Systematic analysis of occurrence of equatorial noise emissions using 10 years of data from the Cluster mission
Systematic analysis of occurrence of equatorial noise emissions using 10 years of data from the Cluster mission
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DOI：
10.1002/2014ja020268
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发表时间：
2015-02
期刊：
影响因子：
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通讯作者：
Z. Hrbackova;O. Santolík;F. Němec;E. Macusova;N. Cornilleau-Wehrlin
中科院分区：
文献类型：
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作者：
Z. Hrbackova;O. Santolík;F. Němec;E. Macusova;N. Cornilleau-Wehrlin
我们报告的赤道噪声（EN）的排放，也被称为快速磁声波的系统分析结果。EN发生在地磁赤道附近的当地质子回旋频率和较低的混合频率之间的频率。我们的分析是基于四个集群航天器上的场波动时空分析-频谱分析仪仪器收集的数据。数据集涵盖2001年1月至2010年12月期间。我们已经制定了这些排放的视觉识别的选择标准，我们已经编制了一份在分析时间段内确定的2000多个事件的列表。星团轨道的演化使我们能够研究大范围的McIllit参数，从大约L <$1.1到L <$10。我们证明，EN可以发生在几乎所有的分析L壳。然而，在L壳低于L=2.5和L壳高于L=8.5时，发生率非常低（<6%）。EN多发生在L=3 ~ L=5.5之间，且在地磁赤道7°以内，出现率达40%。在地磁干扰条件下，这一比率进一步增加到60%以上。发生率作为磁局部时间（MLT）的函数的分析显示出强烈的变化外的等离子体磁层（峰值约15 MLT），而发生率内的等离子体磁层几乎是独立的MLT。这与EN产生于等离子体层顶区域的下午部分并且向内和向外传播的假设是一致的。
We report results of a systematic analysis of equatorial noise (EN) emissions which are also known as fast magnetosonic waves. EN occurs in the vicinity of the geomagnetic equator at frequencies between the local proton cyclotron frequency and the lower hybrid frequency. Our analysis is based on the data collected by the Spatio‐Temporal Analysis of Field Fluctuations–Spectrum Analyzer instruments on board the four Cluster spacecraft. The data set covers the period from January 2001 to December 2010. We have developed selection criteria for the visual identification of these emissions, and we have compiled a list of more than 2000 events identified during the analyzed time period. The evolution of the Cluster orbit enables us to investigate a large range of McIlwain's parameter from about L∼1.1 to L∼10. We demonstrate that EN can occur at almost all analyzed L shells. However, the occurrence rate is very low (<6%) at L shells below L=2.5 and above L=8.5. EN mostly occurs between L=3 and L=5.5, and within 7° of the geomagnetic equator, reaching 40% occurrence rate. This rate further increases to more than 60% under geomagnetically disturbed conditions. Analysis of occurrence rates as a function of magnetic local time (MLT) shows strong variations outside of the plasmasphere (with a peak around 15 MLT), while the occurrence rate inside the plasmasphere is almost independent on MLT. This is consistent with the hypothesis that EN is generated in the afternoon sector of the plasmapause region and propagates both inward and outward.