太阳风流相互作用区边界压力波中的静电波

Electrostatic waves in pressure waves bounding solar wind stream interaction regions

太阳风高速流-低速流相互作用区域前后边界为一对前向-后向压力波,压力波通常在较大日心距处陡化为前向-反向激波.目前尚不清楚在压力波斜坡中是否存在静电波模式,并像在激波中一样提供能量耗散.在本研究中,我们利用1995—2020年的Wind卫星数据,识别了76个在1 AU附近的压力波事件,发现其中27个压力波(18个前向和9个后向压力波)的斜坡中至少有一个波形,且探测到的静电波模主要包括三种波型:离子声波、朗缪尔波和静电孤立波.在前向压力波斜坡中,主导波模是离子声波,而在反向压力波斜坡中则是朗缪尔波和静电孤立波主导.离子声波可以提供约0.01~2Ω·m的反常电阻率.我们发现离子声波的最大振幅与压力波强度之间存在正相关关系.这些结果表明:对于一些前向压力波,离子声波可以提供潜在的能量耗散.

The solar wind stream interaction region is bounded by a pair of forward-reverse pressure waves that commonly steepen into forward and reverse shock waves at large heliocentric distances.It remains unclear whether electrostatic(ES)wave modes are present in pressure wave ramps and provide energy dissipation as they do in shock waves.In this study,we identified 76 pressure waves bounding SIRs near 1 AU utilizing Wind meas-urements from 1995–2020 and determined that 27 pressure waves(18 forward and nine reverse)had at least one waveform capture in the pressure ramp.The ES wave modes included three main wave types:ion acoustic waves(IAWs),Langmuir waves,and ES solitary waves(ESWs).The dominant mode in the forward pressure wave ramp was the IAW,whereas those in the reverse pressure wave ramp were the Langmuir wave and ESW.The IAWs provided an approximately anomalous resistivity of 0.01–2Ω·m.A positive correlation existed between the maxi-mum of the IAW amplitude and the strength of the pressure wave.These results indicate that IAWs can potentially provide energy dissipation for forward pressure waves.