Spectral Features in Field-aligned Solar Wind Turbulence from Parker Solar Probe Observations

Author
Keywords
Abstract
<p>Parker Solar Probe (PSP) observed a large variety of Alfv\ enic fluctuations in the fast and slow solar wind flow during its two perihelia. The properties of Alfv\ enic solar wind turbulence have been studied for decades in the near-Earth environment. A spectral index of -5/3 or -2 for magnetic field fluctuations has been observed using spacecraft measurements, which can be explained by turbulence theories of nearly incompressible magnetohydrodynamics (NI MHD) or critical balance. In this study, a rigorous search of field-aligned solar wind is applied to PSP measurements for the first time, which yields two events in the apparently slow solar wind. The parallel spectra of the magnetic fluctuations in the inertial range show a <em>k</em>\&nbsp;-5/3\&nbsp;||\&nbsp;\&nbsp;k||-5/3 power law. Probability distributions of the magnetic field show that these events are not contaminated by intermittent structures, which, according to previous studies, are known to modify spectral properties. The results presented here are consistent with spectral predictions from NI MHD theory and further deepen our understanding of the Alfv\ enic solar wind turbulence near the Sun.</p>
Year of Publication
2020
Journal
The Astrophysical Journal
Volume
898
Number
Number of Pages
113
Date Published
08/2020
URL
https://iopscience.iop.org/article/10.3847/1538-4357/ab9b7e
DOI
10.3847/1538-4357/ab9b7e