Gamayunov Konstantin V, Engebretson Mark J
Department of Aerospace, Physics and Space Sciences Florida Institute of Technology Melbourne FL USA.
Department of Physics Augsburg University Minneapolis MN USA.
J Geophys Res Space Phys. 2022 Nov;127(11):e2022JA030647. doi: 10.1029/2022JA030647. Epub 2022 Nov 7.
Here, we extend the scope of the Gamayunov and Engebretson (2021, hereinafter Paper 1), https://doi.org/10.1029/2021JA029247 work by analyzing the low frequency ultra-low-frequency (ULF) wave power spectra in the Earth's inner magnetosphere during high speed stream (HSS) and quiet solar wind (QSW) driving conditions in the upstream solar wind (SW) and comparing our results to the results of Paper 1, where the statistics of ULF wave power spectra during coronal mass ejections (CMEs) are presented. The most important results of our statistical and comparative analyses are as follows. (a) During CMEs, HSSs, and QSW, the magnetic field power spectra of the transverse and compressional fluctuations are well approximated by power laws in the ∼mHz-Hz frequency range, where on average the parameters of power law fits during CMEs and HSSs are close, and those during QSW differ considerably from the respective parameters during CMEs and HSSs. (b) The dominance of the average compressional power over the average transverse power for the low frequency ULF waves during the 0 < SYM/H ≲ 25 nT geomagnetic conditions may serve as a proxy of HSSs in the upstream SW, whereas the opposite relation between the average powers is an indication of CMEs. (c) Independently of the SW driving conditions, a turbulent energy cascade from low frequencies in the ULF wave frequency range into the higher frequency range exists in the Earth's inner magnetosphere, supplying the nonthermal electromagnetic seed fluctuations needed for the growth of electromagnetic ion cyclotron waves (∼Hz) due to relaxation of unstable distributions of energetic magnetospheric ions.
在此，我们扩展了加马尤诺夫和恩格布雷tson（2021年，以下简称论文1，https://doi.org/10.1029/2021JA029247）的研究范围，通过分析高速流（HSS）和宁静太阳风（QSW）驱动条件下，上游太阳风（SW）中地球内磁层的低频超低频（ULF）波功率谱，并将我们的结果与论文1的结果进行比较，论文1展示了日冕物质抛射（CME）期间ULF波功率谱的统计数据。我们统计和比较分析的最重要结果如下。（a）在CME、HSS和QSW期间，横向和压缩波动的磁场功率谱在~mHz - Hz频率范围内可以很好地用幂律近似，其中平均而言，CME和HSS期间幂律拟合的参数相近，而QSW期间的参数与CME和HSS期间的各自参数有很大差异。（b）在0 < SYM/H ≲ 25 nT地磁条件下，低频ULF波的平均压缩功率高于平均横向功率，这可以作为上游SW中HSS的一个代理，而平均功率之间的相反关系则表明是CME。（c）与SW驱动条件无关，在地球内磁层中存在从ULF波频率范围的低频到高频范围的湍流能量级联，由于高能磁层离子不稳定分布的弛豫，为电磁离子回旋波（~Hz）的增长提供了所需的非热电磁种子波动。
