Impact of Residual Energy on Solar Wind Turbulent Spectra

Abstract

It is widely reported that the power spectra of magnetic field and velocity fluctuations in the solar wind have power law scalings with inertial-range spectral indices of -5/3 and -3/2 respectively. Studies of solar wind turbulence have repeatedly demonstrated the impact of discontinuities and coherent structures on the measured spectral index. Whether or not such discontinuities are self-generated by the turbulence or simply observations of advected structures from the inner heliosphere has been a matter of considerable debate. This work presents a statistical study of magnetic field and velocity spectral indices over 10 years of solar-wind observations; we find that anomalously steep magnetic spectra occur in magnetically dominated intervals with negative residual energy. However, this increase in negative residual energy has no noticeable impact on the spectral index of the velocity fluctuations, suggesting that these intervals with negative residual energy correspond to intermittent magnetic structures. We show statistically that the difference between magnetic and velocity spectral indices is a monotonic function of residual energy, consistent with previous work which suggests that intermittency in fluctuations causes spectral steepening. Additionally, a statistical analysis of cross helicity demonstrates that when the turbulence is balanced (low cross-helicity), the magnetic and velocity spectral indices are not equal, which suggests that our observations of negative residual energy and intermittent structures are related to non-linear turbulent interactions rather than the presence of advected pre-existing flux-tube structures.

References in corpus (15)

• Spectrum of magnetohydrodynamic turbulence
• Simulations of Incompressible MHD Turbulence
• Spectral energy dynamics in magnetohydrodynamic turbulence
• Finite dissipation and intermittency in magnetohydrodynamics
• Radial evolution of solar wind intermittency in the inner heliosphere
• Role of cross helicity in magnetohydrodynamic turbulence
• Residual Energy Spectrum of Solar Wind Turbulence
• Disruption of sheetlike structures in Alfvénic turbulence by magnetic reconnection
• Spectral scaling laws in MHD turbulence simulations and in the solar wind
• A statistical model of three-dimensional anisotropy and intermittency in strong Alfvénic turbulence
• Correlations at large scales and the onset of turbulence in the fast solar wind
• Measures of Three-Dimensional Anisotropy and Intermittency in Strong Alfvénic Turbulence
• Alignment and scaling of large-scale fluctuations in the solar wind
• Density Fluctuations in the Solar Wind Driven by Alfvén Wave Parametric Decay
• Alfvén-dynamo balance and magnetic excess in MHD turbulence

Cited by in corpus (17)

• The Evolution and Role of Solar Wind Turbulence in the Inner Heliosphere
• Parker Solar Probe: Four Years of Discoveries at Solar Cycle Minimum
• Cross Helicity Reversals In Magnetic Switchbacks
• The Radial Dependence of Proton-scale Magnetic Spectral Break in Slow Solar Wind during PSP Encounter 2
• Turbulence characteristics of switchbacks and non-switchbacks intervals observed by \emph{Parker Solar Probe}
• The Near-Sun Streamer Belt Solar Wind: Turbulence and Solar Wind Acceleration
• Multiscale Solar Wind Turbulence Properties inside and near Switchbacks measured by Parker Solar Probe
• Magnetic field spectral evolution in the inner heliosphere
• Cross Helicity of the November 2018 Magnetic Cloud Observed by the Parker Solar Probe
• Origin of Multifractality in Solar Wind Turbulence: the Role of Current Sheets
• Three-dimensional local anisotropy of velocity fluctuations in the solar wind
• Kinetic Scale Spectral Features of Cross Helicity and Residual Energy in the Inner Heliosphere
• Effect of Spherical Polarization on the Magnetic Spectrum of the Solar Wind
• Evolution of MHD turbulence in the expanding solar wind: residual energy and intermittency
• Intermittency in Interplanetary Coronal Mass Ejections Observed by Parker Solar Probe and Solar Orbiter
• The impact of Alfvenic shear flow on magnetic reconnection and turbulence
• Residual Energy and Broken Symmetry in Reduced Magnetohydrodynamics