Overview of the widespread SEP event observed on 2013 August 19 at different spacecraft locations. (a) View from the north heliographic pole showing the locations of STEREO-A (red), near-Earth observers (L1; green), STEREO-B (blue), MESSENGER (brown) and Mars Odyssey (purple) on 2013 August 20. R and Long indicate the heliocentric distance and heliographic longitude of each observer, respectively, in the HEEQ coordinates. Also shown are the nominal IP magnetic field lines connecting each spacecraft with the Sun (yellow circle at the centre, not to scale), considering the mean solar wind measured around the solar release time of the SEP event (for MESSENGER and Mars Odyssey the same speed as measured at STEREO-A was assumed). The orange line indicates the longitude of the parent CME apex direction. (b) Particle counting rate measured by Mars Odyssey in the higher channels of the inner scintillator with the background subtracted and smoothed with a third-order polynomial regression. (c) Near-relativistic electron intensities measured by MESSENGER. (d)–(f) Near-relativistic electron (top) and proton intensities measured by STEREO-A, STEREO-B, and ACE and SOHO, respectively. The orange arrows on the horizontal axis indicate the occurrence time of the parent CME, as observed in EUV data, and the vertical orange lines show the passage of the IP shocks related with the SEP event. The shocks arriving the Earth that are not associated with the parent solar source are indicated with vertical grey dashed lines in (f). The horizontal lines in (d) and (e) represent a period with significant proton contamination of the electron fluxes observed by both STEREO/SEPT.