Whistler Fan Instability Driven by Strahl Electrons in the Solar Wind

I. Vasko (1) , Vladimir Krasnoselskikh (2, 1) , Y. Tong (1) , S. Bale (1) , J. Bonnell (1) , F. Mozer (1)

1 SSL - Space Sciences Laboratory [Berkeley]
2 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace

The American Astronomical Society, find out more The American Astronomical Society, find out more The Institute of Physics, find out more The Institute of Physics, find out more Whistler Fan Instability Driven by Strahl Electrons in the Solar Wind I. Y. Vasko1,2 , V. Krasnoselskikh1,3, Y. Tong1,4, S. D. Bale1,4 , J. W. Bonnell1, and F. S. Mozer1 Published 2019 January 31 • © 2019. The American Astronomical Society. All rights reserved. The Astrophysical Journal Letters, Volume 871, Number 2 Download Article PDF DownloadArticle ePub Figures Tables References Download PDF Download ePub 574 Total downloads 19 19 total citations on Dimensions. Turn on MathJax Get permission to re-use this article Share this article Share this content via email Share on Facebook Share on Twitter Share on Google+ Share on Mendeley Hide article information Author affiliations 1 Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA 2 Space Research Institute of Russian Academy of Sciences, Moscow, 177997, Russia 3 LPC2E/CNRS, Orlean, France 4 Physics Department, University of California, Berkeley, CA 94720, USA ORCID iDs I. Y. Vasko https://orcid.org/0000-0002-4974-4786 V. Krasnoselskikh https://orcid.org/0000-0002-6809-6219 Y. Tong https://orcid.org/0000-0002-3354-486X S. D. Bale https://orcid.org/0000-0002-1989-3596 Dates Received 2019 January 18 Accepted 2019 January 24 Published 2019 January 31 Check for updates using Crossmark Citation I. Y. Vasko et al 2019 ApJL 871 L29 Create citation alert DOI https://doi.org/10.3847/2041-8213/ab01bd Keywords conduction; instabilities; plasmas; scattering; solar wind; waves Journal RSS feed Sign up for new issue notifications Abstract We present a theoretical analysis of electron heat flux inhibition in the solar wind when a significant portion of the heat flux is carried by strahl electrons. We adopt core-strahl velocity distribution functions typical for the solar wind at 0.3–4 au to demonstrate that strahl electrons are capable of generating highly oblique whistler waves at wave numbers kρe ~ 1, where ρe is typical thermal electron gyroradius. The whistler waves are driven by electrons in the anomalous cyclotron resonances (the fan instability) and propagate at typical angles of about 70°–80° to the strahl that is usually anti-sunward. The group velocity of the whistler waves is predominantly parallel to the strahl, thereby facilitating efficient scattering of strahl electrons. We suggest that the highly oblique whistler waves drive pitch-angle scattering of strahl electrons, resulting in halo formation and suppressing the heat flux of strahl electrons below a threshold that is shown to depend on βe . The proposed fan instability is fundamentally different from the whistler heat flux instability driven by the normal cyclotron resonance with halo electrons and being ineffective in suppressing the heat flux of the strahl.

Domains: Sciences of the Universe [physics]

I. Vasko, Vladimir Krasnoselskikh, Y. Tong, S. Bale, J. Bonnell, et al.. Whistler Fan Instability Driven by Strahl Electrons in the Solar Wind. The Astrophysical journal letters, 2019, 871 (2), pp.L29. ⟨10.3847/2041-8213/ab01bd⟩. ⟨insu-02941512⟩