Panel a: dynamic spectrum of the type II radio burst observed on 2013 Oct 26; the harmonic emission is visible from 70 to ~30 MHz. The specific times and frequencies at which the location of the radio source is calculated are indicated with coloured triangles. Panel b: running-difference image of the CME observed with SOHO/LASCO (09:36−09:24 UT) with superposed contours of the radio sources (80%, 90%, and 95%) using the same colour code as for the triangles in panel a.