基于小波分析的地磁甚低频脉动指数及其在高磁纬度地区甚低频脉动共轭对比研究中的应用

Wavelet-based ULF pulsation indices and their application to geomagnetically conjugate ULF pulsation studies at high latitudes

地磁甚低频脉动是甚低频磁流体波在磁层中传播的地面表现,开发近实时空间天气产品来监测这些地磁脉动至关重要。本文基于小波分析提出一种地磁甚低频脉动指数,并将其应用于研究在南极洲及西格陵兰岛的磁共轭位置观测到的地磁甚低频脉动。研究结果表明,(1)该指数可有效识别Pc4—Pc5频率范围内的脉动事件(包括瞬态事件),并获得甚低频脉动在时域和频域的重要特征。(2)基于共轭位置地磁脉动的小波分析比较揭示了冬至日、夏至日条件下南北半球甚低频脉动的相似性和差异。本研究也表明,南北半球磁共轭位置观测到地磁脉动存在的差异受到行星际磁场条件、磁场拓扑、观测磁纬度和日照等条件影响,需要进一步研究案例中实际磁层和电离层配置以及驱动条件。

Geomagnetic Ultra Low Frequency(ULF)are terrestrial manifestations of the propagation of very low frequency magnetic fluid waves in the magnetosphere,and it is critical to develop near real-time space weather products to monitor these geomagnetic disturbances.A wavelet-based index is described in this pa-per and applied to study geomagnetic ULF pulsations observed in Antarctica and their magnetically conju-gate locations in West Greenland.Results showed that(1)the index is effective for identification of pulsa-tion events in the Pc4–Pc5 frequency range,including transient events,and measures important characteris-tics of ULF pulsations in both the temporal and frequency domains.(2)Comparison between conjugate lo-cations reveals the similarities and differences between ULF pulsations in northern and southern hemi-spheres during solstice conditions,when the largest asymmetries are expected.Results also showed that the geomagnetic pulsations at conjugate locations respond differently according to the Interplanetary Magnetic Field condition,magnetic field topology,magnetic latitude of the observation,and other conditions.The ac-tual magnetospheric and ionospheric configurations and driving conditions in the case need to be further studied.