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

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http://hdl.handle.net/10138/334230

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Good , S W , Kilpua , E K J , Ala-Lahti , M , Osmane , A , Bale , S D & Zhao , L -L 2020 , ' Cross Helicity of the 2018 November Magnetic Cloud Observed by the Parker Solar Probe ' , Astrophysical Journal Letters , vol. 900 , no. 2 , 32 . https://doi.org/10.3847/2041-8213/abb021

Title: Cross Helicity of the 2018 November Magnetic Cloud Observed by the Parker Solar Probe
Author: Good, S. W.; Kilpua, E. K. J.; Ala-Lahti, M.; Osmane, A.; Bale, S. D.; Zhao, L. -L.
Contributor: University of Helsinki, Particle Physics and Astrophysics
University of Helsinki, Department of Physics
University of Helsinki, Particle Physics and Astrophysics
University of Helsinki, Department of Physics
Date: 2020-09
Language: eng
Number of pages: 6
Belongs to series: Astrophysical Journal Letters
ISSN: 2041-8205
URI: http://hdl.handle.net/10138/334230
Abstract: 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's 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's 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.
Subject: Interplanetary turbulence
Solar wind
Solar coronal mass ejections
Interplanetary magnetic fields
CORONAL MASS EJECTIONS
WIND
FLUCTUATIONS
VOYAGER
EVOLUTION
HELIOS
ORIGIN
SHOCK
115 Astronomy, Space science
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