磁尾等离子体片中周期性高速流相伴随磁场超低频波

本文利用Cluster卫星2004年11月8日的观测数据，分析了磁尾等离子体片中与地向周期性高速离子流相伴随的ULF波.结果显示周期性高速流的速度波动与磁场和温度中的ULF波同时出现、同时增强、同时消失，而且波动的频率都集中在60~70 mHz.这说明磁场和温度ULF波与周期性高速流密切相关，周期性高速流是ULF波产生的来源.高速流波动的相位与磁场波动的相位大致反相关，与热离子温度波动的相位正相关，同时磁场波动与热离子温度波动呈相位反相关的特性.最小方差法分析的结果显示虽然波传播方向有地向分量，但其主要传播方向是向等离子体片中心传播，并与周期性高速流速度方向垂直.以上观测说明是高速流的周期性变化产生了磁场在Pi1频率范围内的ULF波.

ULF waves associated with the periodical high speed flows in magnetotail plasma sheet

In this paper, using the data of Cluster on 8 November 2004, we analyze the ULF wave associated with earthward periodical high speed flow in the plasma sheet. The results show that the ULF waves in the magnetic field and temperature appear, enhance and end at the same times with those of periodical high speed ion flow. Particularly, the oscillation frequencies in ion flow velocity, magnetic field and ion temperature are all between 60～70 mHz, I.e. In the frequency range of Pil. These observations show that there is a close correlation among the ULF wave in the magnetic field, temperature and periodical high speed flow. The oscillations of the high speed flow is approximately out of phase with the ULF wave in the magnetic field, and in phase with the ULF wave in the temperature. The results of Minimum Variance Analysis show that although the wave propagation direction includes earthward component, the main propagation direction is towards the centre of plasma sheet and perpendicular to both the high speed flow velocity and magnetic field. All these observations indicate that the periodical high speed flow can generate the ULF waves at the same frequency.