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Direct Measurement of Low‐Energy Electron Foreshock Beams
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SYSNO ASEP 0510734 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title Direct Measurement of Low‐Energy Electron Foreshock Beams Author(s) Souček, Jan (UFA-U) RID, ORCID
Píša, David (UFA-U) RID, ORCID
Santolík, Ondřej (UFA-U) RID, ORCIDNumber of authors 3 Source Title Journal of Geophysical Research-Space Physics. - : Wiley - ISSN 2169-9380
Roč. 124, č. 4 (2019), s. 2380-2392Number of pages 13 s. Publication form Print - P Language eng - English Country US - United States Keywords plasma waves upstream ; high-frequency waves ; ion-sound-waves ; Langmuir-waves ; solar-wind ; nonthermal electrons ; decay ; oscillations ; mode Subject RIV BL - Plasma and Gas Discharge Physics OECD category Fluids and plasma physics (including surface physics) R&D Projects GA17-08772S GA ČR - Czech Science Foundation (CSF) GJ16-16050Y GA ČR - Czech Science Foundation (CSF) Method of publishing Limited access Institutional support UFA-U - RVO:68378289 UT WOS 000477707800002 EID SCOPUS 85064175144 DOI 10.1029/2019JA026470 Annotation Electrostatic plasma waves above and below the local electron plasma frequency represent a characteristic feature of the foreshock region. These waves are known to be generated by electron beams originating from the bow shock and their spectrum varies from narrowband intense waves close to foreshock edge to weaker broadband emissions further downstream. We present a statistical analysis of electron beams observed in the terrestrial foreshock by the Cluster spacecraft. We compared the energy of foreshock electron beams with the spectrum of electrostatic waves and established a clear correspondence between beam energy and spectrum of the waves. The broadband emissions are correlated with low-energy beams, while high-energy electron beams are associated with narrowband Langmuir waves. Next we solved the linear dispersion relation for a subset of observed electron plasma distributions. We discovered that while the observed electron distributions often exhibit a 'bump on tail' feature necessary for an instability, the observed combination of beam energy, density, and temperature typically corresponds to a stable situation. This indicates that strongly unstable electron beams are quickly dissipated by the quasi-linear processes and only stable or marginally stable beams persist long enough to be observed by the instrument. Workplace Institute of Atmospheric Physics Contact Kateřina Adamovičová, adamovicova@ufa.cas.cz, Tel.: 272 016 012 ; Kateřina Potužníková, kaca@ufa.cas.cz, Tel.: 272 016 019 Year of Publishing 2020 Electronic address https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2019JA026470
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