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