Geomagnetically Induced Current Analyzed with Wavelet Extraction
Résumé
Investigation of electrodynamic effects considering South American features is essential to extend understanding of middle- to low-latitude space weather phenomena. For retrieving magnetic contributions related to geomagnetically induced currents (GIC), a wavelet-based filtering method is verified and applied to magnetic records on the ground. The experimental data with one-minute resolution were acquired with magnetometers at two Brazilian sites, close to the South Atlantic Magnetic Anomaly, from Nov. 6 to 11, 2004. The signal intensities vary primarily under the influence of the geomagnetic disturbance periods. The performed wavelet analyses allow for a scale-dependent statistical characterization (including their cross-correlation) of the magnetospheric-ionospheric processes that affect the Earth's surface. The non-stationary magnetic signals can thus be split into coherent events and background noise by the wavelet denoising technique. The statistics and physical features of both parts are analyzed, and it is shown that the proposed treatment yields a depurated GIC signal. As a complementary result, this procedure also establishes an objective-automatic computational method for the GIC calculation treatment.