慢阿尔文湍流在磁开关和非磁开关区间中的正负级联率：\emph{Wind} 卫星观测
Negative and Positive Cascade Rates of Slow Alfvénic Turbulence in Switchback and Non-switchback Intervals: \emph{Wind} Observations
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- Florida Institute of Technology（佛罗里达理工学院）
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中文总结 AI 辅助
基于 Wind 卫星数据，研究发现非磁开关区间呈现正级联和 -3/2 谱标度，而磁开关区间呈现负级联和更陡的谱，表明大磁场旋转改变能量传递方向。
中文摘要 AI 辅助
我们使用基于 Politano-Pouquet 的方法估计慢太阳风中非平衡阿尔文湍流的湍流级联率，该方法不需要各向同性假设。我们分析了 \emph{Wind} 航天器提供的选定的 8 小时区间。这些区间的特征是近均匀性、弱速度剪切和非平衡阿尔文涨落，并根据磁场相对于平均场的角展度分为磁开关或非磁开关区间。磁开关区间通过大的磁场旋转来识别，而非磁开关区间仅表现出小的角度偏差。我们的结果表明，非磁开关区间表现出正的总级联率和与 $-3/2$ 标度一致的功率谱，表明存在正向能量级联。相比之下，磁开关区间的特征为负的总级联率（逆级联），以及更陡的功率谱，谱指数约为 $-1.6$。这表明大的磁场旋转可以显著改变阿尔文慢太阳风中尺度间的能量传递。结果表明，磁开关可能与额外的物理过程有关，例如局部不稳定性或与重连相关的结构，这些过程改变了湍流级联的方向和大小。这些发现可能有助于解释先前在非平衡阿尔文太阳风湍流中报告的负级联率。
英文摘要
We estimate the turbulent cascade rate in imbalanced Alfvénic turbulence in the slow solar wind using a Politano--Pouquet-based approach that does not require an isotropic assumption. We analyze selected 8-hour intervals provided by \emph{Wind} spacecraft. These intervals are characterized by near-homogeneity, weak velocity shear, and imbalanced Alfvénic fluctuations, and are classified as switchback or non-switchback depending on the angular spread of the magnetic field relative to the mean field. Switchback intervals are identified by large magnetic-field rotations, whereas non-switchback intervals exhibit only small angular deviations. Our results show that non-switchback intervals exhibit a positive total cascade rate and power spectra consistent with a $-3/2$ scaling, indicative of a forward energy cascade. In contrast, switchback intervals are characterized by a negative total cascade rate (inverse cascade), and by steeper power spectra with a spectral index of approximately $-1.6$. This indicates that large magnetic-field rotations can substantially modify the scale-to-scale energy transfer in Alfvénic slow solar wind. The results suggest that switchbacks may be associated with additional physical processes, such as local instabilities, or reconnection-related structures, that alter the direction and magnitude of the turbulent cascade. These findings may help explain previous reports of negative cascade rates in imbalanced Alfvénic solar-wind turbulence.
