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Poynting vector and wave vector directions of equatorial chorus
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SYSNO ASEP 0472232 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title Poynting vector and wave vector directions of equatorial chorus Author(s) Taubenschuss, Ulrich (UFA-U) RID, ORCID
Santolík, Ondřej (UFA-U) RID, ORCID
Breuillard, H. (FR)
Li, W. (US)
Le Contel, O. (FR)Source Title Journal of Geophysical Research-Space Physics. - : Wiley - ISSN 2169-9380
Roč. 121, č. 12 (2016), s. 11912-11928Number of pages 17 s. Language eng - English Country US - United States Keywords whistler-mode waves ; Earth's inner magnetosphere ; Van Allen probes ; plasmaspheric hiss ; magnetic reconnection ; outer magnetosphere ; source region ; emissions ; propagation ; THEMIS Subject RIV BL - Plasma and Gas Discharge Physics R&D Projects GA14-31899S GA ČR - Czech Science Foundation (CSF) LH15304 GA MŠMT - Ministry of Education, Youth and Sports (MEYS) Institutional support UFA-U - RVO:68378289 UT WOS 000393183300020 EID SCOPUS 85007085705 DOI 10.1002/2016JA023389 Annotation We present new results on wave vectors and Poynting vectors of chorus rising and falling tones on the basis of 6 years of THEMIS (Time History of Events and Macroscale Interactions during Substorms) observations. The majority of wave vectors is closely aligned with the direction of the ambient magnetic field (B-0). Oblique wave vectors are confined to the magnetic meridional plane, pointing away from Earth. Poynting vectors are found to be almost parallel to B-0. We show, for the first time, that slightly oblique Poynting vectors are directed away from Earth for rising tones and toward Earth for falling tones. For the majority of lower band chorus elements, the mutual orientation between Poynting vectors and wave vectors can be explained by whistler mode dispersion in a homogeneous collisionless cold plasma. Upper band chorus seems to require inclusion of collisional processes or taking into account azimuthal anisotropies in the propagation medium. The latitudinal extension of the equatorial source region can be limited to +/- 6 degrees around the B-0 minimum or approximately +/- 5000 km along magnetic field lines. We find increasing Poynting flux and focusing of Poynting vectors on the B-0 direction with increasing latitude. Also, wave vectors become most often more field aligned. A smaller group of chorus generated with very oblique wave normals tends to stay close to the whistler mode resonance cone. This suggests that close to the equatorial source region (within similar to 20 degrees latitude), a wave guidance mechanism is relevant, for example, in ducts of depleted or enhanced plasma density. 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 2017
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