The Near-Sun Streamer Belt Solar Wind: Turbulence and Solar Wind Acceleration

Abstract

The fourth orbit of Parker Solar Probe (PSP) reached heliocentric distances down to 27.9 Rs, allowing solar wind turbulence and acceleration mechanisms to be studied in situ closer to the Sun than previously possible. The turbulence properties were found to be significantly different in the inbound and outbound portions of PSP's fourth solar encounter, likely due to the proximity to the heliospheric current sheet (HCS) in the outbound period. Near the HCS, in the streamer belt wind, the turbulence was found to have lower amplitudes, higher magnetic compressibility, a steeper magnetic field spectrum (with spectral index close to -5/3 rather than -3/2), a lower Alfvénicity, and a "1/f" break at much lower frequencies. These are also features of slow wind at 1 au, suggesting the near-Sun streamer belt wind to be the prototypical slow solar wind. The transition in properties occurs at a predicted angular distance of ~4° from the HCS, suggesting ~8° as the full-width of the streamer belt wind at these distances. While the majority of the Alfvénic turbulence energy fluxes measured by PSP are consistent with those required for reflection-driven turbulence models of solar wind acceleration, the fluxes in the streamer belt are significantly lower than the model predictions, suggesting that additional mechanisms are necessary to explain the acceleration of the streamer belt solar wind.

References in corpus (24)

• Self-consistent Coronal Heating and Solar Wind Acceleration from Anisotropic Magnetohydrodynamic Turbulence
• The Evolution and Role of Solar Wind Turbulence in the Inner Heliosphere
• Recent progress in astrophysical plasma turbulence from solar wind observations
• The Solar Probe Cup on Parker Solar Probe
• First in-situ Measurements of Electron Density and Temperature from Quasi-Thermal Noise Spectroscopy with Parker Solar Probe/FIELDS
• Origins of the Ambient Solar Wind: Implications for Space Weather
• Magnetic connectivity of the ecliptic plane within 0.5 AU : PFSS modeling of the first PSP encounter
• Shear-Driven Transition to Isotropically Turbulent Solar Wind Outside the Alfven Critical Zone
• Three-dimensional simulation of the fast solar wind driven by compressible magnetohydrodynamic turbulence
• Cross Helicity Reversals In Magnetic Switchbacks
• Enhanced Energy Transfer Rate in Solar Wind Turbulence Observed near the Sun from Parker Solar Probe
• Violation of the zeroth law of turbulence in space plasmas
• On the 1/f spectrum in the solar wind and its connection with magnetic compressibility
• Tearing instability and periodic density perturbations in the slow solar wind
• Enhanced proton parallel temperature inside patches of switchbacks in the inner heliosphere
• Relating streamer flows to density and magnetic structures at the Parker Solar Probe
• The low-frequency break observed in the slow solar wind magnetic spectra
• The Radial Dependence of Proton-scale Magnetic Spectral Break in Slow Solar Wind during PSP Encounter 2
• Turbulence characteristics of switchbacks and non-switchbacks intervals observed by \emph{Parker Solar Probe}
• Applicability of Taylor's Hypothesis during Parker Solar Probe perihelia
• Measurement of the Open Magnetic Flux in the Inner Heliosphere down to 0.13AU
• A Modified Version of Taylor's Hypothesis for Solar Probe Plus Observations
• Detailed imaging of coronal rays with the Parker Solar Probe
• On the interpretation of Parker Solar Probe Turbulent Signals

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• Parker Solar Probe: Four Years of Discoveries at Solar Cycle Minimum
• Applicability of Taylor's Hypothesis during Parker Solar Probe perihelia
• Measurement of the Open Magnetic Flux in the Inner Heliosphere down to 0.13AU
• Geometry of Magnetic Fluctuations near the Sun from PSP
• Magnetic field spectral evolution in the inner heliosphere
• Statistical analysis of intermittency and its association with proton heating in the near Sun environment
• The Evolution of the 1/f Range Within a Single Fast-Solar-Wind Stream Between 17.4 and 45.7 Solar Radii
• Turbulence Properties of Interplanetary Coronal Mass Ejections in the Inner Heliosphere: Dependence on Proton Beta and Flux Rope Structure
• 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
• Nature and Scalings of Density Fluctuations of Compressible MHD Turbulence with Applications to the Solar Wind
• Multi-spacecraft Study of the Solar Wind at Solar Minimum: Dependence on Latitude and Transient Outflows
• Influence of the heliospheric current sheet on the evolution of solar wind turbulence
• Does Turbulence along the Coronal Current Sheet Drive Ion Cyclotron Waves?
• On the Turbulent Reduction of Drifts for Solar Energetic Particles
• The influence of Parker spiral on the reflection-driven turbulence