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An investigation into Geoelectric tides at three sites in the UK

Baillie, Orsi; Whaler, Kathy; Beggan, Ciaran. 2017 An investigation into Geoelectric tides at three sites in the UK. [Poster] In: European Space Weather Week 14, Oostende, Belguim, 27th November - 1st Dec 2017. (Unpublished)

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Abstract/Summary

Electric fields are created by the motions of sea water through the geomagnetic field. Continuous geoelectric field monitoring began at the UK magnetic observatories in 2012/2013 alongside the standard geomagnetic field measurements. The three observatories are in quite different settings in relation to the seas surrounding the British Isles and the new data allow investigation of any tidally generated signals. More generally, the new electric field measurements will provide ground-truth data to test the accuracy of electric field estimates calculated using the geomagnetic field data and models of the electrical conductivity structure beneath the observatories for space weather studies. In this work, an investigation into the effects of periodic phenomena has been carried out, revealing both solar and lunar signals. Firstly, superposed epoch analysis has been performed. The results for Hartland observatory are consistent with the findings of previous experiments in the English Channel, with regard to the magnitude of solar and lunar semi-diurnal (S2 and M2) variations. Secondly, frequency analysis, using the fast Fourier transform has been used to find the dominant frequencies present in the electric field data again identifying known Sq-harmonics and the dominant motion-induced M2 tidal period at each station. There are difficulties in carrying out conventional Fourier analysis because of gaps in the data. This limits the length of continuous input data sets and so the frequency resolution. To overcome this problem, we have also used the Lomb-Scargle periodogram to investigate the spectrum as this method permits gaps in the data. We have also calculated the correlation between the geoelectric field components and data from closest tidal gauge stations to each site.

Item Type: Publication - Conference Item (Poster)
NORA Subject Terms: Earth Sciences
Date made live: 16 Aug 2018 08:17 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/520735

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