Frequency Dependence of Very Low Frequency Chorus Poynting Flux in the Source Region: THEMIS Observations and a Model

0538496 - ÚFA 2021 RIV US eng J - Journal Article
Demekhov, A. G. - Taubenschuss, Ulrich - Hanzelka, Miroslav - Santolík, Ondřej
Frequency Dependence of Very Low Frequency Chorus Poynting Flux in the Source Region: THEMIS Observations and a Model.
Geophysical Research Letters. Roč. 47, č. 6 (2020), č. článku e2020GL086958. ISSN 0094-8276. E-ISSN 1944-8007
EU Projects: European Commission(XE) 870452 - PAGER
Grant - others:AV ČR(CZ) AP1401
Program: Akademická prémie - Praemium Academiae
Institutional support: RVO:68378289
Keywords : VLF chorus * BWO model * Radiation Belts * Hiss * Whistler
OECD category: Fluids and plasma physics (including surface physics)
Impact factor: 4.720, year: 2020
Method of publishing: Open access
https://agupubs.onlinelibrary.wiley.com/doi/pdfdirect/10.1029/2020GL086958

Using Poynting vector measurements of whistler mode chorus emissions detected by the THEMIS spacecraft within the source region, that is, close to the magnetic field minimum, we found both in individual events and statistically that chorus elements propagating equatorward had systematically higher frequencies and smaller amplitudes compared with simultaneously observed elements propagating away from the equator. We demonstrate similar features in the results of numerical simulations based on backward wave oscillator equations. It can be qualitatively explained by the nonlinear evolution of the energetic electron distribution function during wave generation. The motion of electrons from the equator is accompanied by a decrease in their velocity component along the magnetic field line due to both the adiabatic mirror force and nonlinear wave-particle interactions. Thus, the frequency of the chorus elements generated by such electrons and propagating equatorward is higher compared with the elements propagating away from the equator.
Permanent Link: http://hdl.handle.net/11104/0316348