The origin of slow Alfvénic solar wind at solar minimum

Abstract

Although the origins of slow solar wind are unclear, there is increasing evidence that at least some of it is released in a steady state on over-expanded coronal hole magnetic field lines. This type of slow wind has similar properties to the fast solar wind, including a high degree of Alfvénicity. In this study a combination of proton, alpha particle, and electron measurements are used to investigate the kinetic properties of a single interval of slow Alfvénic wind at 0.35 AU. It is shown that this slow Alfvénic interval is characterised by high alpha particle abundances, pronounced alpha-proton differential streaming, strong proton beams, and large alpha to proton temperature ratios. These are all features observed consistently in the fast solar wind, adding evidence that at least some Alfvénic slow solar wind also originates in coronal holes. Observed differences between speed, mass flux, and electron temperature between slow Alfvénic and fast winds are explained by differing magnetic field geometry in the lower corona.

References in corpus (20)

• The chemical composition of the Sun
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• Self-consistent Coronal Heating and Solar Wind Acceleration from Anisotropic Magnetohydrodynamic Turbulence
• Coronal Holes
• Solar UV and X-Ray Spectral Diagnostics
• A comparison of Alpha Particle and Proton Beam Differential flow in Collisionally Young Solar Wind
• Forecasting Solar Wind Speeds
• Scattering of Strahl Electrons in the Solar Wind between 0.3 and 1 au: Helios Observations
• On slow solar wind with high Alfvénicity: from composition and microphysics to spectral properties
• A multiple flux-tube solar wind model
• Diagnosing solar wind origins using in-situ measurements in the inner heliosphere
• Predicting the Structure of the Solar Corona and Inner Heliosphere during Parker Solar Probe's First Perihelion Pass
• A new inner heliosphere proton parameter data set from the Helios mission
• Global solar magnetic field organization in the outer corona: influence on the solar wind speed and mass flux over the cycle
• Alpha particle thermodynamics in the inner heliosphere fast solar wind
• The Dependence of the Peak Velocity of High-Speed Solar Wind Streams as Measured in the Ecliptic by ACE and the STEREO satellites on the Area and Co-Latitude of their Solar Source Coronal Holes
• Observations of Slow Solar Wind from Equatorial Coronal Holes
• Flux-tube geometry and solar wind speed during an activity cycle
• Relationship Between Solar Wind Speed and Coronal Magnetic Field Properties
• Expansion of High Speed Solar Wind Streams from Coronal Holes through the Inner Heliosphere

Cited by in corpus (15)

• Parker Solar Probe: Four Years of Discoveries at Solar Cycle Minimum
• A solar source of Alfvénic magnetic field switchbacks: {\em in situ} remnants of magnetic funnels on supergranulation scales
• 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
• Coherent events at ion scales in the inner Heliosphere: \textit{Parker Solar Probe} observations during the first Encounter
• Observational Evidence of S-Web Source of the Slow Solar Wind
• How the area of solar coronal holes affects the properties of high-speed solar wind streams near Earth -- An analytical model
• Magnetic reconnection as a mechanism to produce multiple protonpopulations and beams locally in the solar wind
• Compositional metrics of fast and slow Alfvenic solar wind emerging from coronal holes and their boundaries
• The Contribution of Alpha Particles to the Solar Wind Angular Momentum Flux in the Inner Heliosphere
• Sensitivity of solar wind mass flux to coronal temperature
• Magnetic Field Geometry and Composition Variation in Slow Solar Winds: The Case of Sulfur
• Matching temporal signatures of solar features to their corresponding solar wind outflows
• Evolving Solar Wind Flow Properties of Magnetic Inversions Observed by Helios