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Earth, Planets and Space
Fig. 12. | Earth, Planets and Space

Fig. 12.

From: Hodograph method to estimate the latitudinal profile of the field-line resonance frequency using the data from two ground magnetometers

Fig. 12.

(Top) Shows the the FLR frequency f R (x) obtained by applying the amplitude-phase gradient method (APGM) (Pilipenko and Fedorov, 1994; Kawano et al., 2002) to the “raw” data of the amplitude ratio and the cross phase calculated from the same data as those used in Fig. 11; the word “raw” here means that APGM was applied to the amplitude ratio and cross phase including the underground-origin component. We did so on purpose here, and the standard APGM includes the preprocessing of removing the underground-origin component (Kawano et al., 2002). See text for more details. (Bottom) Shows, just for information, the resonance width δ(x) obtained at the same time as the above f R (x) as a result of applying the APGM. Note that the sharp gradient at the edges, etc. are not real but the result of not removing the underground effect.

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