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  Gap formation around Ωe/2 and generation of low-band whistler waves by Landau-resonant electrons in the magnetosphere: Predictions from dispersion theory

Sauer, K., Baumgärtel, K., & Sydora, R. (2020). Gap formation around Ωe/2 and generation of low-band whistler waves by Landau-resonant electrons in the magnetosphere: Predictions from dispersion theory. Earth and Planetary Physics, 4(2), 138-150. doi:10.26464/epp2020020.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0006-F528-9 Version Permalink: http://hdl.handle.net/21.11116/0000-0006-F529-8
Genre: Journal Article

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 Creators:
Sauer, Konrad1, Author
Baumgärtel, Klaus, Author
Sydora, Richard, Author
Affiliations:
1Max Planck Institute for Solar System Research, Max Planck Society, Justus-von-Liebig-Weg 3, 37077 Göttingen, DE, ou_1125546              

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 Abstract: In this paper we show that two significant phenomena of magnetospheric chorus emission can be explained by the participation of beam-like electron structures, created by Landau-resonant interaction with growing oblique whistler waves. The first concerns the widely observed spectral gap near half the electron cyclotron frequency Ωe; the second is related to the observation of very obliquely propagating lower-band waves that cannot be directly generated by temperature anisotropy. Concerning the gap, kinetic dispersion theory reveals that interference of the beam-related cyclotron mode ω~Ωe-kVb with the conventional whistler mode leads to mode splitting and the appearance of a ‘forbidden’ area in the ω-k space. Thereby the beam velocity Vb appears as an essential parameter. It is directly related to the phase velocity of the most unstable whistler wave mode, which is close to VAe/2 for sufficiently hot electrons (VAe is the electron Alfven velocity). To clarify the second point, we show that Landau-resonant beams with Vb < VAe/2, which arise in cold plasmas from unstable upper-band waves, are able to generate lower-band whistler mode waves at very oblique propagation (θ ≥ 60°). Our studies demonstrate the important role of Landau-resonant electrons in nonlinear whistler wave generation in the magnetosphere.

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Language(s): eng - English
 Dates: 2020
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.26464/epp2020020
 Degree: -

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Title: Earth and Planetary Physics
  Other : EPP
Source Genre: Journal
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Publ. Info: Wiley
Pages: - Volume / Issue: 4 (2) Sequence Number: - Start / End Page: 138 - 150 Identifier: ISSN: 2096-3955
CoNE: https://pure.mpg.de/cone/journals/resource/2096-3955