Remote-sensing observations and in situ measurements of the 2013 August 19 CME. Right: view from the north heliographic pole, showing the positions of STEREO-A (W144), MESSENGER (W159), STEREO-B (E138), and the Earth on 2013 August 20 (DOY 232) in HEEQ coordinates. The yellow circle at the centre represents the Sun (not to scale). The dashed orange line marks the AR longitude. The orange arrow indicates the longitude of the CME apex direction (W165), and the orange lines (W121, E120) outline the width of the CME, as derived from the GCS model. The dashed black circles correspond to heliocentric distances of 0.5 R_⊙ and 1 R_⊙, respectively, while the brown circle corresponds to the heliocentric distance of MESSENGER (0.33 au). The inserted pictures show the coronagraph images as seen by COR2-A (a), COR2-B (b), and C3 (c); the images have been magnified for a better visualization. The dashed yellow curves roughly outline the CME-driven shock. Left: solar wind magnetic field measured by STEREO-A (d), MESSENGER (e), and STEREO-B (f). Top panels: magnetic field strength, and bottom panels: magnetic field B_RTN components, where RTN corresponds to the radial-tangential-normal coordinate system (e.g. Hapgood 1992). The dashed vertical lines mark the start and end of the ICME.