Effects of Field-Aligned Cold Plasma Density Filaments on the Fine Structure of Chorus

0569492 - ÚFA 2023 RIV US eng J - Journal Article
Hanzelka, Miroslav - Santolík, Ondřej
Effects of Field-Aligned Cold Plasma Density Filaments on the Fine Structure of Chorus.
Geophysical Research Letters. Roč. 49, č. 24 (2022), č. článku e2022GL101654. ISSN 0094-8276. E-ISSN 1944-8007
EU Projects: European Commission(XE) 870452 - PAGER
Institutional support: RVO:68378289
Keywords : density ducts * fullwave simulation * signal analysis * Van Allen Probes * wave propagation * whistler-mode chorus
OECD category: Fluids and plasma physics (including surface physics)
Impact factor: 5.2, year: 2022
Method of publishing: Open access
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GL101654

The whistler-mode chorus emission, a major driver of radiation belt electron energization and precipitation, exhibits significant amplitude modulations on millisecond timescales. These subpacket modulations are accompanied by fast changes in the wave normal angle. Understanding the evolution of wave propagation properties inside chorus elements is essential for modeling nonlinear chorus-electron interactions, but the origin of these rapid changes is unclear. We propose that the variations come from propagation inside thin, field-aligned cold plasma enhancements (density ducts), which produce differing modulations in parallel and perpendicular wave magnetic field components. We show that a full-wave simulation on a filamented density background predicts wave vector and amplitude evolution similar to Van Allen Probes spacecraft observations. We further demonstrate that the commonly assumed wide density ducts, in which wave propagation can be studied with ray tracing methods, cannot explain the observed behavior. This indirectly proves the existence of wavelength-scale field-aligned density fluctuations.
Permanent Link: https://hdl.handle.net/11104/0340831