Theories of Growth and Propagation of Parallel Whistler-Mode Chorus Emissions: A Review

0573219 - ÚFA 2025 RIV DE eng J - Journal Article
Hanzelka, Miroslav - Santolík, Ondřej
Theories of Growth and Propagation of Parallel Whistler-Mode Chorus Emissions: A Review.
Surveys in Geophysics. Roč. 45, č. 1 (2024), s. 1-54. ISSN 0169-3298. E-ISSN 1573-0956
EU Projects: European Commission(XE) 870452 - PAGER
Institutional support: RVO:68378289
Keywords : Chorus emission * Whistler mode * Nonlinear growth * Wave-particle interactions * Resonant current * Cyclotron resonance * Space plasma * Plasma waves * Sideband instability * Backwards-wave oscillator
OECD category: Fluids and plasma physics (including surface physics)
Impact factor: 4.6, year: 2022
Method of publishing: Open access
https://link.springer.com/article/10.1007/s10712-023-09792-x

The significant role of nonlinear wave-particle interactions in the macrodynamics and microdynamics of the Earth's outer radiation belt has long been recognised. Electron dropouts during magnetic storms, microbursts in atmospheric electron precipitation, and pulsating auroras are all associated with the rapid scattering of energetic electrons by the whistler-mode chorus, a structured electromagnetic emission known to reach amplitudes of about 1% of the ambient magnetic field. Despite the decades of experimental and theoretical investigations of chorus and the recent progress achieved through numerical simulations, there is no definitive theory of the chorus formation mechanism, not even in the simple case of parallel (one-dimensional) propagation. Here we follow the evolution of these theories from their beginnings in the 1960s to the current state, including newly emerging self-consistent excitation models. A critical review of the unique features of each approach is provided, taking into account the most recent spacecraft observations of the fine structure of chorus. Conflicting interpretations of the role of resonant electron current and magnetic field inhomogeneity are discussed. We also discuss the interplay between nonlinear growth and microscale propagation effects and identify future theoretical and observational challenges stemming from the two-dimensional aspects of chorus propagation.
Permanent Link: https://hdl.handle.net/11104/0343683