Fig. 6From: Ionospheric responses on the 21 August 2017 solar eclipse by using three-dimensional GNSS tomographyThe normalized power spectra of temporal variations in the electron density on the eclipse day at various altitudes. The black dot denotes the center frequency (period) of each pronounced wave. In order not to overlap the spectrum results at each altitude, the shift value of 0.2 is added in each altitudeBack to article page