Constraining Low-Frequency Alfvenic Turbulence in the Solar Wind Using Density Fluctuation Measurements

Abstract

One proposed mechanism for heating the solar wind, from close to the sun to beyond 10 AU, invokes low-frequency, oblique, Alfven-wave turbulence. Because small-scale oblique Alfven waves (kinetic Alfven waves) are compressive, the measured density fluctuations in the solar wind place an upper limit on the amplitude of kinetic Alfven waves and hence an upper limit on the rate at which the solar wind can be heated by low-frequency, Alfvenic turbulence. We evaluate this upper limit for both coronal holes at 5 solar radii and in the near-Earth solar wind. At both radii, the upper limit we find is consistent with models in which the solar wind is heated by low-frequency Alfvenic turbulence. At 1 AU, the upper limit on the turbulent heating rate derived from the measured density fluctuations is within a factor of 2 of the measured solar wind heating rate. Thus if low-frequency Alfvenic turbulence contributes to heating the near-Earth solar wind, kinetic Alfven waves must be one of the dominant sources of solar wind density fluctuations at frequencies of order 1 Hz. We also present a simple argument for why density fluctuation measurements do appear to rule out models in which the solar wind is heated by non-turbulent high-frequency waves ``sweeping'' through the ion-cyclotron resonance, but are compatible with heating by low-frequency Alfvenic turbulence.

8 pages, 3 figures, submitted to ApJ

References in corpus (12)

• Self-consistent Coronal Heating and Solar Wind Acceleration from Anisotropic Magnetohydrodynamic Turbulence
• Kinetic Simulations of Magnetized Turbulence in Astrophysical Plasmas
• Empirical Constraints on Proton and Electron Heating in the Fast Solar Wind
• Imbalanced Strong MHD Turbulence
• Alfven Wave Reflection and Turbulent Heating in the Solar Wind from 1 Solar Radius to 1 AU: an Analytical Treatment
• Role of cross helicity in magnetohydrodynamic turbulence
• Strong Imbalanced Turbulence
• Strong Anisotropic MHD Turbulence with Cross Helicity
• Turbulence in the sub-Alfvénic solar wind driven by reflection of low-frequency Alfvén waves
• Structure of Stationary Strong Imbalanced Turbulence
• Weakly Turbulent MHD Waves in Compressible Low-Beta Plasmas
• The Turbulent Heating Rate in Strong MHD Turbulence with Nonzero Cross Helicity

Cited by in corpus (37)

• Alfven Wave Solar Model (AWSoM): Coronal Heating
• The multi-scale nature of the solar wind
• Perpendicular Ion Heating by Low-Frequency Alfven-Wave Turbulence in the Solar Wind
• Solar Wind Turbulence and the Role of Ion Instabilities
• Recent progress in astrophysical plasma turbulence from solar wind observations
• Incorporating Kinetic Physics into a Two-Fluid Solar-Wind Model with Temperature Anisotropy and Low-Frequency Alfven-Wave Turbulence
• The Nature of Subproton Scale Turbulence in the Solar Wind
• High-resolution hybrid simulations of kinetic plasma turbulence at proton scales
• Density Fluctuation Spectrum of Solar Wind Turbulence between Ion and Electron Scales
• Alfven Wave Turbulence and Perpendicular Ion Temperatures in Coronal Holes
• Validity of the Taylor Hypothesis for Linear Kinetic Waves in the Weakly Collisional Solar Wind
• A Dynamical Model of Plasma Turbulence in the Solar Wind
• Solar wind turbulent cascade from MHD to sub-ion scales: large-size 3D hybrid particle-in-cell simulations
• Intermittency of Solar Wind Density Fluctuations From Ion to Electron Scales
• Proton, Electron, and Ion Heating in the Fast Solar Wind from Nonlinear Coupling Between Alfvenic and Fast-Mode Turbulence
• Interpreting Magnetic Variance Anisotropy Measurements in the Solar Wind
• Observational Test of Stochastic Heating in Low-$\beta$ Fast Solar Wind Streams
• Constraints on ion vs. electron heating by plasma turbulence at low beta
• Plasma Diagnostics of the Interstellar Medium with Radio Astronomy
• An Anisotropic Density Turbulence Model from the Sun to 1 au Derived From Radio Observations
• Modeling Kelvin-Helmholtz instability-driven turbulence with hybrid simulations of Alfvénic turbulence
• Amplitude of solar wind density turbulence from 10--45 $R_{\odot }$
• The Fluid-like Behavior of Kinetic Alfvén Turbulence in Space Plasma
• Modeling Solar Wind Variations over an 11-yr Cycle with Alfvén Wave Dissipation: a Parameter Study
• Magnetic helicity signature and its role in regulating magnetic energy spectra and proton temperatures in the solar wind
• Turbulent Proton Heating Rate in the Solar Wind from $5$ to $45R_{\odot }$
• Turbulent density fluctuations and proton heating rate in the solar wind from 9-20~R_{\odot}
• Sub-ion scale Compressive Turbulence in the Solar wind: MMS spacecraft potential observations
• Compressive high-frequency waves riding on an Alfvén/ion-cyclotron wave in a multi-fluid plasma
• On the ion-inertial range density power spectra in solar wind turbulence
• Exoplanet Radio Transits as a Probe for Exoplanetary Magnetic Fields -- Time-dependent MHD Simulations
• On the Conservation of Cross Helicity and Wave Action in Solar-Wind Models with Non-WKB Alfven Wave Reflection
• The effect of variations in magnetic field direction from turbulence on kinetic-scale instabilities
• Preparing for Solar and Heliospheric Science with the SKAO: An Indian Perspective
• The usefulness of Poynting's theorem in magnetic turbulence
• Threaded-Field-Lines Model for the Low Solar Corona Powered by the Alfven Wave Turbulence
• Ion-scale Turbulence and Energy Cascade Rate in the Solar Corona and Inner Heliosphere