SEP event on 27 May 2012 and corresponding ESP event on 28 May 2012 observed by STEREO A. From top to bottom, panel a shows the time profile of proton and electron intensities at different energy channels, as indicated in the legend in the top panel of b; the evolution of magnetic field magnitude and its components in RTN coordinates; and the STEREO/WAVES dynamic spectrum. The remaining six lower panels show the normalized data of the three electron channels using a fixed time lag parameter of (N = 180) and increasing window lengths M. Panels b and c are in the same format as panels b and c in Fig. 1. The boxes show the N and M values of each panel, and the gray-shaded box indicates the M value (among M1 to M6) that yields the most significant signal of the normalized data.