Multi-scale pressure-balanced structures in the solar wind observed by WIND  

作　　者：YAO Shuo TU ChuanYi HE JianSen2 WEI WenBo MENG XiaoHong 

机构地区：[1]School of Geophysics and Information Technology, China University of Geosciences （Beijing）, Beijing 100083, China [2]School of Earth and Space Sciences, Peking University, Beijing 100871, China

出　　处：《Chinese Science Bulletin》2012年第12期1421-1428,共8页

基　　金：supported by the Fundamental Research Funds for the Central Universities(2011YYL127);supported by the National Natural Science Foundation of China(40874090,40931055 and 40890162)

摘　　要：This work detects multi-scale, from hour to seconds, pressure-balanced structures (PBSs) in the solar wind based on the anti- correlation between the plasma thermal pressure and the magnetic pressure measured by WIND at 1 AU on April 5th, 2001. In our former research based on Cluster measurements, we showed the anti-correlation between the electron density and the magnetic field strength in multi-scales, and we supposed these structures may be pressure-balanced structures. Thus, in this work we aim to prove our speculation by the direct evidence on pressure measurements. Different from our previous work, we apply the WIND measurements this time, for they have both the magnetic pressure and the plasma pressure which Cluster could not offer. We use the wavelet cross-coherence method to analyze the correlation between the plasma pressure (P th ) and the magnetic pressure (P B ), and also the electron density (N e ) and the magnetic field strength (B) on various scales. We observe the anti-correlation between P th and P B distributed at different temporal scales ranging from 1000 s down to 10 s. This result directly indicates the existence of pressure- balanced structures (PBSs) with different sizes in the solar wind. Further, We compare the wavelet cross correlation spectrum of P th -P B and N e -B. We notice that the two spectra are similar in general. Thus this result confirms that the relation between P th -P B and N e -B are consistent with each other in the PBSs we study. Moreover, we compare the power spectrum density (PSD) of relative N e fluctuation with our previous work based on Cluster measurements. The two spectra show similar trend with Komolgorov's -5/3 as their slopes. This may imply the similarity of the structures observed by both WIND and Cluster spacecrafts. Finally, we discuss the possible formation mechanisms for these multi-scale pressure-balanced structures. Our result is important to support the existence of multi-scale PBSs from one-hour scale down to one-minute, and is helpful to understandThis work detects multi-scale, from hour to seconds, pressure-balanced structures （PBSs） in the solar wind based on the anti- correlation between the plasma thermal pressure and the magnetic pressure measured by WIND at 1 AU on April 5th, 2001. In our former research based on Cluster measurements, we showed the anti-correlation between the electron density and the magnetic field strength in multi-scales, and we supposed these structures may be pressure-balanced structures. Thus, in this work we aim to prove our speculation by the direct evidence on pressure measurements. Different from our previous work, we apply the WIND measurements this time, for they have both the magnetic pressure and the plasma pressure which Cluster could not offer. We use the wavelet cross-coherence method to analyze the correlation between the plasma pressure （Pth） and the magnetic pressure （PB）, and also the electron density （N~） and the magnetic field strength （B） on various scales. We observe the anti-correlation between Pth and PB distributed at different temporal scales ranging from 1000 s down to 10 s. This result directly indicates the existence of pressure- balanced structures （PBSs） with different sizes in the solar wind. Further, We compare the wavelet cross correlation spectrum of Pth-PB and Ne-B. We notice that the two spectra are similar in general. Thus this result confirms that the relation between Pth-PB and Ne-B are consistent with each other in the PBSs we study. Moreover, we compare the power spectrum density （PSD） of relative Ne fluctuation with our previous work based on Cluster measurements. The two spectra show similar trend with Komolgorov＇s -5/3 as their slopes. This may imply the similarity of the structures observed by both WIND and Cluster spacecrafts. Finally, we discuss the possible formation mechanisms for these multi-scale pressure-balanced structures. Our result is important to support the existence of multi-scale PBSs from one-hour scale down to one-minute, and is helpful to

关 键 词：多尺度结构 压力平衡 太阳风 用户交换机 压力测量 等离子体压力 平衡结构 磁场强度 

分 类 号：P353.8[天文地球—空间物理学]