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arXiv 2202.12341astro-ph.SRphysics.plasm-ph
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近太阳太阳风中动力学尺度电流片：特性、尺度依赖特征和重联开始

Kinetic-scale current sheets in near-Sun solar wind: properties, scale-dependent features and reconnection onset

A. Lotekar, I. Y. Vasko, T. Phan, S. D. Bale, T. A. Bowen, J. Halekas, A. V. Artemyev, Yu. Khotyaintsev, F. S. Mozer

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摘要：

本文统计分析了帕克太阳探测器在第一近日点附近10天内观测到的11,200个质子动力学尺度电流片。CS厚度$λ$在几到200 km之间，典型值在30 km左右，电流密度在0.1到10 $μ{\rm A/m^2}$之间，典型值在0.7 $μ{\rm A/m^2}$左右。这些CS是解决由于磁场测量在73- 290样本/秒的分辨率。就质子惯性长度$λ_{p}$而言，CS厚度$λ$在约$0.1$至$10λ_{p}$的范围内，典型值约为2 $λ_{p}$。磁场大小在CS上基本上不变化，因此，电流密度由磁场对准分量主导。CS通常是不对称的，在CS边界处具有统计上不同的磁场幅度。对于较小规模的CS，电流密度较大，$J_0\approx 0.15 \cdot (λ/100\;{\rm km})^{-0.76}$ $μ{\rm A/m^2}$，但在统计上不超过与局部阿尔文速度的离子-电子漂移相对应的阿尔文电流密度$J_A$。CS具有显著的尺度依赖性电流密度和磁剪切角，$J_0/J_{A}\approx 0.17\cdot (λ/λ_{p})^{-0.67}$和$Δθ\approx 21^{\circ}\cdot (λ/λ_{p})^{0.32}$。基于这些观察和比较最近的研究在1 AU，我们得出结论，质子动力学尺度的CS在近太阳太阳风产生的湍流级联，他们是自动的参数范围内，重联是不抑制的抗磁机制，由于其几何形状所决定的湍流级联。

英文摘要：

We present statistical analysis of 11,200 proton kinetic-scale current sheets (CS) observed by Parker Solar Probe during 10 days around the first perihelion. The CS thickness $λ$ is in the range from a few to 200 km with the typical value around 30 km, while current densities are in the range from 0.1 to 10\;$μ{\rm A/m^2}$ with the typical value around 0.7\;$μ{\rm A/m^2}$. These CSs are resolved thanks to magnetic field measurements at 73--290 Samples/s resolution. In terms of proton inertial length $λ_{p}$, the CS thickness $λ$ is in the range from about $0.1$ to $10λ_{p}$ with the typical value around 2$λ_{p}$. The magnetic field magnitude does not substantially vary across the CSs and, accordingly, the current density is dominated by the magnetic field-aligned component. The CSs are typically asymmetric with statistically different magnetic field magnitudes at the CS boundaries. The current density is larger for smaller-scale CSs, $J_0\approx 0.15 \cdot (λ/100\;{\rm km})^{-0.76}$ $μ{\rm A/m^2}$, but does not statistically exceed the Alfvén current density $J_A$ corresponding to the ion-electron drift of local Alfvén speed. The CSs exhibit remarkable scale-dependent current density and magnetic shear angles, $J_0/J_{A}\approx 0.17\cdot (λ/λ_{p})^{-0.67}$ and $Δθ\approx 21^{\circ}\cdot (λ/λ_{p})^{0.32}$. Based on these observations and comparison to recent studies at 1 AU, we conclude that proton kinetic-scale CSs in the near-Sun solar wind are produced by turbulence cascade and they are automatically in the parameter range, where reconnection is not suppressed by the diamagnetic mechanism, due to their geometry dictated by turbulence cascade.

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