Fig. 4
From: On the characterization of tidal ocean-dynamo signals in coastal magnetic observatories
Comparison of oceanic M2 tide induced magnetic field signal parameters extracted from the residual data with least squares fitting of different harmonic sums. The left column shows the extracted amplitudes and the right column the extracted phases in dependence of analysed time series length. While solid lines show the results for the analysis conducted on the first n years of the 10 year time series (corresponding to lower x-axis), dotted lines show the analysis results for the last n years of data (corresponding to upper x-axis). Black lines in the left column show the results obtained by phasing and averaging the residual data and allows for a comparison of both methods. Please note, on the right-hand column the y-scales vary by row. This choice was made to increase presentability of the obtained results. Root mean square values of the residual data for each data point, i.e., for each the fit made with each fit function to the given time span is summarized in the Additional file 1 under Tables S6–S11