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Nonlinear Damping of Oblique Whistler Mode Waves Via Landau Resonance
Author(s) -
Hsieh YiKai,
Omura Yoshiharu
Publication year - 2018
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2018ja025848
Subject(s) - landau damping , physics , resonance (particle physics) , cyclotron resonance , electron , landau quantization , whistler , quantum electrodynamics , atomic physics , condensed matter physics , cyclotron , quantum mechanics
Nonlinear trapping of electrons via Landau resonance is an important mechanism of oblique whistler mode wave‐particle interactions. Electrons trapped by Landau resonance gain energies from waves. The Landau resonance velocity becomes very close to the group velocity of nearly parallel whistler mode waves at frequencies around half the electron gyrofrequency, resulting in a long interaction time and possible wave damping. We perform test particle simulations with parameters at L = 5 and a small wave normal angle 10° to study the wave‐particle interactions via the Landau resonance. Analyzing the wave electric fields and the resonant currents formed by electrons undergoing Landau and cyclotron resonances, we show that effective wave damping occurs near half the electron gyrofrequency. This nonlinear wave damping is contributed by Landau resonance rather than cyclotron resonance. Furthermore, we confirm that this damping is dominated by perpendicular components of the wave electric field and perpendicular resonant currents. The simulation results indicate that nonlinear damping via Landau resonance is one of the mechanisms dividing chorus emissions into the upper band and the lower band.