Anisotropy of Magnetic Field Spectra at Kinetic Scales of Solar Wind Turbulence as Revealed by Parker Solar Probe in the Inner Heliosphere

Abstract

Using the Parker Solar Probe data taken in the inner heliosphere, we investigate the power and spatial anisotropy of magnetic-field spectra at kinetic scales (i.e., around sub-ion scales) in solar wind turbulence in the inner heliosphere. We find that strong anisotropy of magnetic spectra occurs at kinetic scales with the strongest power in the perpendicular direction with respect to the local magnetic field (forming an angle theta_B with the mean flow velocity). The spectral index of magnetic spectra varies from -3.2 to -5.8 when the angle theta_B changes from 90 to 180 (or 0) deg, indicating that strong anisotropy of the spectral indices occurs at kinetic scales in the solar wind turbulence. Using a diagnosis based on the magnetic helicity, we show that the anisotropy of the spectral indices can be explained by the nature of the plasma modes that carry the cascade at kinetic scales. We discuss our findings in light of existing theories and current development in the field.

arXiv comment15 pages, 3 figures, accepted by ApJL

References in corpus (24)

• Astrophysical gyrokinetics: kinetic and fluid turbulent cascades in magnetized weakly collisional plasmas
• Spectrum of magnetohydrodynamic turbulence
• Anisotropic scaling of magnetohydrodynamic turbulence
• Dependence of solar wind power spectra on the direction of the local mean magnetic field
• The Solar Probe Cup on Parker Solar Probe
• Anisotropy of Solar Wind Turbulence between Ion and Electron Scales
• The Anisotropy of Electron MHD Turbulence
• Scaling of the electron dissipation range of solar wind turbulence
• On the Existence of the Kolmogorov Inertial Range in the Terrestrial Magnetosheath Turbulence
• Proton Temperature Anisotropy Variations in Inner Heliosphere Estimated with First Parker Solar Probe Observations
• Kinetic Turbulence in the Terrestrial Magnetosheath: Cluster Observations
• Violation of the zeroth law of turbulence in space plasmas
• On the Interpretation of Magnetic Helicity Signatures in the Dissipation Range of Solar Wind Turbulence
• Energy cascade rate measured in a collisionless space plasma with MMS data and compressible Hall magnetohydrodynamic turbulence theory
• Spectral Features of Magnetic Fluctuations at Proton Scales from Fast to Slow Solar Wind
• Anisotropy of Solar-Wind Turbulence in the Inner Heliosphere at Kinetic Scales: PSP Observations
• The Violation of the Taylor Hypothesis in Measurements of Solar Wind Turbulence
• Turbulence/wave transmission at an ICME-driven shock observed by Solar Orbiter and Wind
• Kinetic Scale Slow Solar Wind Turbulence in the Inner Heliosphere: Co-existence of Kinetic Alfvén Waves and Alfvén Ion Cyclotron Waves
• The Ion Transition Range of Solar Wind Turbulence in the Inner Heliosphere: Parker Solar Probe Observations
• The evolution of compressible solar wind turbulence in the inner heliosphere: PSP, THEMIS and MAVEN observations
• Inertial range magnetic fluctuation anisotropy observed from PSP first seven orbits
• Solar Wind Turbulence Around Mars: Relation Between The Energy Cascade Rate And The Proton Cyclotron Waves Activity
• Observational quantification of three-dimensional anisotropies and scalings of space plasma turbulence at kinetic scales

Cited by in corpus (4)

• Strategies for determining the cascade rate in MHD turbulence: isotropy, anisotropy, and spacecraft sampling
• On the evolution of the Anisotropic Scaling of Magnetohydrodynamic Turbulence in the Inner Heliosphere
• On the scaling and anisotropy of two subranges in the inertial range of solar wind turbulence
• Scaling anisotropy with stationary background field in the near-Sun solar wind turbulence