Cross Helicity of the 2018 November Magnetic Cloud Observed by the Parker Solar Probe

Author
Keywords
Abstract
<p>Magnetic clouds are large-scale transient structures in the solar wind with low plasma-beta, low-amplitude magnetic field fluctuations, and twisted field lines with both ends often connected to the Sun. Their inertial-range turbulent properties have not been examined in detail. In this Letter, we analyze the normalized cross helicity, sigma(c), and residual energy, sigma(r), of plasma fluctuations in the 2018 November magnetic cloud observed at 0.25.au by the Parker Solar Probe. A low value of |sigma(c)| was present in the cloud core, indicating that wave power parallel and antiparallel to the mean field was approximately balanced, while the cloud\textquoterights outer layers displayed larger amplitude Alfvenic fluctuations with high |sigma(c)| values and sigma(r) similar to 0. These properties are discussed in terms of the cloud\textquoterights solar connectivity and local interaction with the solar wind. We suggest that low |sigma(c)| is likely a common feature of magnetic clouds given their typically closed field structure. Antisunward fluctuations propagating immediately upstream of the cloud had strongly negative sigma(r) values.</p>
Year of Publication
2020
Journal
The Astrophysical Journal
Volume
900
Number
Number of Pages
L32
Date Published
09/2020
URL
https://iopscience.iop.org/article/10.3847/2041-8213/abb021https://iopscience.iop.org/article/10.3847/2041-8213/abb021/pdf
DOI
10.3847/2041-8213/abb021