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Earth, Planets and Space
Fig. 9 | Earth, Planets and Space

Fig. 9

From: Towards probing Earth’s upper mantle with daily magnetic field variations: exploring a physics-based parametrization of the source

Fig. 9

Coefficient of determination \(R^2\) for periods P = 24, 12, 8, 6, 4.8, and 4 h for magnetic field components X and Y. \(X = -B_{\theta }\) and \(Y = B_{\phi }\) denote the north and east components, respectively. Stations for estimating the Sq coefficients are limited to mid-latitudes between \(\pm 5^{\circ }\) and \(55^{\circ }\). Two leftmost columns: \(R^2\) computed by Guzavina et al. (2019) using a spherical harmonic parameterization of the source. Two rightmost columns: \(R^2\) computed using a PCA-based parameterization of the source. The number of modes corresponds to the 99% threshold for the variance of the TIE-GCM stream function. PCA was applied to the whole 338 days TIE-GCM time series. FT segment length was taken as 24 h. Grey circles mark all days, and red pluses mark equinoctial days. The lines mark their mean values, respectively. The aa index indicates the level of geomagnetic disturbance, where a larger index stands for a more disturbed day; more details about this index can be found in Guzavina et al. (2019)

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