论文标题
由空间结合和层流理想流动驱动的指数增强的磁重新连接的示例
Example of exponentially enhanced magnetic reconnection driven by a spatially-bounded and laminar ideal flow
论文作者
论文摘要
在实践和实际关注的实验室和自然等离子体中，磁场线失去可区分性的空间尺度$Δ_d$与范围内磁性重新连接的比例$ a $ a $ a $。在太阳能电晕中，血浆电阻率给出$ a/δ_d\ sim10^{12} $，这是磁性雷诺数$ r_m $。不同量表的悖论的传统分辨率是针对当前密度$ j $与重新连接场$ b_ {rec} $相关的，理想进化将集中到$ r_m $的一倍，因此$ j \ sim b_ {rec b_ {rec}/μ_0Δ_D$。第二个分辨率是理想的演变，即在各个时间点计算时，将最大值与最小分离的比率增加到了任意选择的磁场线之间的最大值与最小分离的比率。重新连接成为不可避免的，而$δ_{max}/δ_{min} \ sim r_m $。太阳能电晕的一个简单模型将用于数值说明，即时间的自然增加速率对于当前密度是线性的，但对于$δ_{max}/δ__{min} $，指数为指数。重新连接在时间尺度上发生，并且电流密度仅增强了$ \ ln（a/δ_d）$，从理想的演变时间和当前密度$ b_ {rec}/μ_0a$提高。在这两种分辨率中，一旦一个足够宽的区域（$Δ_R$）进行了重新连接，磁场将失去静态力量平衡，并在Alfvénic时间尺度上发展。 alfvénic演化本质上是理想的，但扩展了$δ_{max}/δ__{min} $很大的区域。
In laboratory and natural plasmas of practical interest, the spatial scale $Δ_d$ at which magnetic field lines lose distinguishability differs enormously from the scale $a$ of magnetic reconnection across the field lines. In the solar corona, plasma resistivity gives $a/Δ_d\sim10^{12}$, which is the magnetic Reynold number $R_m$. The traditional resolution of the paradox of disparate scales is for the current density $j$ associated with the reconnecting field $B_{rec}$ to be concentrated by a factor of $R_m$ by the ideal evolution, so $ j\sim B_{rec}/μ_0Δ_d$. A second resolution is for the ideal evolution to increase the ratio of the maximum to minimum separation between pairs of arbitrarily chosen magnetic field lines, $Δ_{max}/Δ_{min}$, when calculated at various points in time. Reconnection becomes inevitable where $Δ_{max}/Δ_{min}\sim R_m$. A simple model of the solar corona will be used for a numerical illustration that the natural rate of increase in time is linear for the current density but exponential for $Δ_{max}/Δ_{min}$. Reconnection occurs on a time scale and with a current density enhanced by only $\ln(a/Δ_d)$ from the ideal evolution time and from the current density $B_{rec}/μ_0a$. In both resolutions, once a sufficiently wide region, $Δ_r$, has undergone reconnection, the magnetic field loses static force balance and evolves on an Alfvénic time scale. The Alfvénic evolution is intrinsically ideal but expands the region in which $Δ_{max}/Δ_{min}$ is large.
