Abstract
Abstract
We use fluctuating magnetic helicity to investigate the polarization properties of Alfvénic fluctuations at ion-kinetic scales in the solar wind as a function of β
p
, the ratio of proton thermal pressure to magnetic pressure, and θ
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 Alfvénic 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 Alfvén waves. We also investigate the dependence of proton temperature in the β
p
–θ
vB
plane to probe for possible signatures of turbulent dissipation, finding that it correlates with θ
vB
. The proton temperature parallel to
B
0 is higher in the parameter space where we measure the helicity of right-handed Alfvénic 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 θ
vB
in the solar wind we can analyze the dependence of the turbulence distribution on θ
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 θ
vB
in determining proton temperature in the solar wind.
Funder
UKRI ∣ Science and Technology Facilities Council
NSF ∣ GEO ∣ Division of Atmospheric and Geospace Sciences
National Aeronautics and Space Administration
Publisher
American Astronomical Society
Subject
Space and Planetary Science,Astronomy and Astrophysics
Cited by
9 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献