Characterizing the Impact of Alfvén Wave Forcing in Interplanetary Space on the Distribution of near-Earth Solar Wind Speeds

Abstract

Broadly, solar wind source regions can be classified by their magnetic topology as intermittently and continuously open to the heliosphere. Early models of solar wind acceleration do not account for the fastest, non-transient solar wind speeds observed near-Earth and energy must be deposited into the solar wind after it leaves the Sun. Alfvén wave energy deposition and thermal pressure gradients are likely candidates and the relative contribution of each acceleration mechanism likely depends on the source region. Although solar wind speed is a rough proxy for solar wind source region, it cannot unambiguously identify source region topology. Using near-Sun observations of the solar wind's kinetic energy flux, we predict the expected kinetic energy flux near-Earth. This predicted kinetic energy flux corresponds to the range of solar wind speeds observed in the fast solar wind and infer that the solar wind's near-Sun kinetic energy flux is sufficient to predict the distribution of fastest, non-transient speeds observed near Earth. Applying a recently developed model of solar wind evolution in the inner heliosphere, we suggest that the acceleration required to generate this distribution of fastest, non-transient speeds is likely due to the continuous deposition of energy by Alfvén wave forcing during the solar wind's propagation through interplanetary space. We infer that the solar wind's Alfvénicity can statistically map near-Earth observations to their source regions because the Alfvén wave forcing that the solar wind experiences in transit is a consequence of the source region topology.

References in corpus (22)

• The Solar Orbiter mission -- Science overview
• Magnetic Reconnection as the Driver of the Solar Wind
• Parker Solar Probe observations of proton beams simultaneous with ion-scale waves
• Interchange reconnection as the source of the fast solar wind within coronal holes
• Stellar Winds on the Main-Sequence I: Wind Model
• In situ observations of large amplitude Alfvén waves heating and accelerating the solar wind
• A zone of preferential ion heating extends tens of solar radii from Sun
• Inferred Linear Stability of Parker Solar Probe Observations using One- and Two-Component Proton Distributions
• Strong perpendicular velocity-space in proton beams observed by Parker Solar Probe
• Evolution of switchbacks in the inner Heliosphere
• The Radial Evolution of the Solar Wind as Organized by Electron Distribution Parameters
• Statistical Analysis of the Radial Evolution of the Solar Winds between 0.1 and 1 au, and their Semi-empirical Iso-poly Fluid Modeling
• Coronal sources and in situ properties of the solar winds sampled by ACE during 1999-2008
• Acceleration of polytropic solar wind: Parker Solar Probe observation and one-dimensional model
• Charge States and FIP Bias of the Solar Wind from Coronal Holes, Active Regions, and Quiet Sun
• Quantifying the Energy Budget in the Solar Wind from 13.3-100 Solar Radii
• Solar wind energy flux observations in the inner heliosphere: First results from Parker Solar Probe
• Observational Evidence of S-Web Source of the Slow Solar Wind
• Compositional metrics of fast and slow Alfvenic solar wind emerging from coronal holes and their boundaries
• Cross Helicity and the Helium Abundance as an in situ Metric of Solar Wind Acceleration
• How Alfvén waves energize the solar wind: heat vs work
• On the transition from Slow to Fast Wind as Observed in Composition Observations

Cited by in corpus (2)

• The Evolution of Heavy Ion Abundances with Solar Activity
• On the Regulation of the Solar Wind Helium Abundance by the Hydrogen Compressibility