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arXiv · 1606.03308

Sunward-propagating Alfv\'enic fluctuations observed in the heliosphere

H. Li·C. Wang·J. W. Belcher·J. S. He·J. D. Richardson
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Abstract

The mixture/interaction of anti-sunward-propagating Alfv\'enic fluctuations (AFs) and sunward-propagating Alfv\'enic fluctuations (SAFs) is believed to result in the decrease of the Alfv\'enicity of solar wind fluctuations with increasing heliocentric distance. However, SAFs are rarely observed at 1 au and solar wind AFs are found to be generally outward. Using the measurements from Voyager 2 and Wind, we perform a statistical survey of SAFs in the heliosphere inside 6 au. We first report two SAF events observed by Voyager 2. One is in the anti-sunward magnetic sector with a strong positive correlation between the fluctuations of magnetic field and solar wind velocity. The other one is in the sunward magnetic sector with a strong negative magnetic field-velocity correlation. Statistically, the percentage of SAFs increases gradually with heliocentric distance, from about 2.7% at 1.0 au to about 8.7% at 5.5 au. These results provide new clues for understanding the generation mechanism of SAFs.

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H. Li, C. Wang, J. W. Belcher, J. S. He, J. D. Richardson. 2016-06-10. Sunward-propagating Alfv\'enic fluctuations observed in the heliosphere. https://doi.org/10.3847/2041-8205/824/1/l2

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