Dependence of Solar Wind Proton Temperature on the Polarization Properties of Alfvenic Fluctuations at Ion-kinetic Scales

L. D. Woodham; R. T. Wicks; D. Verscharen; J. M. TenBarge; G. G. Howes

doi:10.3847/1538-4357/abed51

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Dependence of Solar Wind Proton Temperature on the Polarization Properties of Alfvenic Fluctuations at Ion-kinetic Scales

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Dependence of Solar Wind Proton Temperature on the Polarization Properties of Alfvenic Fluctuations at Ion-kinetic Scales

L. D. Woodham, R. T. Wicks, D. Verscharen, J. M. TenBarge and G. G. Howes

The Astrophysical journal, Vol.912(2), p.101

05/10/2021

DOI: 10.3847/1538-4357/abed51

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Abstract

We use fluctuating magnetic helicity to investigate the polarization properties of Alfvenic fluctuations at ion-kinetic scales in the solar wind as a function of beta ( p ), the ratio of proton thermal pressure to magnetic pressure, and theta ( vB ), the angle between the proton flow and local mean magnetic field, B (0). Using almost 15 yr of Wind observations, we separate the contributions to helicity from fluctuations with wavevectors, k , quasi-parallel and oblique to B (0), finding that the helicity of Alfvenic fluctuations is consistent with predictions from linear Vlasov theory. This result suggests that the nonlinear turbulent fluctuations at these scales share at least some polarization properties with Alfven waves. We also investigate the dependence of proton temperature in the beta ( p )-theta ( vB ) plane to probe for possible signatures of turbulent dissipation, finding that it correlates with theta ( vB ). The proton temperature parallel to B (0) is higher in the parameter space where we measure the helicity of right-handed Alfvenic fluctuations, and the temperature perpendicular to B (0) is higher where we measure left-handed fluctuations. This finding is inconsistent with the general assumption that by sampling different theta ( vB ) in the solar wind we can analyze the dependence of the turbulence distribution on theta ( kB ), the angle between k and B (0). After ruling out both instrumental and expansion effects, we conclude that our results provide new evidence for the importance of local kinetic processes that depend on theta ( vB ) in determining proton temperature in the solar wind.

Physical Sciences

Astronomy & Astrophysics

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Title: Subtitle: Dependence of Solar Wind Proton Temperature on the Polarization Properties of Alfvenic Fluctuations at Ion-kinetic Scales
Creators: L. D. Woodham - Imperial College London
R. T. Wicks - Northumbria University
D. Verscharen - University College London
J. M. TenBarge - Princeton University
G. G. Howes - University of Iowa
Resource Type: Journal article
Publication Details: The Astrophysical journal, Vol.912(2), p.101
DOI: 10.3847/1538-4357/abed51
ISSN: 0004-637X
eISSN: 1538-4357
Publisher: IOP Publishing Ltd
Number of pages: 13
Grant note: ST/P003826/1 / STFC Ernest Rutherford Fellowship; UK Research & Innovation (UKRI); Science & Technology Facilities Council (STFC) ST/N504488/1 / STFC studentship at UCL/MSSL ST/S000364/1; ST/N000722/1; ST/S000240/1 / STFC; UK Research & Innovation (UKRI); Science & Technology Facilities Council (STFC) 80NSSC18K1217; 80NSSC18K0643 / NASA; National Aeronautics & Space Administration (NASA) AGS-1622306 / NSF SHINE award; National Science Foundation (NSF); NSF - Directorate for Geosciences (GEO)
Language: English
Date published: 05/10/2021
Academic Unit: Physics and Astronomy
Record Identifier: 9984428792602771

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