Fig. 3: Temporal variations and periodicity of brightness temperature and time derivative of SXR flux.
From: Microwave imaging of quasi-periodic pulsations at flare current sheet
a The variations of brightness temperature, Tb, the maximal values within corresponding boxes as in Fig. 4c, of the microwave sources at the flare loops (blue, Region C) and the entire CS region (red, including Region 0, 1, and 2) at the frequency of 3.4 GHz. The black curves represent the 11-second-smoothed time derivative of the GOES SXR 1–8 Å emission. The vertical dot lines mark the five instants when the resolved microwave and EUV images are shown in Fig. 2. b The same as (a) but at 8.4 GHz. c The normalized wavelet power spectrum of Tb variation of the flare loops region at 8.4 GHz and time-averaged Fourier/wavelet spectrum. The region with shallower color denotes the cone of influence (COI), under which the periods are insignificant. The black dotted contours enclose the regions with local wavelet significance higher than 95%, and the solid contours enclose the regions with global wavelet significance higher than 95%. Fitting results of the Fourier spectrum (histogram) are plotted with the blue solid line, with mean power components in blue dotted lines. The thick black line is the average wavelet spectrum. The gray solid line marks the 95% significance level of the Fourier spectrum, the red dotted line the 95% local time-averaged significance level, and the red solid line the 95% global time-averaged significance level. Fitted power-law index (s, see Formula (1)) and the least chi-square value (χ2) are shown in the lower right corner of the panel. d, e The same as (c) but for the wavelet analysis of the Tb variation in the entire CS region at 8.4 GHz, and of the time derivative of SXR flux of the flare, respectively.
