New Observations of Solar Wind 1/f Turbulence Spectrum from Parker Solar Probe

Abstract

The trace magnetic power spectrum in the solar wind is known to be characterized by a double power law at scales much larger than the proton gyro-radius, with flatter spectral exponents close to -1 found at the lower frequencies below an inertial range with indices closer to $[-1.5,-1.6]$. The origin of the $1/f$ range is still under debate. In this study, we selected 109 magnetically incompressible solar wind intervals ($\delta |\mathbf{B}|/|\mathbf{B}|\ll 1$) from Parker Solar Probe encounters 1 to 13 which display such double power laws, with the aim of understanding the statistics and radial evolution of the low frequency power spectral exponents from Alfvén point up to 0.3 AU. New observations from closer to the sun show that in the low frequency range solar wind turbulence can display spectra much shallower than $1/f$, evolving asymptotically to $1/f$ as advection time increases, indicating a dynamic origin for the $1/f$ range formation. We discuss the implications of this result on the Matteini et al. (2018) conjecture for the $1/f$ origin as well as example spectra displaying a triple power law consistent with the model proposed by Chandran et al. (2018), supporting the dynamic role of parametric decay in the young solar wind. Our results provide new constraints on the origin of the $1/f$ spectrum and further show the possibility of the coexistence of multiple formation mechanisms.

Accepted by ApJL

References in corpus (29)

• Array Programming with NumPy
• The Evolution and Role of Solar Wind Turbulence in the Inner Heliosphere
• Switchbacks in the near-Sun magnetic field: long memory and impact on the turbulence cascade
• First in-situ Measurements of Electron Density and Temperature from Quasi-Thermal Noise Spectroscopy with Parker Solar Probe/FIELDS
• Parker Solar Probe: Four Years of Discoveries at Solar Cycle Minimum
• Magnetic field kinks and folds in the solar wind
• On the 1/f spectrum in the solar wind and its connection with magnetic compressibility
• Switchbacks: statistical properties and deviations from alfvénicity
• Sub-Alfvenic Solar Wind observed by PSP: Characterization of Turbulence, Anisotropy, Intermittency, and Switchback
• Evolution of switchbacks in the inner Heliosphere
• Alfvénic versus non-Alfvénic turbulence in the inner heliosphere as observed by Parker Solar Probe
• Statistical analysis of orientation, shape, and size of solar wind switchbacks
• The low-frequency break observed in the slow solar wind magnetic spectra
• Turbulence characteristics of switchbacks and non-switchbacks intervals observed by \emph{Parker Solar Probe}
• Applicability of Taylor's Hypothesis during Parker Solar Probe perihelia
• Acceleration of polytropic solar wind: Parker Solar Probe observation and one-dimensional model
• Proton Core Behaviour Inside Magnetic Field Switchbacks
• The parametric instability of Alfvén waves: effects of temperature anisotropy
• Multiscale Solar Wind Turbulence Properties inside and near Switchbacks measured by Parker Solar Probe
• Patches of magnetic switchbacks and their origins
• Magnetic field spectral evolution in the inner heliosphere
• The Parametric Decay Instability of Alfven waves in Turbulent Plasmas and the Applications in the Solar Wind
• Magnetic field intermittency in the solar wind: PSP and SolO observations ranging from the Alfven region out to 1 AU
• Phase mixing and the 1/f spectrum in the solar wind
• Time domain structures and dust in the solar vicinity: Parker Solar Probe observations
• Analysis of the distribution, rotation and scale characteristics of solar wind switchbacks: comparison between the first and second encounters of Parker Solar Probe
• How Alfvén waves energize the solar wind: heat vs work
• Conservation of Total Wave Action in the Expanding Solar Wind
• Exact nonlinear solutions for three-dimensional Alfvén-wave packets in relativistic magnetohydrodynamics

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• On the evolution of the Anisotropic Scaling of Magnetohydrodynamic Turbulence in the Inner Heliosphere
• Dominance of 2-Minute Oscillations near the Alfvén Surface
• A Two-dimensional Numerical Study of Ion-Acoustic Turbulence
• Formation of Magnetic Switchbacks via expanding Alfvén Waves
• Evolution of MHD turbulence in the expanding solar wind: residual energy and intermittency
• Two Types of $1/f$ Range in Solar Wind Turbulence
• Interplanetary magnetic correlation and low-frequency spectrum over many solar rotations
• Ion-Scale Solitary Structures in the Solar Wind Observed by Solar Orbiter and Parker Solar Probe