English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We use magnetic helicity to characterise solar wind fluctuations atproton-kinetic scales from Wind observations. For the first time, we separatethe contributions to helicity from fluctuations propagating at anglesquasi-parallel and oblique to the local mean magnetic field, $\mathbf{B}_0$. Wefind that the helicity of quasi-parallel fluctuations is consistent withAlfv\'en-ion cyclotron and fast magnetosonic-whistler modes driven by protontemperature anisotropy instabilities and the presence of a relative driftbetween $\alpha$-particles and protons. We also find that the helicity ofoblique fluctuations has little dependence on proton temperature anisotropy andis consistent with fluctuations from the anisotropic turbulent cascade. Ourresults show that parallel-propagating fluctuations at proton-kinetic scales inthe solar wind are dominated by proton temperature anisotropy instabilities andnot the turbulent cascade. We also provide evidence that the behaviour offluctuations at these scales is independent of the origin and macroscopicproperties of the solar wind.

Parallel-propagating Fluctuations at Proton-kinetic Scales in the Solar Wind are Dominated by Kinetic Instabilities