Kinetic-scale Current Sheets in the Solar Wind at 1 au: Scale-dependent Properties and Critical Current Density
Kinetic-scale Current Sheets in the Solar Wind at 1 au: Scale-dependent Properties and Critical Current Density
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DOI：
10.3847/2041-8213/ac4fc4
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发表时间：
2021-12
期刊：
影响因子：
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通讯作者：
I. Vasko;K. Alimov;T. Phan;S. Bale;Forrest Mozer;A. Artemyev
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作者：
I. Vasko;K. Alimov;T. Phan;S. Bale;Forrest Mozer;A. Artemyev
我们在11个样品s - 1磁场分辨率下，对Wind航天器在124天内收集的17043个质子动力学尺度电流片（CSs）进行了分析。CSs的厚度为λ，从几十公里到1000公里不等，典型值约为100公里，或在0.1-10λ p之间，以局部质子惯性长度λ p表示。我们发现，小尺度CSs的电流密度较大，j0≈6 nAm−2·(λ/100 km)−0.56，但不超过一个临界值，ja，对应于离子和电子之间的局部alv<s:1>速度漂移。观察到的趋势在归一化单位下保持不变：J0/JA≈0.17·(λ/λp)−0.51。磁剪切角与CS空间尺度相关：Δθ≈19°·（λ/λp）0.5。观测到的相关性与局部湍流是太阳风中质子动力学尺度CSs的来源一致，而限制电流密度的机制仍有待了解。
We present analysis of 17,043 proton kinetic-scale current sheets (CSs) collected over 124 days of Wind spacecraft measurements in the solar wind at 11 samples s−1 magnetic field resolution. The CSs have thickness, λ, from a few tens to one thousand kilometers with typical values around 100 km, or within about 0.1–10λ p in terms of local proton inertial length, λ p . We found that the current density is larger for smaller-scale CSs, J 0 ≈ 6 nAm−2 · (λ/100 km)−0.56, but does not statistically exceed a critical value, J A , corresponding to the drift between ions and electrons of local Alvén speed. The observed trend holds in normalized units: J0/JA≈0.17·(λ/λp)−0.51 . The CSs are statistically force-free with magnetic shear angle correlated with CS spatial scale: Δθ≈19°·(λ/λp)0.5 . The observed correlations are consistent with local turbulence being the source of proton kinetic-scale CSs in the solar wind, while the mechanisms limiting the current density remain to be understood.