日侧外磁层ULF波调制EMIC波的MMS观测

磁层多尺度卫星(MMS-1)在日侧06:30 MLT(磁地方时,Magnetic Local Time)外磁层大于2Re(L为7.5～10.1)的范围内观测到多达21个波包的准周期性电磁离子回旋波(EMIC)事件.超低频(ULF)波和能量质子温度各向异性准周期性增强也被同步观测到.频率分析显示,ULF波的周期、质子各向...

Magnetospheric Multiscale Observation of Electromagnetic Ion Cyclotron Wave Modulated by ULF Wave in Outer Magnetosphere

A quasi-periodic Electromagnetic Ions Cyclotron (EMIC) wave event was reported. The event was observed by the Magnetospheric Multiscale (MMS-1) at dayside (06:30 MLT) in the outer magnetosphere. EMIC waves with more than 21 wave packets occurred within L value is from 7.5 to 10.1. Ultra-Low Frequency (ULF) waves and the quasi-periodic enhancement of energy protons temperature anisotropy are simultaneously observed. Frequency analysis shows that the period of the ULF wave, the proton anisotropy period and the period of the EMIC wave packet are very close. The MMS-4 satellite passed the very close region about an hour later and found that the quasi-periodicity of the EMIC wave packet decreased as the amplitude of the ULF wave decreased. The current results provide evidences that the ULF wave can modulate the energetic proton anisotropy in the outer magnetosphere at dayside and thus generate periodic EMIC wave packets. Moreover, correlated observations by MMS-1 and MMS-4 show that the ULF-modulation of EMIC waves can occur in a spatial scale that greater than 2 R_e, and last for several hours.