Period analysis. (a)–(e) Fourier power spectra in wave bands of CBSm 210–280 MHz, HMI LOS magnetogram, DART 238 MHz (polarization), and AIA 171 Å and 1700 Å. The lines in each panel represent the best fit (cyan) and the confidence level at 95% (magenta). The arrows outline the dominant periods above the confidence level. (f) Fourier power maps averaged over 150–210 s, obtained from HMI continuum maps. The overlaid contours outline the sunspot umbrae.