Ground Pi-2 pulsations comprise superpositions of various modal components of shear and fast Alfven waves, field line resonance, and plasmaspheric resonances. These complex waveforms, hard to resolve with Fourier transforms are successfully characterized by wavelet techniques. Wavelet detection employs decomposition and reconstruction modes to characterize time-frequency components. Hence, suitable for the examination of the locality and complexity of natural signal patterns. The current study presents the automatic detection of Pi-2 pulsations using Daubechies and Morlet wavelet transforms. In the study, distinct Pi-2 events from CPMN stations along 210${^\circ}$ magnetic meridian were detected. Global Pi-2 pulsations with harmonious H oscillations and discrete D bays in the sub-aurora zone suggest a common source with diverse tunneling paths. Scalograms of Pi-2 undulations of the frequency band of 6.7-22 mHz were observed despite different kinds of Pi-2s. Auroral Pi-2s were highly localized in local time with clear H and D bays, implying magnetospheric-ionospheric current couplings. Latitudinal and longitudinal Pi-2 propagations are exemplified by 180${^\circ}$ phase-shift (polarization) in EWA and group delay in the mid-latitudes of the northern hemisphere. Overall, Pi-2 wave power from high to low latitudes declined with peak amplitudes of 15 nT to less than 1 nT, respectively. Finally, external influences from sea currents causing signal attenuation due to the station's proximity to the sea were also identified. To conclude, the accuracy and efficiency of wavelet analysis with no computation hassle render it a valuable tool for the study of space events in the magnetospheric community.

Yosuke Yamazaki

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This paper examines the response of the upper atmosphere to equatorial Kelvin waves with a period of ~3 days, also known as ultra-fast Kelvin waves (UFKWs). The whole atmosphere model GAIA is used to simulate the UFKW events in the late summer of 2010 and 2011 as well as in the boreal winter of 2012/2013. When the lower layers of the model below 30 km altitude are constrained with meteorological data, GAIA is able to reproduce salient features of the UFKW in the mesosphere and lower thermosphere as observed by the Aura Microwave Limb Sounder. The model also reproduces ionospheric response, as validated through comparisons with total electron content data from the GOCE satellite as well as with earlier observations. Model results suggest that the UFKW produces eastward-propagating ~3-day variations with zonal wavenumber 1 in the equatorial zonal electric field and F-region plasma density. Model results also suggest that for a ground observer, identifying ionospheric signatures of the UFKW is a challenge because of ~3-day variations due to other sources. This issue can be overcome by combining ground-based measurements from different longitudes. As a demonstration, we analyze ground-based magnetometer data from equatorial stations during the 2011 event. It is shown that wavelet spectra of the magnetic data at different longitudes are only in partial agreement, with or without a ~3-day peak, but a spectrum analysis based on multipoint observations reveals the presence of the UFKW.