通量堆积和偶极化过程中的超低频波动

2004年9月17日TC-1卫星在近地磁尾夜侧观测到一次伴随有通量堆积和偶极化过程的典型亚暴事件.本文利用离散小波分析和FFT分析方法对本次事件中4 s精度的FGM和HIA数据进行分析，以了解通量堆积过程和偶极化过程中的低频波特性.分析结果表明，通量堆积过程和偶极化过程中场和粒子有明显的不规则低频波动，主要波动频率范围为4~15 mHz，和Pi-2脉动一致.通量堆积过程中磁场各个分量的低频波动和偶极化过程中的低频波动有明显不同，表明这两个物理过程可能存在不同的波动机制.在通量堆积过程和偶极化过程中，平行磁场方向上温度和速度的波动和垂直方向上温度和速度的波动有明显区别，平行磁场方向上温度和速度的波动有较好的相关性，且热离子密度的波动和平行磁场方向上的波动有较好的相关性，表明存在快模压缩波.TC-1卫星的观测显示通量堆积过程中磁场By分量有明显增长.我们的分析结果表明ULF波与By分量的增长有密切关系，从而可能对亚暴膨胀相的触发有重要影响.

The ULF wave in the pile-up and dipolarization process

A typical substorm process in the night-side near-Earth magnetotail company with the pile-up and depolarization process explored by TC-1 on sep 17,2004.We analyzed the FGM and HIA data(4s resolution)with wavelet and FFT analysis method to understand the low-frequency wave in the pile-up and dipolarization process.The analysis results showed that there are distinctly irregular low-frequency wave in the pile-up and dipolarization process,the main range of the wave frequency is 4~15 mHz,coincident with the Pi-2 pulse.The LF wave of the each magnetic field component in the dipoarization process is distinctly different with that in the pile-up process.During the pileup and dipolarization process,the wave of the temperature and velocity in the direction parallel to the magnetic field is distinctly with that in the direction perpendicular to the magnetic field.It seems the wave of the temperature and velocity in the direction parallel to the magnetic field has good correlation,and the wave of the ions density has good correlation with the wave in the direction parallel to the magnetic field,which means there exist compressive wave in the direction parallel the magnetic field.The exploration by the TC-1 showed that there are distinct increase of the By component in the pile-up process.The ULF wave has closely correlation with increase By component,and may has important effect of the substorm onset.