Energy Transfer from Magnetohydrodynamic-scale Slow-mode Waves to Kinetic-scale Ion Acoustic Waves

Abstract Large-amplitude slow-mode waves are commonly observed near Earth’s magnetopause. Recent observations show that these waves can occur simultaneously with kinetic-scale ion acoustic waves (IAWs). The amplitude of the IAWs is enhanced near the magnetic field peaks of the slow-mode wave, suggesting that the slow-mode waves may drive the generation of IAWs. To test this hypothesis, we conduct a hybrid simulation using observation-based parameters. The simulation results demonstrate that large-amplitude slow-mode waves generate counterstreaming ion beams, which in turn excite IAWs and relax the ion beams. Our study reveals a clear energy transfer channel from magnetohydrodynamic-scale slow-mode waves to kinetic-scale IAWs.