Spectral analysis of the structured type III burst observed on 12 November 2010. (a) Type III burst with triangular fine structures, observed at about 08:11 UT by the STEREO B spacecraft. The considered frequency range is from 14 to 1 MHz. The dotted red box represents the range where the time profile analysis was performed. The colored arrows in the Y-axis represent the frequencies at which the time-profiles in panel (b) were made. (b) Time profiles of triangular substructures. The colors represent the same frequencies as in panel (a).