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

Lotz, S., Nel, A. E., Wicks, Robert, Roberts, O. W., Engelbrecht, N. E., Strauss, R. D., Botha, Gert, Kontar, E. P., Pitňa, A. and Bale, S. D. (2023) The Radial Variation of the Solar Wind Turbulence Spectra near the Kinetic Break Scale from Parker Solar Probe Measurements. The Astrophysical Journal, 942 (2). p. 93. ISSN 0004-637X

Lotz_2023_ApJ_942_93.pdf - Published Version
Available under License Creative Commons Attribution 4.0.

Download (2MB) | Preview
Official URL:


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.

Item Type: Article
Additional Information: Funding information: This work is based on the research supported in part by the National Research Foundation of South Africa (NRF grant Nos. 119424, 120345, 120847, and 137793). Opinions expressed and conclusions arrived at are those of the authors and are not necessarily to be attributed to the NRF. The responsibility of the contents of this work is with the authors. Figures prepared with Matplotlib (Hunter 2007) and certain calculations done with NumPy (Harris et al. 2020). R.T.W. is funded by STFC grant ST/V006320/1. E.P.K. was supported by STFC grant ST/T000422/1. Parker Solar Probe was designed, built, and is now operated by the Johns Hopkins Applied Physics Laboratory as part of NASAs Living with a Star (LWS) program (contract NNN06AA01C). Support from the LWS management and technical team has played a critical role in the success of the Parker Solar Probe mission. Thanks to the FIELDS team for providing data (PI: Stuart D. Bale, UC Berkeley). Thanks to the Solar Wind Electrons, Alphas, and Protons (SWEAP) team for providing data (PI: Justin Kasper, BWX Technologies). Software repository at
Subjects: F300 Physics
F500 Astronomy
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: Elena Carlaw
Date Deposited: 18 Jan 2023 09:10
Last Modified: 18 Jan 2023 09:15

Actions (login required)

View Item View Item


Downloads per month over past year

View more statistics