The Radial Variation of the Solar Wind Turbulence Spectra near the Kinetic Break Scale from Parker Solar Probe Measurements

S. Lotz, Amore E. Nel, R. T. Wicks, O. W. Roberts, Nicholas Eugene Engelbrecht, Roelf Du Toit Strauss*, G. J. J. Botha, Eduard P. Kontar, Alexander Pitňa, S. D. Bale

*Corresponding author for this work

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Abstract

In this study we examine the radial dependence of the inertial and dissipation range indices, as well as the spectral break separating the inertial and dissipation range in power density spectra of interplanetary magnetic field fluctuations using Parker Solar Probe data from the fifth solar encounter between ∼0.1 and ∼0.7 au. The derived break wavenumber compares reasonably well with previous estimates at larger radial distances and is consistent with gyro-resonant damping of Alfvénic fluctuations by thermal protons. We find that the inertial scale power-law index varies between approximately −1.65 and −1.45. This is consistent with either the Kolmogorov (−5/3) or Iroshnikov–Kraichnan (−3/2) values, and has a very weak radial dependence with a possible hint that the spectrum becomes steeper closer to the Sun. The dissipation range power-law index, however, has a clear dependence on radial distance (and turbulence age), decreasing from −3 near 0.7 au (4 days) to −4 [±0.3] at 0.1 au (0.75 days) closer to the Sun.
Original languageEnglish
Article number93
JournalThe Astrophysical Journal
Volume942
Issue number2
DOIs
Publication statusPublished - 17 Jan 2023

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