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, R.T., Roberts, O.W., Engelbrecht, N.E., Strauss, R.D., Botha, G.J.J., 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. Astrophysical Journal, 942(2), 93. (doi: 10.3847/1538-4357/aca903)

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.

• Item Type: Articles
• Additional 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). 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).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Kontar, Professor Eduard
• Authors: Lotz, S., Nel, A.E., Wicks, R.T., Roberts, O.W., Engelbrecht, N.E., Strauss, R.D., Botha, G.J.J., Kontar, E. P., Pitňa, A., and Bale, S.D.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Astrophysical Journal
• Publisher: IOP Publishing
• ISSN: 0004-637X
• ISSN (Online): 1538-4357
• Published Online: 17 January 2023
• Copyright Holders: Copyright © 2023 The Authors
• First Published: First published in Astrophysical Journal 942(2):93
• Publisher Policy: Reproduced under a Creative Commons License

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
306515		PHAS A&A Group STFC Consolidated	Lyndsay Fletcher	Science and Technology Facilities Council (STFC)	ST/T000422/1	P&S - Physics & Astronomy