Analysis of the Rhode Island schumann resonance daily-average data
Source of Publication
International Conference on Atmospheric Electricity, ICAE 2014
© International Conference on Atmospheric Electricity, ICAE 2014 A variety of putative influences upon Schumann resonance (SR) signals have been evaluated for the case of a 20 year record of measurements of two magnetic-field detectors and one electric-field detector located at West Greenwich Rhode Island, U.S.A. (71.6?W, 41.6?N). The detector-specific SR signals considered are the values of the parameters of the first six modes of an eight-mode, three-parameter, Lorentzian-line-shape model. The three parameters of the model are peak-center frequency, peak-quality factor, and peak intensity. This model was used to fit the daily-average Fourier-transform intensity spectra spanning the frequency range 3 Hz - 56 Hz. This results in 54 SR signals: 3 channels × 6 modes / channel × 3 parameters / mode. We also computed an expected climatological-daily-average intensity spectra for each day and detector and fit these spectra to the above mentioned Lorentzian model. A linear regression of the observed parameters to the expected parameters finds that on average the climatological-daily-average data account for 35% of the variance (R2 = 0.35) of the original SR series, with the best fits obtained for the Lorentzian-fit parameter peak-intensity where 70% of the variance of the original series was explained. Averaging across channels and parameters, the second and third modes were best modeled by the climatological-average data, explaining 50% of the total variance; all above results are significant at the p = 0.001 level. We then subtracted the observed SR signals from the expected SR signals to generate residual SR signals. The residual SR time series display a systematic variation following the 11-year sunspot cycle. A linear regression of a nominal sunspot cycle with the residual time series averaged across all modes and channels, finds R2 values for peak-center frequency = 0.59, peak-quality factor = 0.31, and peak intensity = 0.0. Averaging the residual time series across all modes and fit parameters, the sunspot cycle is found in each channel; the R2 value for the E/W channel = 0.30, the R2 for the N/S channel = 0.37, and the R2 value for the Ez channel = 0.24 The sunspot-cycle pattern is strongest the mode 1 data (R2 = 0.48) and decreases with increasing mode number; the R2 for mode 6 = 0.15; all significant at the p = 0.001 level. We then examined various putative influences upon these residual SR signals using a variety of techniques. The results indicate that direct measures of solar activity (e.g. sunspot number and area) most strongly influence peak-center frequency and peak-quality factor (median R2 = 0.50) and less so the peak-intensity (median R2 = 0.02). Terrestrial temperature signals (e.g. Ocean temperature anomalies) influence peak-intensity (median R2 = 0.15) but not peak-center frequency nor peak-quality factor (median R2 = 0.01). We also examined the spectral characteristics of the residual SR signals. Both the peak-center frequency and peak-quality factor parameters, averaged over all of the modes and channels, display strong peaks at 11 years, 365 days, 180 days; in contrast, the peak-intensity parameter displays no similar features. This indicates that the values of the peak intensity parameter are well predicted by the global total lightning and the uniform-cavity model, while the peak-center frequency and peak-quality factor parameters are not. The values of these two parameters have a significant variation over the sunspot cycle unaccounted for by the global total lightning and the uniform-cavity model.
Boldi, Robert; Williams, Earle; and Guha, Anirban, "Analysis of the Rhode Island schumann resonance daily-average data" (2014). Scopus Indexed Articles. 1862.