Spectral analysis of geomagnetically induced current and local magnetic field during the 17 March 2013 geomagnetic storm

• Published in: Advances in space research 2022-05, Vol.69 (9), p.3417-3425
• Main Authors: Xu, Wen-Hao, Xing, Zan-Yang, Balan, Nanan, Liang, Li-Kai, Wang, Yan-Ling, Zhang, Qing-He, Sun, Zi-Dan, Li, Wen-Bin
• Format: Article
• Language: English
• Subjects: Cross Wavelet Transform (XWT); Geomagnetic Storms; Geomagnetically Induced Current (GIC); Wavelet Coherence (WTC)
• ISSN: 0273-1177; 1879-1948
• DOI: 10.1016/j.asr.2022.02.025

•The CWT and DWT spectrographs of GIC and dBx/dt during the 17 March 2013 storm are very similar.•The XWT and WTC spectra of GIC and dBx/dt reveal their correlation and phase relationship for the first time.•The third-order low frequency coefficient best reflects the disturbances in GIC and dBx/dt. Geomagnetically induced current (GIC) is known to be closely related to the rate of change of local horizontal magnetic field (dBx/dt); and their spectra can give better insight into the relationship. We study the spectral characteristics of GIC measured in Finland and dBx/dt measured 30 km away during the 17 March 2013 intense geomagnetic storm (SymHMin = −132 nT). Two bursts of large GIC (up to 32A) and dBx/dt occurred at ∼16 UT and 18 UT during the storm main phase. For the first time, the cross wavelet transform (XWT) and wavelet coherence (WTC) techniques are used to investigate the correlation and phase relationship of GIC and dBx/dt in time-frequency domain. Their WTC correlation is strong (over 0.9) over the entire storm period, indicating dBx/dt is the main factor causing GIC. Their XWT spectra show two enclosed periods (8–42 min and 2–42 min) in the high energy region corresponding to the two bursts of activity in GIC and dBx/dt. Morever, we use continuous wavelet transform (CWT) and discrete wavelet transform (DWT) to analyze the spectral characteristics of GIC and dBx/dt. It is found that the CWT and DWT spectra of the two are very similar, especially in the low frequency characteristics, without continuous periodicity. Wavelet coefficients become large when GIC and dBx/dT are large; and the third-order coefficient, which corresponds to low-frequency part, best reflects the disturbance of GIC and dBx/dt.