Advantage of wavelet technique to highlight the observed geomagnetic perturbations linked to the Chilean tsunami (2010)

Abstract

The vertical component (Z) of the geomagnetic field observed by ground‐based observatories of the International Real‐Time Magnetic Observatory Network has been used to analyze the induced magnetic fields produced by the movement of a tsunami, electrically conducting sea water through the geomagnetic field. We focus on the survey of minutely sampled geomagnetic variations induced by the tsunami of 27 February 2010 at Easter Island (IPM) and Papeete (PPT) observatories. In order to detect the tsunami disturbances in the geomagnetic data, we used wavelet techniques. We have observed an 85% correlation between the Z component variation and the tide gauge measurements in period range of 10 to 30 min which may be due to two physical mechanisms: gravity waves and the electric currents in the sea. As an auxiliary tool to verify the disturbed magnetic fields, we used the maximum variance analysis (MVA). At PPT, the analyses show local magnetic variations associated with the tsunami arriving in advance of sea surface fluctuations by about 2 h. The first interpretation of the results suggests that wavelet techniques and MVA can be effectively used to characterize the tsunami contributions to the geomagnetic field and further used to calibrate tsunami models and implemented to real‐time analysis for forecast tsunami scenarios.

Near‐ and far‐field tsunamigenic effects on the Z component of the geomagnetic field during the Japanese event, 2011

“…Perturbations in the geomagnetic field induced by the tsunami have been observed by several authors [ Balasis and Mandea , ; Manoj et al , ; Toh et al , ; Utada et al , ; Klausner et al , ] and modeled [ Tyler , ; Kherani et al , ; Minami and Toh , ; Zhang et al , ; Kherani et al , ] in the previous literature.…”

“…In the present study, we focus on identifying both near‐ and far‐field tsunamigenic disturbances arising from ionospheric currents. Previous work done by Klausner et al [] has identified the tsunamigenic disturbances in the vertical component of the geomagnetic field. Likewise, presenting all three components of magnetic disturbances during the Japanese tsunami (2011), Kherani et al [] have found the tsunamigenic disturbances mainly in Z component.…”

Analysis of supersubstorm events with reference to polar cap potential and polar cap index

“…The high computational cost involving procedures in the continuous wavelet transform [ Daubechies , ; Mendes et al ., ] could be solved using an adequate discrete wavelet transform. Wavelet transform takes only discrete wavelets [ Mendes et al ., ; Ojeda González et al , ; Klausner et al ., ]. Depending on discretization outline used there can be redundant representations that can be avoided choosing orthogonal wave functions, the DWT as wavelet coefficients written as djk = 2 − j /2 ∫ f ( t ) Ψ j − k dt , where Ψ j k ( t ) = 2 − j /2 Ψ (2 − j ( t − k )), in which j is the discrete value of scale and k is the localization.…”

Ionospheric Effect of Non-Storm Hildcaa (High Intensity Long Duration Continuous Auroral Activity)

“…Besides this, it also detects the singularities presence in the signals (Domingues et al, 2005;Mendes et al, 2005). The larger and smaller values of amplitude of wavelet coefficients direct the energy deposited in the ring current and also show their localized positions (Klausner et al, 2014). The highest and lowest values of square wavelet coefficient during acute active stage and quiet condition are their indicators.…”