On slow solar wind with high Alfvénicity: from composition and microphysics to spectral properties

Abstract

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, fast and slow wind 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 slow wind can be sometimes highly Alfvénic with fluctuations as large as those of the fast wind. The present study is devoted to present 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 micro-scale 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, i.e. coronal-hole solar wind. Given these similarities, it is suggested that in the Alfvénic slow wind a major role is played by the super-radial 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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Cited by in corpus (29)

• The multi-scale nature of the solar wind
• Magnetic Reconnection as the Driver of the Solar Wind
• Enhanced Energy Transfer Rate in Solar Wind Turbulence Observed near the Sun from Parker Solar Probe
• Enhanced proton parallel temperature inside patches of switchbacks in the inner heliosphere
• Kinetic Scale Slow Solar Wind Turbulence in the Inner Heliosphere: Co-existence of Kinetic Alfvén Waves and Alfvén Ion Cyclotron Waves
• Small-scale Flux Emergence, Coronal Hole Heating, and Flux-tube Expansion: A Hybrid Solar Wind Model
• The origin of slow Alfvénic solar wind at solar minimum
• Coherent events at ion scales in the inner Heliosphere: \textit{Parker Solar Probe} observations during the first Encounter
• Observations of Slow Solar Wind from Equatorial Coronal Holes
• Observational Evidence of S-Web Source of the Slow Solar Wind
• Energy Supply for Heating the Slow Solar Wind Observed by Parker Solar Probe between 0.17 and 0.7 au
• Modeling of Joint Parker Solar Probe - Metis/Solar Orbiter Observations
• Parker Solar Probe Observations of High Plasma Beta Solar Wind from Streamer Belt
• Compositional metrics of fast and slow Alfvenic solar wind emerging from coronal holes and their boundaries
• Dependence of Solar Wind Proton Temperature on the Polarisation Properties of Alfvénic Fluctuations at Ion-kinetic Scales
• Effects of alpha-proton differential flow on proton temperature anisotropy instabilities in the solar wind: Wind observations
• The S-Web Origin of Composition Enhancement in the Slow-to-Moderate Speed Solar Wind
• Three-dimensional local anisotropy of velocity fluctuations in the solar wind
• Inverse cascade and magnetic vortices in kinetic Alfvén-wave turbulence
• Cross Helicity and the Helium Abundance as an in situ Metric of Solar Wind Acceleration
• The Temperature Anisotropy and Helium Abundance Features of Alfvénic Slow Solar Wind Observed by Parker Solar Probe, Helios, and Wind Missions
• Sensitivity of solar wind mass flux to coronal temperature
• Slow Solar Wind Connection Science during Solar Orbiter's First Close Perihelion Passage
• Modeling imbalanced collisionless Alfvén wave turbulence with nonlinear diffusion equations
• Magnetic Field Geometry and Composition Variation in Slow Solar Winds: The Case of Sulfur
• Solar Polar Flux Redistribution based on Observed Coronal Holes
• Characterizing the Impact of Alfvén Wave Forcing in Interplanetary Space on the Distribution of near-Earth Solar Wind Speeds
• Evolution of MHD turbulence in the expanding solar wind: residual energy and intermittency
• On the Regulation of the Solar Wind Helium Abundance by the Hydrogen Compressibility