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首页> 外文期刊>Astronomy and astrophysics >Highly Alfvénic slow solar wind at 0.3 au during a solar minimum: Helios insights for Parker Solar Probe and Solar Orbiter
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Highly Alfvénic slow solar wind at 0.3 au during a solar minimum: Helios insights for Parker Solar Probe and Solar Orbiter

机译：在太阳能最低限度期间，高度Alfvénic慢太阳风在0.3 AU期间：帕克太阳能探头和太阳能轨道器的Helios Insights

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摘要

Alfvénic fluctuations in solar wind are an intrinsic property of fast streams, while slow intervals typically have a very low degree of Alfvénicity, with much more variable parameters. However, sometimes a slow wind can be highly Alfvénic. Here we compare three different regimes of solar wind, in terms of Alfvénic content and spectral properties, during a minimum phase of the solar activity and at 0.3 au. We show that fast and Alfvénic slow intervals share some common characteristics. This would suggest a similar solar origin, with the latter coming from over-expanded magnetic field lines, in agreement with observations at 1 au and at the maximum of the solar cycle. Due to the Alfvénic nature of the fluctuations in both fast and Alfvénic slow winds, we observe a well-defined correlation between the flow speed and the angle between magnetic field vector and radial direction. The high level of Alfvénicity is also responsible of intermittent enhancements (i.e. spikes), in plasma speed. Moreover, only for the Alfvénic intervals do we observe a break between the inertial range and large scales, on about the timescale typical of the Alfvénic fluctuations and where the magnetic fluctuations saturate, limited by the magnitude of the local magnetic field. In agreement with this, we recover a characteristic low-frequency 1/ f scaling, as expected for fluctuations that are scale-independent. This work is directly relevant for the next solar missions, Parker Solar Probe and Solar Orbiter. One of the goals of these two missions is to study the origin and evolution of slow solar wind. In particular, Parker Solar Probe will give information about the Alfvénic slow wind in the unexplored region much closer to the Sun and Solar Orbiter will allow us to connect the observed physics to the source of the plasma.
机译：太阳风中的Alfvénic波动是快速流的内在属性，而缓慢间隔通常具有非常低的Alfvénicity，具有更大的变量参数。但是，有时慢风可以很高的alfvénic。在这里，我们在太阳能活动的最小阶段和0.3 Au的最小阶段，在alfvnnic含量和光谱特性方面比较太阳风的三个不同的太阳风制度。我们表明快速和alfvénic缓慢间隔具有一些共同的特征。这将提示一种类似的太阳原子，后者来自超越磁场线，同时在1 AU和最大的太阳循环中观察。由于快速和阿法尼慢风中的波动的alfvénic性质，我们观察到磁场矢量和径向之间的流速和角度之间的明确相关性。高水平的Alfvénicity也负责等离子体速度的间歇增强（即尖峰）。此外，仅针对alfvénic间隔我们观察惯性范围和大尺度之间的突破，围绕典型的Alfvénic波动的时间尺度以及磁波动饱和，受局部磁场的大小限制。同意此，我们恢复了特征低频1 / f缩放，正如与尺度无关的波动的预期。这项工作与下一个太阳能特派团，帕克太阳能探头和太阳能轨道直接相关。这两个任务的目标之一是研究慢太阳风的起源和演变。特别是，帕克太阳能探头将提供有关未开发的地区中的alfvénic慢风的信息，更接近太阳，太阳能轨道器允许我们将观察到的物理连接到等离子体的来源。

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