Whistler Wave Generation by Halo Electrons in the Solar Wind

We present an analysis of simultaneous particle and field measurements from the ARTEMIS spacecraft, which demonstrates that quasi-parallel whistler waves in the solar wind can be generated locally by a bulk flow of halo electrons (whistler heat flux instability). ARTEMIS observes quasi-parallel whis...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2019-01, Vol.870 (1), p.L6
Main Authors: Tong, Yuguang, Vasko, Ivan Y., Pulupa, Marc, Mozer, Forrest S., Bale, Stuart D., Artemyev, Anton V., Krasnoselskikh, Vladimir
Format: Article
Language:English
Subjects:
Anisotropy
Distribution functions
Electron velocity distribution
Flow stability
Fluctuations
Frequency ranges
Growth rate
Heat flux
Heat transfer
instabilities
Instability
plasmas
Solar wind
Spacecraft
Stability analysis
Velocity distribution
Wave generation
waves
Whistler waves
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Summary:We present an analysis of simultaneous particle and field measurements from the ARTEMIS spacecraft, which demonstrates that quasi-parallel whistler waves in the solar wind can be generated locally by a bulk flow of halo electrons (whistler heat flux instability). ARTEMIS observes quasi-parallel whistler waves in the frequency range ∼0.05−0.2fce simultaneously with electron velocity distribution functions that are a combination of counter-streaming core and halo populations. A linear stability analysis shows that the plasma is stable when there are no whistler waves, and it is unstable in the presence of whistler waves. In the latter case, the stability analysis shows that the whistler wave growth time is from a few to 10 seconds at frequencies and wavenumbers that match the observations. The observations clearly demonstrate that the temperature anisotropy of halo electrons crucially affects the heat flux instability onset: a slight anisotropy T /T > 1 may quench the instability, while a slight anisotropy T /T < 1 may significantly increase the growth rate. These results demonstrate that heat flux inhibition is strongly dependent on the microscopic plasma properties.
ISSN:2041-8205
2041-8213
DOI:10.3847/2041-8213/aaf734