Oscillatory features of the tornado prominence (the FOV is shown in Fig. 1 inside the white box). Panel a: snapshot of the Dopplergram movie at 12:30 UT. Panel b: example of the fitted Dopplergram at 12:30 UT. Panel c: period value from periodogram analysis. Panel d: period value from cosine curve approximation. Panel e: amplitude value from cosine curve approximation. Panel f: phase from cosine curve approximation (note that phase -π is equal to π radians); (panel g) Spectral power from periodogram analysis; white line limits areas with FAP = 1%, red line limits areas with a spectral power higher than 32, which is also overplotted in all panels with black, white, or red lines. A1, A2, and A3 indicate areas where the mean oscillatory parameters presented in Table 1 are calculated. Panel h: Hα intensity image with the positions of selected pixels taken as samples of Doppler signal shown in Fig. 4. Colour-bars give units of distribution of parameters. We note that 1 pixel = 0.25 arcsec. The temporal evolution of the Doppler maps in panels a and b is available in a movie online.
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