Quantitative effects of cyclotron resonance on the coupling of ULF with VLF and langmuir waves

Abstract

The renewed interest in nonlinear wave–wave coupling phenomena is motivated by the observations of radiation belt storm probes (RBSP) in the Earth's magnetosphere. The recent studies on this subject are mainly limited to the qualitative explanations of RBSP satellites observations. In magnetized plasmas like solar wind, Earth's magnetosphere and many astrophysical environments electrons and ions spiraling along magnetic field lines during cyclotron motion can interfere with the turbulent wave–wave coupling phenomena. This work quantitatively shows that cyclotron resonance plays a complementary role in understanding the turbulent wave–wave coupling in magnetized plasma. It is considered that electrons are in cyclotron resonance with very-low-frequency (VLF) waves, which are coupled with Langmuir oscillations and ultra-low-frequency (ULF) waves. Several illustrative examples are presented. It is found that the resonant electron pitch angles and energy seriously affect the coupling of VLF, ULF, and Langmuir waves. Our findings are important for understanding turbulence in magnetotail region of Earth's magnetosphere.