Variations in the chorus source location deduced from fluctuations of the ambient magnetic field: Comparison of Cluster data and the backward wave oscillator model

0313458 - ÚFA 2009 RIV US eng J - Journal Article
Kozelov, B. V. - Demekhov, A. G. - Titova, E. E. - Trakhtengerts, V. Y. - Santolík, Ondřej - Macúšová, Eva - Gurnett, D. A. - Pickett, J. S.
Variations in the chorus source location deduced from fluctuations of the ambient magnetic field: Comparison of Cluster data and the backward wave oscillator model.
[Variace zdrojové oblasti emisí typu chorus určené z fluktuací magnetického pole: porovnání dat družic Cluster a modelu oscilátoru se zpětnou vazbou.]
Journal of Geophysical Research. Roč. 113, A6 (2008), A06216/1-A06216/10. ISSN 0148-0227
R&D Projects: GA AV ČR IAA301120601
Grant - others:NSF(US) 0307319
Institutional research plan: CEZ:AV0Z30420517
Keywords : chorus emissions * backward-wave oscillator model * VLF chorus * BWO model * wave-particle interaction
Subject RIV: BL - Plasma and Gas Discharge Physics
Impact factor: 3.147, year: 2008

We study the motion of the source region of magnetospheric chorus emissions using multipoint measurements of VLF wave emissions and geomagnetic field onboard the Cluster spacecraft. The geomagnetic field data are matched to a parameterized model of the local magnetic field, and the spatiotemporal dynamics of the magnetic field are obtained on this basis. The wave data from the Wide Band Data instrument are used to obtain the power spectral density and number of chorus elements. Comparison of these data shows that the chorus remains related to the magnetic field minimum, while the position of this minimum can vary rather strongly during periods of enhanced geomagnetic activity. These results support the backward wave oscillator (BWO) model of chorus emissions, which attributes chorus generation to an absolute instability of whistler mode waves in the presence of a step-like velocity distribution of energetic electrons. Such an instability takes place in a small vicinity of the local "magnetic equator".

Studie kombinující experimentální měření (data družic Cluster) a teoretického modelu (model oscilátoru se zpětnou vazbou) pro pochopení některých aspektů emisí typu chorus.
Permanent Link: http://hdl.handle.net/11104/0164270