The Evolution and Role of Solar Wind Turbulence in the Inner Heliosphere
The Evolution and Role of Solar Wind Turbulence in the Inner Heliosphere
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DOI：
10.3847/1538-4365/ab60a3
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发表时间：
2020-02-01
影响因子：
8.7
通讯作者：
Whittlesey, P.
中科院分区：
文献类型：
--
作者：
Chen, C. H. K.;Bale, S. D.;Whittlesey, P.
帕克太阳探测器航天器的前两个轨道使太阳风的第一次现场测量下降到0.17 Au（或36 R圆点）的日心距离。在这里，我们提出了一个分析这些数据，研究太阳风湍流在0.17 Au和它的演变到1 Au。虽然许多功能保持相似，关键的区别在0.17 Au包括增加湍流能级超过一个数量级，磁场谱指数-3/2匹配的速度和两个Elsasser场，较低的磁压缩性与较小的慢模动能分数一致，和一个小得多的外部规模，有时间进行大量的非线性处理。向外传播的阿尔芬波动的主导地位相比，向内传播的整体增加，向内分量的径向变化是一致的，其产生的反射从大尺度梯度阿尔芬速度。在0.17 Au的湍流中的能流被发现是相似的10%，在散装太阳风动能，成为类似的40%时，外推到阿尔芬点，这对太阳通量的增加的分数和速率是一致的，其中太阳风是由这个通量驱动的模型。
The first two orbits of the Parker Solar Probe spacecraft have enabled the first in situ measurements of the solar wind down to a heliocentric distance of 0.17 au (or 36 R-circle dot). Here, we present an analysis of this data to study solar wind turbulence at 0.17 au and its evolution out to 1 au. While many features remain similar, key differences at 0.17 au include increased turbulence energy levels by more than an order of magnitude, a magnetic field spectral index of -3/2 matching that of the velocity and both Elsasser fields, a lower magnetic compressibility consistent with a smaller slow-mode kinetic energy fraction, and a much smaller outer scale that has had time for substantial nonlinear processing. There is also an overall increase in the dominance of outward-propagating Alfvenic fluctuations compared to inward-propagating ones, and the radial variation of the inward component is consistent with its generation by reflection from the large-scale gradient in Alfven speed. The energy flux in this turbulence at 0.17 au was found to be similar to 10% of that in the bulk solar wind kinetic energy, becoming similar to 40% when extrapolated to the Alfven point, and both the fraction and rate of increase of this flux toward the Sun are consistent with turbulence-driven models in which the solar wind is powered by this flux.