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Earth, Planets and Space
Fig. 5 | Earth, Planets and Space

Fig. 5

From: Estimating ionospheric currents by inversion from ground-based geomagnetic data and calculating geoelectric fields for studies of geomagnetically induced currents

Fig. 5

Surface impedance Z(ν = 0, ω) calculated using the layered-Earth model presented in Table 2 and Fig. 2. Crosses are the lowest and highest possible sampled frequencies created by the fast Fourier transform of 1-min geomagnetic data collected on 31 May 2013. Inserted is the same plot at a larger frequency range showing linear behaviours at both ends representing the bottom (low frequency) and top (high frequency) layers of the conductivity profile. All the linear behaviours of the middle layers are hidden by the nonlinear behaviour of the tangent function, compounded recursively at every iteration of Eq. (2)

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