TitleOn slow solar wind with high Alfvénicity: from composition and microphysics to spectral properties
Publication TypeJournal Article
Year of Publication2018
AuthorsAmicis, R’, Matteini, L, Bruno, R
JournalMonthly Notices of the Royal Astronomical Society
Date Published3/2019
KeywordsAstrophysics - Solar and Stellar Astrophysics; methods: data analysis; parker solar probe; Physics - Data Analysis; Physics - Plasma Physics; Physics - Space Physics; Solar Probe Plus; Solar wind; Statistics and Probability; turbulence

Alfvénic fluctuations are very common features in the solar wind and are found especially within the main portion of fast-wind streams while the slow wind usually is less Alfvénic and more variable. In general, the fast and slow winds show many differences, which span from the large-scale structure to small-scale phenomena, including also a different turbulent behaviour. Recent studies, however, have shown that even the slow wind can sometimes be highly Alfvénic, with fluctuations as large as those of the fast wind. This study is devoted to presenting many facets of this Alfvénic slow solar wind, including for example the study of the source regions and their connection to coronal structures, large-scale properties, and microscale phenomena and also impact on the spectral features. This study will be conducted performing a comparative analysis with the typical slow wind and with the fast wind. It has been found that the fast wind and the Alfvénic slow wind share common characteristics, probably attributable to their similar solar origin, that is coronal-hole solar wind. Given these similarities, it is suggested that in the Alfvénic slow wind a major role is played by the superradial expansion responsible for the lower velocity. Relevant implications of these new findings for the upcoming Solar Orbiter and Solar Probe Plus missions, and more in general for turbulence measurements close to the Sun, will be discussed.


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