Parallel-propagating Fluctuations at Proton-kinetic Scales in the Solar Wind are Dominated by Kinetic Instabilities

Abstract

We use magnetic helicity to characterise solar wind fluctuations at proton-kinetic scales from Wind observations. For the first time, we separate the contributions to helicity from fluctuations propagating at angles quasi-parallel and oblique to the local mean magnetic field, ${\mathbf{B}}_0$. We find that the helicity of quasi-parallel fluctuations is consistent with Alfvén-ion cyclotron and fast magnetosonic-whistler modes driven by proton temperature anisotropy instabilities and the presence of a relative drift between $\alpha$-particles and protons. We also find that the helicity of oblique fluctuations has little dependence on proton temperature anisotropy and is consistent with fluctuations from the anisotropic turbulent cascade. Our results show that parallel-propagating fluctuations at proton-kinetic scales in the solar wind are dominated by proton temperature anisotropy instabilities and not the turbulent cascade. We also provide evidence that the behaviour of fluctuations at these scales is independent of the origin and macroscopic properties of the solar wind.

arXiv commentAccepted for publication in ApJL. 6 Pages, 3 figures, 1 table

References in corpus (26)

• Measurement of the electric fluctuation spectrum of magnetohydrodynamic turbulence
• Magnetic fluctuation power near proton temperature anisotropy instability thresholds in the solar wind
• Anisotropic scaling of magnetohydrodynamic turbulence
• Kinetic Simulations of Magnetized Turbulence in Astrophysical Plasmas
• Solar Wind Turbulence and the Role of Ion Instabilities
• Recent progress in astrophysical plasma turbulence from solar wind observations
• Anisotropy of Solar Wind Turbulence between Ion and Electron Scales
• Power and spectral index anisotropy of the entire inertial range of turbulence in the fast solar wind
• Evidence for Electron Landau Damping in Space Plasma Turbulence
• Anisotropy of Alfvénic Turbulence in the Solar Wind and Numerical Simulations
• Three-Dimensional Structure of Solar Wind Turbulence
• The Role of Proton-Cyclotron Resonance as a Dissipation Mechanism in Solar Wind Turbulence: A Statistical Study at Ion-Kinetic Scales
• Predicted Impacts of Proton Temperature Anisotropy on Solar Wind Turbulence
• A comparison of Alpha Particle and Proton Beam Differential flow in Collisionally Young Solar Wind
• Instabilities Driven by the Drift and Temperature Anisotropy of Alpha Particles in the Solar Wind
• On the Interpretation of Magnetic Helicity Signatures in the Dissipation Range of Solar Wind Turbulence
• A zone of preferential ion heating extends tens of solar radii from Sun
• A Majority of Solar Wind Intervals Support Ion-Driven Instabilities
• Spectral Features of Magnetic Fluctuations at Proton Scales from Fast to Slow Solar Wind
• Physical Interpretation of the Angle Dependent Magnetic Helicity Spectrum in the Solar Wind: The Nature of Turbulent Fluctuations near the Proton Gyroradius Scale
• Diagnosing solar wind origins using in-situ measurements in the inner heliosphere
• Limits on Alpha Particle Temperature Anisotropy and Differential Flow from Kinetic Instabilities: Solar Wind Observations
• Collisional Thermalization of Hydrogen and Helium in Solar Wind Plasma
• Power Anisotropy in the Magnetic Field Power Spectral Tensor of Solar Wind Turbulence
• Anisotropies of the magnetic field fluctuations at kinetic scales in the solar wind : Cluster observations
• Linking Fluid and Kinetic Scales in Solar Wind Turbulence

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• Kinetic Scale Slow Solar Wind Turbulence in the Inner Heliosphere: Co-existence of Kinetic Alfvén Waves and Alfvén Ion Cyclotron Waves
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• Ion-Driven Instabilities in the Inner Heliosphere I: Statistical Trends
• Dependence of Solar Wind Proton Temperature on the Polarisation Properties of Alfvénic Fluctuations at Ion-kinetic Scales
• Observational evidence for solar wind proton heating by ion-scale turbulence
• Magnetic helicity signature and its role in regulating magnetic energy spectra and proton temperatures in the solar wind
• Mixing the solar wind proton and electron scales. Theory and 2D-PIC simulations of firehose instability
• Coherence of ion cyclotron resonance for damping ion cyclotron waves in space plasmas
• Growth of Outward Propagating Fast-Magnetosonic/Whistler Waves in the Inner Heliosphere Observed by Parker Solar Probe
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• Temperature anisotropy instabilities of solar wind electrons with regularized Kappa-halos resolved with ALPS
• Does Turbulence along the Coronal Current Sheet Drive Ion Cyclotron Waves?
• Numerical simulations of temperature anisotropy instabilities stimulated by suprathermal protons
• A novel machine learning technique to identify and categorize plasma waves in spacecraft measurements