Magnetic field spectral evolution in the inner heliosphere

Abstract

Parker Solar Probe and Solar Orbiter data are used to investigate the radial evolution of magnetic turbulence between $0.06\lesssim R\lesssim 1$ au. The spectrum is studied as a function of scale, normalized to the ion inertial scale $d_i$. In the vicinity of the Sun, the inertial range is limited to a narrow range of scales and exhibits a power-law exponent of, ${\alpha }_B=-3/2$, independent of plasma parameters. The inertial range grows with distance, progressively extending to larger spatial scales, while steepening towards a ${\alpha }_B=-5/3$ scaling. It is observed that spectra for intervals with large magnetic energy excesses and low Alfvénic content steepen significantly with distance, in contrast to highly Alfvénic intervals that retain their near-Sun scaling. The occurrence of steeper spectra in slower wind streams may be attributed to the observed positive correlation between solar wind speed and Alfvénicity.

Accepted to APJ letters with minor revisions

References in corpus (10)

• The Solar Orbiter mission -- Science overview
• Anisotropic scaling of magnetohydrodynamic turbulence
• The Evolution and Role of Solar Wind Turbulence in the Inner Heliosphere
• First in-situ Measurements of Electron Density and Temperature from Quasi-Thermal Noise Spectroscopy with Parker Solar Probe/FIELDS
• Three-dimensional simulation of the fast solar wind driven by compressible magnetohydrodynamic turbulence
• The Radial Dependence of Proton-scale Magnetic Spectral Break in Slow Solar Wind during PSP Encounter 2
• Intermittency in the Expanding Solar Wind: Observations from Parker Solar Probe (0.16au), Helios 1 (0.3-1au), and Voyager 1 (1-10au)
• A Modified Version of Taylor's Hypothesis for Solar Probe Plus Observations
• Patches of magnetic switchbacks and their origins
• Magnetic field intermittency in the solar wind: PSP and SolO observations ranging from the Alfven region out to 1 AU

Cited by in corpus (9)

• An Anisotropic Density Turbulence Model from the Sun to 1 au Derived From Radio Observations
• New Observations of Solar Wind 1/f Turbulence Spectrum from Parker Solar Probe
• Turbulence Properties of Interplanetary Coronal Mass Ejections in the Inner Heliosphere: Dependence on Proton Beta and Flux Rope Structure
• Evidence for the helicity barrier from measurements of the turbulence transition range in the solar wind
• Dominance of 2-Minute Oscillations near the Alfvén Surface
• 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
• The impact of Alfvenic shear flow on magnetic reconnection and turbulence
• Interplanetary magnetic correlation and low-frequency spectrum over many solar rotations