scale $l$ in the turbulence inertial range are predominantly driven by the Lorentz force ${\bf{N}}_l=({\bf j\times B})_l-{\bf j}_l\times {\bf B}_l$. This force, is induced by the subscale currents and is analogous to the turbulent electromotive force ${\cal E}_l=({\bf u\times B})_l-{\bf u}_l\times {\bf B}_l$ in dynamo theories. Typically, high (low) magnetic complexities during reconnection imply large (small) spatial gradients for the magnetic field, i.e., strong (weak) Lorentz forces ${\bf N}_l$. Reconnection launches jets of fluid, hence the rate of change of kinetic complexity is expected to strongly correlate with the power injected by the Lorentz force ${\bf N}_l$. We test this prediction using an incompressible, homogeneous magnetohydrodynamic (MHD) simulation and associate it with previous results. It follows that the stronger (weaker) the turbulence, the more (less) complex the magnetic field and the stronger (weaker) the reconnection field and thus the ensuing reconnection.
